FINAL DRAFT UGANDA 
STANDARD  FDUS 888
First Edition
2009-mm-dd
 
Reference numbe  
r
FDUS 888: 2009
 © UNBS 2009 
  
Code of practice – Solar heating systems for swimming pools  
 FDUS 888: 2009 
ii © UNBS 2009 – All rights reserved
 Compliance with this standard does not, of itself confer immunity from legal obligations 
A Uganda Standard does not purport to include all necessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS  2009  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilised in any 
form or by any means, electronic or mechanical, in cluding photocopying and microfilm, without prior written 
permission from UNBS. 
Requests for permission to reproduce this document should be addressed to 
The Executive Director 
Uganda National Bureau of Standards 
P.O. Box 6329 
Kampala  
Uganda 
Tel: 256 41 4505995 
Fax: 256 41 4286 123 
E-mail: unbs@infocom.co.ug 
Web: www.unbs.go.ug FDUS 888: 2009 
© UNBS 2009 – All rights reserved  iii
 Contents Page 
Foreword………………………………………………………………………………………………..…………iv 
1   Scope ....................................................................................................................................................1  
2  Normative references ...........................................................................................................................1  
3  Definitions .............................................................................................................................................3  
4    Relevant statutory requirements .......................................................................................................5  
5    Components .........................................................................................................................................6  
6    System design .....................................................................................................................................9  
6.1    General .................................................................................................................................................9  
6.2    Design considerations ........................................................................................................................9  
6.3    Typical system designs ....................................................................................................................12  
6.4    Collector location ..............................................................................................................................1 4 
7    Thermal performance ........................................................................................................................15  
8    Electrical considerations ..................................................................................................................19  
9   Installation ............................................................................................................................... ...........20  
9.1   General ............................................................................................................................... .................20  
9.2   Pre-installation checks ......................................................................................................................20  
9.3   Plumbing and pipework considerations ..........................................................................................21  
9.4   Connections to existing filtration system ........................................................................................21  
9.5   Special considerations ......................................................................................................................22  
9.6    Heat loss mechanisms ......................................................................................................................22  
9.7   Passive pool heating ..........................................................................................................................23  
9.8   Active pool heating ............................................................................................................................25  
9.9   Plumbing schematics .........................................................................................................................26
9.10  Piping…………………………………………………………………………………………………………..43 
9.11   Flow control and safety devices .......................................................................................................44  
9.12   Instructing the homeowner ...............................................................................................................46  
10.   Commissioning, handover and documentation ..............................................................................47  
Annex A Details of the model system referred to in clause 6 for thermal performance ...........................50  
Bibliography................................................................................................................... .................................503  
 
 FDUS 888: 2009 
iv © UNBS 2009 – All rights reserved
 Foreword 
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry  of Tourism, Trade and 
Industry established under Cap 323, of the Laws of Uganda.  UNBS is mandated to co-ordinate the 
elaboration of standards and is  
(a) a member of International Organisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex A limentarius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT/SPS Agr eements of the World Trade Organisation (WTO). 
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a gi ven field or area and consists of representatives of 
consumers, traders, academician s, manufacturers, governme nt and other stakeholders. 
Draft Uganda Standards adopted by the Technical Committ ee are widely circulated to stakeholders and the 
general public for comments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council.  
Committee membership 
The following organisations were represented on Subcommittee on Solar Energy, UNBS TC 13/SC 3, in the preparation of this standard: 
• Renewable Energy Department, Minist ry of Energy and Mineral Development 
• Makerere University 
• Incafex Solar Systems 
• Battery Masters (U) Limited 
• Equator-sun (U) Limited 
• Ultratec (U) Limited 
• Sonnerkraft Solar Systems 
• Solar Masters 
• Uganda National Plumbers Association 
• Uganda Institute of Professional Engineers 
• Uganda National Bureau of Standards 
 
 FINAL DRAFT UGANDA STANDARD FDUS 888: 2009
 
© UNBS 2009– All rights reserved 1
 Code of practice – Solar heating systems for swimming pools  
1   Scope 
This Uganda Standard code gives recommendations and guidance for the design, performance, installation 
and commissioning of solar heating systems for indoor and outdoor swimming pools. 
Brief consideration is given to the thermal properties of pool covers. 
The code does not deal with the filtration systems for swimming pools to which solar heating systems are 
often connected. 
2  Normative references  
The following referenced documents are indispensable fo r the application of this Uganda Standard. For dated 
references, only the edition cited applies. For undated references, the latest edition of the referenced 
document (including any amendments) applies. 
ISO 9059:1990, Solar energy — Calibration of field pyrheliometers by comparison to a reference 
pyrheliometer 
ISO 9060:1990, Solar energy — Specification and classification of instruments for measuring hemispherical 
solar and direct solar radiation 
ISO 9459-1:1993, Solar heating — Domestic water heating syste ms — Part 1: Performance rating procedure 
using indoor test methods 
ISO 9459-2:1995, Solar heating — Domestic water heating system s — Part 2: Outdoo r test methods for 
system performance characterization and yearly performance prediction of solar-only systems 
ISO 9459-5:2007, Solar heating — Domestic water heating sy stems — Part 5: System performance 
characterization by means of whole-system tests and computer simulation 
ISO 9488:1999, Solar energy — Vocabulary 
ISO 9553:1997, Solar energy — Methods of testing preform ed rubber seals and sealing compounds used in 
collectors 
ISO 9806-1:1994, Test methods for solar collectors — Part 1: Thermal performance of glazed liquid heating 
collectors including pressure drop 
ISO 9806-2:1995, Test methods for solar collectors — Part  2: Qualification test procedures 
ISO 9806-3:1995, Test methods for solar collectors — Part 3:  Thermal performance of unglazed liquid heating 
collectors (sensible heat transfer only) including pressure drop 
ISO 9808:1990, Solar water heaters — Elastomeric materials for absorbers, connecting pipes and fittings —
Method of assessment 
ISO 9845-1:1992, Solar energy — Reference solar spectral irradiance at the ground at different receiving 
conditions — Part 1: Direct normal and hemispherical solar irradiance for air mass 1.5  FDUS 888: 2009 
2 © UNBS 2009 – All rights reserved
 ISO 9846:1993, Solar energy — Calibration of a pyranometer using a pyrheliometer 
ISO 9847:1992, Solar energy — Calibration of field pyranometers by comparison to a reference pyranometer 
ISO/TR 9901:1990, Solar energy — Field pyranometers — Recommended practice for use 
ISO/TR 10217:1989, Solar energy — Water heating systems — Guide to material selection with regard to 
internal corrosion 
FDUS 854-1:2009, Thermal solar systems and components — Solar collectors — General requirements 
FDUS 854-2:2009, Thermal solar systems and components — Solar collectors — Test methods 
FDUS 855-1:2009,  Thermal solar systems and compon ents — Factory made systems —General 
requirements 
FDUS 855-2:2009, Thermal solar systems components — Factory made systems — Test methods 
FDUS 885:2009, Standard guide for on-site inspection and verificati on of operation of solar hot water systems  
ASTM B42:2002, Standard specification for seamless copper pipe, standard sizes 
ISO 7598:1988, Stainless steel tubes suitable for scr ewing in accordance with ISO 7-1 
ISO 49:1994, Malleable cast iron fittings threaded to ISO 7-1 
ISO 4144:2003, Pipework — Stainless steel fittings threaded in accordance with ISO 7-1 
ASTM A126:2004, Standard specification for gray iron castings for valves, flanges, and pipe fittings 
IEC 60364 (All parts), Low-voltage electrical installations 
ASTM E119:2007, Standard test methods for fire tests of building construction and materials 
ASTM E861:1994(2007), Standard practice for evaluating thermal insulation materials for use in solar 
collectors 
ISO 9774:2004, Thermal insulation for building applications — Guidelines for selecting properties 
ISO 13787:2003, Thermal insulation products for building equipment and industrial installations —
Determination of declared thermal conductivity 
CISPR 14-1, Electromagnetic compatibility — Requirements for household appliances, electric tools and similar apparatus — Part 1: Emission 
CISPR 14-2, Electromagnetic compatibility — Requirements for household appliances, electric tools and similar apparatus — Part 2: Immunity — Product family standard 
ISO 9906:1999, Rotodynamic pumps — Hydraulic performance acceptance tests — Grades 1 and 2 
ISO 15783:2002, Seal-less rotodynamic pumps — Class II — Specification 
ISO 9908:1993, Technical specifications for centrifugal pumps — Class III 
ISO 9905:1994, Technical specifications for centrifugal pumps — Class I 
BS 1565-2, Galvanized mild steel indirect cylinders, annular  or saddle-back type — Part 2: Metric units FDUS 888: 2009 
© UNBS 2009 – All rights reserved  3
 BS 1566-1, Copper indirect cylinders for domestic purposes — Part 1: Specification for double feed indirect 
cylinders  
BS 1566-2, Copper indirect cylinders for domestic purposes — Part 2: Specification for single feed indirect 
cylinders 
BS EN 1057, Copper and copper alloys — Seamless, round copper tubes for water and gas in sanitary and 
heating applications 
BS 3198, Specification for copper hot water storag e combination units for domestic purposes 
ISO 4427-1:2007, Plastics piping systems — Poly ethylene (PE) pipes and fittings for water supply — Part 1: 
General 
ISO 4427-2:2007, Plastics piping systems — Poly ethylene (PE) pipes and fittings for water supply — Part 2: 
Pipes 
ISO 4427-5:2007, Plastics piping systems — Poly ethylene (PE) pipes and fittings for water supply — Part 5: 
Fitness for purpose of the system 
EAS 205, Controls for household appliances 
ISO 16422:2006, Pipes and joints made of oriented unplasticized poly(vinyl chloride) (PVC-U) for the 
conveyance of water under pressure — Specifications 
BS 4814, Specification for expansion vessels using an in ternal diaphragm, for sealed hot water heating 
systems 
ISO 15874-1:2003, Plastics piping systems for hot and cold water installations — Polypropylene (PP) — Part 
1: General 
ISO 15874-2:2003, Plastics piping systems for hot and cold water installations — Polypropylene (PP) — Part 
2: Pipes 
ISO 15874-5:2003, Plastics piping systems for hot and cold water installations — Polypropylene (PP) — Part 5: Fitness for purpose of the system 
ISO 6242-1:1992, Building construction — Expression of users' requirements — Part 1: Thermal requirements 
ISO 6242-2:1992, Building construction — Expression of user s' requirements — Part 2: Air purity 
requirements 
ISO 15493, Plastics piping systems for industrial applicat ions — Acrylonitrile-butadiene-styrene (ABS), 
unplasticized poly(vinyl chloride) (PVC-U) and chlorinat ed poly(vinyl chloride) (PVC-C) — Specifications for 
components and the system — Metric series 
IEC 61000-3-2, Electromagnetic compatibility (EMC) — Part 3-2: Limits — Limits for harmonic current 
emissions (equipment input current ≤ 16 A per phase) 
3  Definitions 
For the purposes of this code the following definitions apply. 
3.1     
collector (solar collector, solar panel) 
the general term for a device in which solar radiation is  absorbed and converted to heat which is removed by 
the heat transfer fluid. FDUS 888: 2009 
4 © UNBS 2009 – All rights reserved
 3.2   
flat plate collector 
a collector that employs no concentration of the incident  solar radiation and in which the absorbed plate is 
essentially planar. 
3.3    
embedded collector 
a collector in which the fluid passages are embedded either in the ground or within a covering such as paving 
slabs, asphalt or concrete 
3.4    
trickle collector 
a flat plate collector in which the heat transfer fluid is not contained within passageways in the absorber plate but flows down the plate surface 
3.5   
absorber plate (absorber) 
the element of a collector that receives and absorbs the solar radiation and converts it into heat 
3.6   
absorber plate surface coating 
a coating whose principal function is to absorb solar radiation 
3.7   
selective surface 
an absorber plate surface c oating that will decrease the radiative emission from the ab sorber plate whilst 
maintaining a high absorptance for solar radiation 
3.8   
unglazed collector 
a collector with the front surface of the absorber plate exposed to the surrounding air.  The rear surface may or 
may not be insulated 
3.9   
glazed collector 
a collector with an absorber plate cove red by a translucent glazing material. The rear of the absorber plate will 
normally be insulated within a weatherproof envelope 
3.10   
direct system 
a system in which the pool water passes through the solar collectors 
3.11   
indirect system 
a system in which a fluid other than the swimming pool water passes through the solar collectors 
3.12  
integrated circuit 
a system in which the solar collectors form part of t he same pipework circuit as the pool filtration plant 
3.13   
separate circuit 
a system in which solar heating circuit is comp letely separated from the pool filtration circuit FDUS 888: 2009 
© UNBS 2009 – All rights reserved  5
 3.14   
drainback system 
a system in which as part of the normal working cy cle the collector is automatically drained and refilled 
3.15   
draindown system 
a system within which heat transfer fluid is retained until manual draining takes place 
3.16   
differential temperature controller 
a device that is able to detect a sm all temperature difference and control pumps and other electrical devices in 
accordance with this temperature difference 
3.17   
pool inlet 
the point at which water from the filtration circuit is re turned to the pool, generally by means of an inlet nozzle 
3.18   
pool outlets 
the points at which water is drawn from the pool to be f iltered, generally from a sump outlet at the lowest point 
in the pool and from a skimmer outlet at  the pool surface 
4    Relevant statutory requirements 
4.1   General 
There are statutory requirements that have to be obser ved before the installation of any swimming pool. As 
these requirements may vary slightly between different parts of the countr y, the relevant local authority should 
always be consulted regarding planning and building regul ations and, likewise, the local supply authority 
regarding water supply requirements. 
4.2   Planning 
As a general rule, permission has to be obtained from the local planning authority before carrying put any 
development. Consequently, it should be ascertained from the local planning authority as to whether or not the 
proposed installation constitutes development. 
4.3   Building regulations 
General regulations have been enacted concerning the design and construction of buildings. Solar heating 
systems incorporated into buildings have to comply with these regulations in so far as they affect matters of 
construction, roof loading, weather tightnes s, fire resistance, insulation, etc. 
Advice on some of these matters is gi ven elsewhere in this co de. However, res ponsibility for the application of 
the regulations in a particular area rests with the local authority, which may require plans to be deposited, 
showing how it is proposed to comply with the regulations. 
4.4   Water supply 
Water supply byelaws for preventing wa ste, undue consumption, misuse or  contamination of water supplies 
have been made by the Water Authorities and Companies. These byelaws require that  written notice is given 
to the local water authority before installing or altering (except for repair or replacement) any water fitting used 
or to be used in connection with an existing supply of water from the undertaking. 
It should be noted that whilst the various sets of byelaw s are identical except for a few minor respects, the 
interpretation and enforcement of byelaws rests with the particular water supply authority concerned. Bearing FDUS 888: 2009 
6 © UNBS 2009 – All rights reserved
 this in mind, it is considered that to attempt to gi ve meaningful detailed guidance on the application of water 
byelaws in this code could be misleading. However, it can be assumed that where a so lar heating system is to 
be used to heat water for domestic use, as well as to heat swimming pool water, then the recommendations 
contained in US 853 should be taken into account. 
The application of the water byelaws will depend on for ex ample, whether the solar heating system (for pool 
water only) is direct or indirect, whether the heat transfer fluid is pool water, potable water or a non-aqueous fluid and how the make up water to the pool and/or solar heating system is supplied. It is therefore 
recommended that early contact is made with the local water undertaking to discuss the proposed installation 
and to seek advice. 
4.5   Other actions 
In addition to complying with the legal requirements detail ed in 4.1 to 4.4, it is recommended that the occupier/ 
owner inform the lessors, mortgagors, insu rers, etc. of the property as applicable. 
5    Components 
5.1   General 
This clause describes the principal components us ed in solar heating systems for swimming pools. 
5.2   Collectors 
5.2.1  Types of collector 
Solar collectors intended for swimming pool applications ar e commonly of the flat plat e variety but they may or 
may not be glazed and insulated. 
Embedded and trickle collectors may be used. 
Collectors are designed so that a heat transfer fluid, often the swimming pool water itself, can pass through 
the collector in close thermal contact with a matt black or similar heat absorbing surface. When the material 
used between the fluid passages is a good conductor of  heat, e.g. copper, the fluid passages can be spaced 
apart. When a poorer heat conductor is used, it is im portant to bring the flui d passages closer together. 
Table 1 – Some relevant for components and fittings 
Feed and expansion cisterns and ex pansion vessels BS 417, BS 4213, BS 4814 
Tanks and cylinders BS 1566-1, BS 1565, BS 3198 
Pumps                                                              ISO 9906 
Valves                                                              BS EN 12288 
Pipework and fittings 
Standards applicable to pipes and pipe fittings include the following 
Form and material Designation Type and application 
Tubes 
Copper 
Plastics  
BS EN 1057 
  
Hot and cold water services 
 FDUS 888: 2009 
© UNBS 2009 – All rights reserved  7
        ABS 
       PP 
      Unplasticized PVC 
      HDPE 
Stainless steel ISO 15493 
ISO 15874 
ISO 4422 
ISO 4427 
ISO 7598 Cold water services 
Hot and cold water services 
Cold water services 
Cold water services 
Hot and cold water services 
Fittings 
Copper and copper alloy 
Malleable cast iron and cast copper 
alloy 
Unplasticized PVC 
ABS  
BS 864-2 
ISO 49 and ISO 4144 
ISO 16422 
ISO 727-1  
(Capillary and compression) 
Hot and cold water services (compression) 
Cold water services (screwed pipe fittings) 
Hot and cold water services 
Cold water services 
Cold  water services 
5.2.2  Selection of collector type 
Solar collectors used for pool heating can be installed without glazing or a similar translucent cover in front of 
the absorber if they operate clos e to the ambient temperature. 
Glazing reduces the radiation incident on the absorber an d this effect may outweigh the reduction in heat loss 
from the front of the collect or. Similarly rear insulation  may marginally improve the performance but the benefit 
may be too small to warrant the additional cost.  
Unglazed and uninsulated collectors pref erably should be mounted in a position that is sheltered from strong 
prevailing winds. If such a site is not available consideration should be given to the use of glazed and insulated collectors. In the case of pools maintained at temperatures appreciably above the ambient 
temperature the incorporation of front glazing gives better thermal performance for the same collector area, 
but the improvement may not justify t he extra cost involved. The use of double glazing on the absorber is not 
likely to be worthwhile. 
In indirect systems the use of glazed and insulated co llectors may be appropriate because of the temperature 
differential across the heat exchanger. For the sa me reason the use of a selective surface may be 
advantageous. 
Trickle collectors may have the advantage of being cheap but if glazed may have a reduced performance due to the build up of algae. Evaporative heat loss from unglazed trickle collectors may substantially reduce their 
performance. 
NOTE  Other forms of collector, e.g. concentrating, evacuated and tracking collect ors, are not dealt with in this standard 
because these types are primarily used for higher temperat ure applications and insufficient experience is currently 
available about their use for pool heating . 
5.2.3  Selection of materials 
In direct systems it is important to select materials for the fluid passages that are suitable for contact with 
swimming pool water. The materials used should neither contaminate the pool water nor should they become corroded under normal service conditions. 
Plastics materials, such as polypropylene, polyethylene or EPDM, are generally suitable for contact with pool water and solar collectors manufactured from these mate rials are available. Black pigmented material is 
normally utilized and it should be ensured that the material is stabilized against degradation by ultraviolet light. 
Copper can also be used for the fluid passages in dire ct circulation solar collectors but it is important to 
maintain the pH of the pool water at between 7.2 and 7.6 or above in order to prevent corrosion. This, together with the correct total alkalinity and free residual chlorine level, will prevent undue corrosion/erosion of copper 
pipework at flow velocities up to 1.5 m/s. 
Iron and carbon steel are unsuitable for the fluid passages  because there may be rapid corrosion resulting in 
the failure of the collectors and rust staining of the pool walls and fittings. It is important to recognize that not 
all grades of stainless steel will resist corrosion in  these applications and grade 316 type is recommended. FDUS 888: 2009 
8 © UNBS 2009 – All rights reserved
 Some aluminium alloys are not suitable for direct c ontact with pool water because of the probability of 
corrosion. 
Adequate steps should always be taken to guard against bimetallic corrosion and pitting corrosion. For 
example, in indirect drainback syst ems (see Figure 3) it is important not to use galvanized steel cisterns 
combined with copper pipework since pitting corrosion of t he steel may occur. The risk is particularly high in 
systems where the heat transf er fluid is highly aerated. 
Reference should be made to US 853 regarding corrosion protection and the use of h eat transfer fluids other 
than pool water in indirect swim ming pool solar heating systems. 
5.3   Controls 
5.3.1  A control system is an important part of the swimming pool solar heating installation. The purpose of 
the control is to ensure that fluid is pumped through the collectors only when heat can be gained. 
5.3.2  In direct systems it is usual to in corporate the solar collect or circuit into the existing filtration circuit. 
This minimizes the total pumping power used for pool filt ration and for solar collection. It is often cheaper and 
more convenient than using a separate circ uit for the solar collectors (see 6.2.1). 
The filtration pump is normally required to run during times when there may be no solar heat gain. It is 
therefore preferable to be able to run the filtration plant ei ther continuously or on a time switch and to install 
the means of diverting the pool water through the solar colle ctor circuit whenever a heat gain is available. This 
can be achieved by using a valve to divert the flow thro ugh the solar collector after filtration. Thus the water 
has to pass through the solar co llectors and then back to the pool. 
Alternatively, an additional pump may be used in the sola r collector circuit which, when activated, draws 
filtered water and returns it to a point further downstream  from where it can return in the normal way to the 
pool. 
5.3.3  Whether a diverting valve or a pump is used, a co ntrol system is required to ensure that the pool 
water is only circulated through the collectors when there is a net heat gain available. An electronic differential temperature controller incorporating a pair of temperature sensors is usually used to activate the solar pump 
or diverting valve. One of these sensors detects the p ool temperature while the other detects the temperature 
of a section of the absorber plate wh ich is exposed to solar radiation but is thermally insulated and remote 
from a fluid passage. A collector sensor mounted in the fluid outlet pipe from a swimming pool solar collector 
may not be satisfactory because it may not adequately detect the relatively small temperature rises which can be considered as useful in a high flow rate system. The pool temperature sensor is normally mounted in close 
thermal contact with the water in the filtration circui t prior to the branch to the solar collectors (see 7.7). 
NOTE  In this context the net heat gain is achieved wh en the value of energy collected exceeds the cost of  energy 
expended by a separate circulating pump. The temperature differe ntial at which the controller turns the system off should 
therefore take account of any pump energy consumption. Since the relevant temperat ure differential is likely to be small it 
is important to select a controller with  limited temperature drift characteristics . 
5.4   Pool covers 
5.4.1  Heat losses from swimming pools occur mainly from  the water surface and various types of cover are 
available to reduce these losses in both indoor and out door pools. Covers can be regarded as a useful energy 
conservation measure with any type of pool and will enable many pools to function more efficiently as natural 
collectors of solar radiation. 
NOTE  Manufacturers, suppliers and instal lers should advice the swimming pool owners on the use and benefits of the 
pool cover. 
5.4.2  Various types of floating pool cover c an be used including the following types: 
a)  single skin plastics film; FDUS 888: 2009 
© UNBS 2009 – All rights reserved  9
 b)  double skin plastics film with encapsulated air bubbles; 
c)  closed cell plastics foam. 
d)  liquid bio-degradable foam  
All of these types are available in either transluc ent or opaque grades but the plastics foams are frequently 
supplied laminated onto an opaque woven material. Other co vers are available which are stretched across the 
surface of the pool above the water level. 
Covers are moved on and off the pool many times each season. Any pool cover should be sufficiently tough to 
allow necessary handling. Materials used for covers for open air pools should be adequately resistant to both 
ultraviolet radiation and to chemicals normally present in swimming pools. 
The main function of a cover is to reduce or eliminate evaporation from the surface of  the pool. All of the cover 
types mentioned are effective in this respect since they  form a vapour barrier acro ss the top surface of the 
pool. Any water lying on the top of the cover will reduce its effectiveness. With covers that are suspended 
above the water it is important to ensure that the ed ges are reasonably airtight since otherwise water vapour 
will escape. 
The second function of the cover is to prevent heat lo ss by convection. The single film covers are the least 
effective in this respect.  
The third function is to reduce the radiation heat loss fr om the swimming pool. This is the least significant heat 
loss from the surface of the pool. 
For a pool that receives sunshine and where the cover ma y be in place for even only a few daylight hours it is 
advantageous to select a translucent cover. With such covers there can still be a very significant radiation 
heat gain to the pool. Sunlight that passes through the co ver is largely absorbed by the pool water itself. The 
water can thus be heated naturally in the same way as with an uncovered pool but with the great advantage that the heat losses from the top surface are substantially reduced. 
5.4.3  Safety is an important consideration as most cove rs cannot support the weight of a child or pet 
animal. Due to the risk of drowning, no one should swim beneath a cover. This is particularly important with 
floating covers. 
6    System design 
6.1    General 
Principal design features of swimming pool solar heating systems are often determined by: 
a)  the type of pool (indoor or outdoor); 
b)  the intended period of use; 
c)  possible locations for the collectors, in part icular their height relative to the pool surface. 
In addition, the choice between a direct or indirect system is fundamental. 
Whereas satisfactory system design details may in prin ciple be determined by calculation, it is considered 
helpful to summarize the features that have been found to  be crucial to successful operation and to give a 
brief description of the most popular system types. 
6.2    Design considerations 
6.2.1  Interaction with existing equipment FDUS 888: 2009 
10 © UNBS 2009 – All rights reserved
 Any connection between swimming pool solar heati ng systems and existing filtration equipment has to be 
such as to ensure continuing satisfactory performance under all operating conditions. 
A reduced flow rate through the filtration system may re sult in inadequate filtration as well as poor mixing of 
the water in the pool. This could contribute towards increased thermal stratification in the pool with a resultant 
increase in heat loss from the pool. Moreover care shoul d be taken to ensure that there is no short circuiting of 
water between the inlets and outlets in the pool which coul d be caused by a reduced flow rate at the pool inlet 
nozzles. 
6.2.2  Collector drawback and draindown 
Many swimming pool solar heating systems need to be designed to ensure that the collectors (and often other exposed components also) may be fully drained under some conditions. Failure of components to be drained satisfactorily may, depending upon their design, result in  extensive damage. It is ther efore important both that 
the initial system design is correct and in accordance  with manufacturer's recommendations and that users 
are aware of what constitutes satisfactory behavior. 
Two common situations are as follows. 
a)  Systems in which collectors ar e located above pool level and drain whenever heat transfer fluid (usually 
pool water) is not delivered to them under pressure. Th is is the "drainback" mode of operation and is used 
typically to provide automatic frost protection or, in the case of some glazed co llectors, protection against 
boiling. 
b)  Systems in which heat transfer fluid may be retained within collectors for long periods but in which 
manual draining to preclude frost damage is necessary usually at the end of each swimming season (see 10.7). 
In order to achieve satisfactory drainback careful sy stem design is required and the following points should be 
considered. 
1)  A suitable air admittance device has to be fitted (see 6.2.3). 
2)  There has to be an unobstructed route for water to return to the pool by gravity. The closed port of a 
3-way valve can prevent water draining back from the collectors. 
3)  Water should be prevented from returning to the pool by means of reverse flow through the filter 
since this may backwash part of the debris collected by the filter into the pool. Unless the filtration 
pump is already fitted with a device to prevent reverse flow, a non-return valve should be fitted in the filtration circuit. 
4)  The pressure head in the filtration circuit may prevent complete drainback of the solar collector 
circuit. Any parts of the solar circ uit that will not be drained as a re sult of this should be otherwise 
protected against frost damage (e.g. by being located indoors) . 
5)  Means should be provided for checking whether t he system drains back as intended, e.g. by fitting a 
drain valve which would show the pr esence of water if opened [see 10.2 f]. 
Whether automatic drainback or man ual draindown is intended all pipes including collector header pipes and 
fluid passages within the collectors should be laid to adequate falls to allow complete draining e.g. a minimum of 1 in 200. Drain-off valves should be provided at any lo w points in the circuit that will not drain by gravity and 
stop valves should be provided to isolate any parts of the circuit that are designed to be left drained during 
extremely low temperatures from parts that may be left operational. 
6.2.3  Pressures in direct circuits 
There are particular considerations regarding pressures in direct circulat ion systems when solar collectors are 
installed above the pool water level. The water at the po ol surface will be at atmosp heric pressure so direct 
solar heating circuits above pool water level will be  at sub-atmospheric (negative) pressures unless FDUS 888: 2009 
© UNBS 2009 – All rights reserved  11
 maintained at a positive pressure by a pump. The pot ential reduction in pressure below atmospheric pressure 
is dependent on the height of the circuit above the pool. 
When collectors are installed up to about 1 m above pool wate r level the entire circuit is likely to be maintained 
at positive pressure when t he system circulating pump is running and will only be at negative pressure when 
the pump is switched off. In such cases the circuit may be designed to drain back in to the pool whenever the 
pump is switched off if an air admittance device, such as a suction relief valve, is incorporated into a high point 
of the circuit. Automatic air vents used for this purpose  may not be relied upon to open, especially under low 
negative pressure, if of a type held closed by flotation or by spring action. 
Where collectors are mounted at higher levels there may be negative pressures in the upper parts of the circuit even when the circulating pump is operating and th ere is a satisfactory flow rate through the solar 
collectors. In order to prevent air entrainment which ma y lead to air locking these parts of the circuit have to 
be airtight. 
In such cases drainback cannot be facilitated by means of  a suction relief valve unless it can be ensured that 
the point in the circuit at which this device is fitted is always maintained at a positive pressure while the circulating pump is operating. This may be achieved  by fitting the air admit tance device upstream of a 
restrictor valve positioned close to the highest point in  the circuit but a significantly higher pump loading may 
result. 
Alternatively, an air admittance device in the form of an electrically operated "normally open" valve wired in 
parallel with the pump may be used in a circuit that is other wise airtight. In this case particular care has to be 
taken to ensure that ai r in the circuit will be expelled on refill by virtue of water velocity an d the return pipework 
should be sized accordingly. 
If frost protection is to be achieved by manual drai ning an automatic air admittance device need not be fitted 
but the system components have to be specified to  withstand sub-atmospheric (negative) pressures. 
6.2.4  Circulation of heat transfer fluid 
In direct solar heating circuits the heat transfer fluid (pool water) may be circulated through the collectors by 
either the filtration pump or a separate pump. In the latter case the solar heating circuit may either be connected to the filtration circuit or be remote from it with separate inlet and outlet connections to the pool. 
In indirect systems optimum flow  rates will depend much on the deta iled efficiency and pressure loss 
characteristics of the heat exchanger. Whilst the figures given can serve as a guide, manufacturers' 
recommendations should be studied, also with a view to ensuring that neither the co llector nor heat exchanger 
efficiency is unduly compromised under typical work ing conditions. Similarly, pumping power should be 
considered at an early stage in design. 
The efficiency of all thermal solar collectors decrease s with increasing operating temperature and this is 
particularly severe for unglazed units. It is therefore impo rtant that the flow rate of  heat transfer fluid is 
sufficiently high to help ensure efficient operation. In  practice a flow rate for water of 0.04 kg/(m2.s) of collector 
is usually satisfactory; flow rates above 0.06 kg/(m2.s) produce little additional benefit and will incur higher 
pumping energy requirements. Glazed collectors can work with little loss of efficiency at lower flow rates, 
typically 0.02 kg/(m2.s) to 0.04 kg/(m2.s) for water. 
6.2.5  Pipe sizing and distribution 
It is particularly important to ensure balanced flow dist ribution to all collectors within a pool heating system, 
especially if unglazed collectors are used. In addition to the usual calculations for pressure loss along flow and 
return pipes the following special factors should be considered at the design stage: 
a)  alternative collector interconnection schemes such as reverse return pipework layouts, having regard to 
manufacturers' recommendations; 
b)  the possible need to install balanci ng (restrictor) valves especially if banks of collectors are to be sited at 
different heights in a drainback system; FDUS 888: 2009 
12 © UNBS 2009 – All rights reserved
 c)  the need to ensure posi tive subsequent filling of all collectors following draining, e.g. by ensuring that air 
cannot be trapped in one or more banks of collectors; 
d)  the need to size pumps for drainback systems to ov ercome the total static lift in addition to overcoming 
the frictional losses in the circuit. 
6.2.6  Direct circuits 
Pool water can be contaminated with suspended solids and other debris which could block solar collectors 
and associated pipework. It is therefore important to ensur e that only filtered water is passed through the solar 
collector circuit. This is easily achieved in the case of solar circuits connected to the filtration system, provided 
that water is diverted to the collectors after the filter. However, in circuits not integrated with the filtration 
system it is necessary to provide an adequate level of f iltration prior to circulation through the solar collectors. 
This may be achieved by fitting a suitable mesh strainer  over the outlet connection from the pool or by fitting 
an in-line strainer elsewhere in the circuit but the design  has to allow for access for cleaning or provision be 
made for back-washing. Such pool outlet connections are best kept clear of the sump of the pool or the water 
surface since suspended matter and debris tends to accumulate at these locations. 
6.2.7  Indirect circuits 
In indirect circuits the pool water is passed through  the secondary side of a heat exchanger located in the 
filtration circuit. The solar collectors are connected to t he primary side of the heat exchanger and heat transfer 
fluid is circulated by means of a separate pump. 
The heat transfer fluid used in the primary circuit may contain a suitable corrosion inhibitor and/or anti-freeze 
solution to provide frost protection. In sealed circui ts heat exchange oils may also be used. Manufacturers' 
advice regarding the use of dissimilar metals and t he suitability of components such as pumps should be 
sought particularly when using non-aqueous fluids. 
It is recommended that the corrosion inhibitor and/or anti-freeze solution should be non-toxic and also contain 
non-toxic biocide compounds to prevent bacteria and algae growth in the primary heat transfer fluid. 
6.3    Typical system designs 
6.3.1  Direct circulation with separate pump not connected to filtration circuit 
Flow and return connections to the pool should be positioned to ensure good mixing with the pool water. The 
pump may be either located below the pool water level so t hat it is kept full of wate r at all times (and protected 
from frost by being located indoors or by manual drai ning in extremely low temperature period) or be self-
priming. 
Since these systems are not connected to the filtration circuit autom atic drainback may be achieved 
conveniently in most situations. 
6.3.2  Direct circulation with separate pump integrated with filtration circuit 
A typical circuit is shown schematically in Figure 1. T he solar pump is positioned so as to draw filtered water 
from the filtration circuit and therefore the pump does  not normally need to be self-priming. The connection 
from the solar collector circuit should be positioned so as to introduce solar heated water ahead of any 
chemical dosing equipment or auxiliary heating plant. Dr ainback for frost protection may be achieved provided 
that the pressure head in the filtration circuit is insuffi cient to hold water in exposed parts of the solar heating 
system. 
6.3.3  Direct circulation with flow diversion by 3-port valve 
A typical circuit is shown schematically in Figure 2. A 3- port valve may be installed in the pool filtration circuit 
with one of the two outlet ports connected to a llow circulation through the solar collectors. FDUS 888: 2009 
© UNBS 2009 – All rights reserved  13
 The pipe from the solar collectors should be connected in to the filtration circuit such that flow is maintained 
through any dosing equipment or auxiliary heater. 
In order to provide automatic control 3-port valves ar e normally fitted with an actuator motor connected to the 
solar heating control system. Since the outlet port to the solar collectors will normally be closed when the 
filtration pump is switched off (often by a time switch) a drainback system will only f unction satisfactorily if a 
means to bypass the closed port of the motorized valve is introduced. 
 
Figure 1- Direct circulation with separate pump integrated with filtration circuit 
6.3.4  Indirect circuits 
Three typical types of indirect circuit are as follows. In each case the solar collectors should be connected to 
the primary side of a suitably sized heat exchanger with the pool water passing through the secondary side 
(see 7.6). 
a)  Drainback circuits. These incorporate a drainback cistern situated in a location secure from frost and 
below collector level but above the level of the circ ulating pump (see Figure 3). An air admittance device 
which may take the form of an air break at the drainb ack cistern should be insta lled in the circuit. A float 
operated valve usually controls the level of the water in the cistern and it shoul d be recognized that the 
float may become submerged during the drainback condition.  It is important that the cistern has sufficient 
reserve capacity that the level does not reach either the cistern overflow or the inlet valve. Such systems 
can provide frost and boiling protec tion to the solar collectors. 
b)  Sealed and pressurized circuits. These incorporate conventional pressurized sealed circuit equipment 
such as expansion vessels and pressure relief valves. Su ch circuits allow great flexibility to the designer 
regarding acceptable collector positions in terms of he ight relative to the pool. The use of a suitable heat 
transfer fluid may remove the risk of freezing or boiling. 
c)  Feed and vent cistern circuits . These may be designed in a similar way to conventional forced 
circulation central heating systems.  The cistern should be located above the solar collectors,; so this type FDUS 888: 2009 
14 © UNBS 2009 – All rights reserved
 of system is particularly suitable where solar collecto rs are mounted at low level. The use of a suitable 
heat transfer fluid can offer frost protection. The vent ing arrangement should be designed to allow for the 
discharge of any generated steam. 
6.4    Collector location 
6.4.1  General 
The most suitable location for the solar collectors should be determined by considering the implications on 
thermal performance, pipework connections and the vis ual appearance of alternativ e available positions but 
having regard to the need for access for inspection and maintenance. 
 
Figure 2- Direct circulation with flow diversion by 3-port valve 
NOTE  The pipe circuit requirement s are described in 6.2 and 6.3 
The effect on thermal performance of different collecto r locations will depend on their relative exposures to 
both solar radiation and to wind. Generally collectors should be installed in unshaded positions orientated and 
inclined to intercept a maximum amount of solar radiat ion. Guidance on the optimum orientation and angle of 
tilt is given in Clause 7. The effect of exposure to  wind will be more pronounced for unglazed collectors and a 
sheltered position is therefore to be preferred. 
Pipework lengths should be kept to the minimum possi ble so as to reduce both pumping power requirements 
and heat losses. The latter will be unimportant with pipe work operating at low temperatures but will become 
more significant as the temperature rises. Standard calculation methods ar e available to estimate pipework 
heat losses and these should be used to help determine the optimum thickness of any insulation. The thermal 
insulation and method of installation should comply with ISO 9774. 
6.4.2  Collector fixing FDUS 888: 2009 
© UNBS 2009 – All rights reserved  15
 The method of fixing solar collectors has to be considered carefully taking into account the considerable 
forces caused by wind lift to which collector fixings  may be subjected. Manufacturers' recommendations 
regarding fixing systems should be followed and where such fixings are to be fastened to other building structures, special attention should be paid to the design of the fixings and the load that they may place on the 
building structure. 
Fixings should not be liable to corrode, cause rainwate r leaks or work loose because of wind vibration. The 
advice of a suitably qualified person should be sought where appropriate. 
Where fixing battens or similar items are to be used on flat  or sloping roofs, these should always be spaced off 
the roof or otherwise arranged so t hat they do not interfere with the nor mal drainage of rainwater on the roof. 
Reference should be made to US 853 for collector installation practices. 
 
Figure 3 – Typical indirect drainback circuit 
7    Thermal performance 
7.1    General 
The predictions of performance are based on computer si mulations which are described in detail in Annex A. 
In these simulations, the central assumptions are that: 
a)  the collectors are part of a di rect system; that is, the pool water passes through the collectors; 
b)  the collectors face south at 45° to the horizontal; FDUS 888: 2009 
16 © UNBS 2009 – All rights reserved
 c)  there is auxiliary heating to maintain the pool water at a fixed temperature so that the temperature of the 
pool water entering the collector is constant. 
The amount of collector area to be chosen for a giv en application will depend upon the heating requirements 
for the pool concerned. These requirements will be det ermined by the size of the pool, the desired water 
temperature and the degree to which the pool cover is  used. For outdoor pools the heating requirements are 
also strongly affected by the location of the pool, particularly its exposure to wind. For indoor pools the 
temperature and humidity levels of the air in the pool ha ll will strongly influence the pool heating requirements. 
 
Pool temperature (oC) 
Data set: Kew 1959 to 1979 
Energy integrated over January to December 
NOTE  The performance of collectors, particularly those of  type 3, will depend on many factors and these curves 
should be interpreted with reference to Clause 6. 
Figure 4 — Average energy output from collectors for a typical year 
7.2   Collector type 
It is the characteristics of the collector employed that are of primary importance in determining the thermal 
performance of the system. Typical val ues of these are given in Annex A, fo r three types of flat-plate collectors 
commonly used for solar heating swimming pools: a single-gl azed insulated selective co llector (collector 1), a 
single-glazed insulated matt black collector (collector 2); and an unglazed, uninsulated collector (collector 3). When these collectors are used, the energy output, or heat transferred to the pool water, over a typical year is 
as shown in Figure 4. Figure 5 shows the output over a typical sw imming season, taken here to be the period 
May to September inclusive.  
NOTE  In this context a typical year is one in which the weather corresponds closely to the long-term average weather. 
7.3   Pool water temperature 
The performance of a solar collector, especially if it is unglazed and uninsulated, is strongly dependent on the 
temperature of the pool water. The effect of pool wate r temperature on typical ener gy outputs of the different 
types of collector is shown in Figure 4 and Figure 5. FDUS 888: 2009 
© UNBS 2009 – All rights reserved  17
 7.4   Positioning of the collector 
The heat output varies with the orientation and tilt of the collector, which will often be determined by the site. 
However, the predicted variation is slight. It can be assu med, all other factors being equal, that the output will 
be at least 90 % of that shown in the figures if the collector faces anywhere between 30° east and 40° west of 
true south and is tilted from the horizontal between 20° and 50°. 
 
Pool temperature (oC) 
Data set: Kew 1959 to 1979 
Energy integrated over May to September 
NOTE  The performance of collectors, particularly those of type 3, will depend on many factors and these curves 
should be interpreted with reference to Clause 6. 
Figure 5 — Average energy output from collectors for the period May to September inclusive 
Shading from trees, buildings, etc., can produce a signif icant decrease in system performance, and collectors 
should be positioned to minimize this. Undue exposure to wind will also reduce the performance, particularly 
of unglazed collectors. Conver sely, if unglazed collectors are mounted in a very sheltered position, energy 
output may be increased above that indicated. 
7.5   Climate 
The heat output figures quoted are annual averages calcul ated with the meteorological data for Kew (UK) over 
the 21 year period from 1959 to 1979. The change in weather from year to year may cause variations of up to 15% from the long-term averages for glazed collector s. For unglazed collectors there will be an equal or 
greater variation in performance from year to year. 
Even in a given year, differences in performance may occur between similar systems in the same locality 
because of variations in local conditions, for example, exposure to wind. FDUS 888: 2009 
18 © UNBS 2009 – All rights reserved
 7.6   Indirect systems 
For an indirect system the heat transferred to the pool water will be reduced because the temperatures in the 
collector circuit will be higher than for a direct system, to provide a temperature differential to operate a heat 
exchanger. The actual reduction fo r a given system would depend on the effectiveness of the heat exchanger 
used and will be larger if unglazed collectors are used t han if glazed collectors are used. It should be noted 
that heat exchangers not specifica lly designed for low temperature di fferentials will prove unsuitable. 
7.7   Other factors 
The flow rate through the collector should be fairly high so that the temperature rise  across the collector is 
kept low and thus the heat losses are minimized. This  is especially important if collectors are unglazed. 
Recommendations for flow rates are given in 6.2.4. 
The temperature differential between the pool temperature se nsor and the collector sensor at which circulation 
through the collector is allowed to occur can affect  the amount of energy supplied. If the flow rates 
recommended in 6.2.4 are used, the temperature differentia l settings should not be critical. However, it is 
suggested that the temperature difference at which circulation starts should not exceed 2 K and the 
temperature difference at which it is st opped should not exceed 1 K (see 5.3.3). 
7.8    Collector sizing 
7.8.1  General 
Methods for calculating the heat requirement for indoor pools have been developed. Caution should be 
exercised when applying these methods for the calculation of heat losses from outdoor pools. The effect of 
wind speed is most significant but it is not easy to quantify due to its dependence on the amount of shelter 
provided around the pool. Wind breaks such as hedges or fencing improve the comfort of bathers and reduce heat losses from the pool. 
7.8.2  Indoor or outdoor pools with auxiliary heating 
Whilst the installed area of the collector may often be influenced by available sp ace, a convenient starting 
point is to calculate the area necessa ry to provide all the heat required in  the month for which the requirement 
is lowest. It can then be assured that the system will rare ly produce heat that is surplus to requirements. When 
the average rate of heat loss from the pool is known, perhaps from previous fuel bills, Figure 6 may be used to determine an appropriate collector area. This figure refe rs to the calculated long-term average performance of 
collectors operated at Kew-UK  for the month of July. 
For months other than July, the heat supplied by the collector will be less than that needed to maintain the required temperature. The auxiliary heating system is used  to keep the pool temperature at the design value. 
In that case, the contribution provided by the collector towards the heat requirement may be determined from Figure 4 or Figure 5, according to the period over which the pool is in use. 
It may happen that the collector heat output is required to  be known for individual months other than July, for 
example where systems are operated at schools or holiday camps. This may be estimated from additional figures given in Annex A. 
For pools in use only from May to September there may be a significant further collector output obtained during the warm-up period (typically du ring the month of April). The collector  should be allowed to pre-heat the 
pool before the pool is brought into use, with the pool cover left in position to reduce heat loss. The cost of 
running any pump should be considered when determining th e most appropriate length of pre-heat period. 
The auxiliary heating system should then be turned on as la te as possible, working at its full capacity to bring 
the pool water quickly up to the desired temperature. 
7.8.3  Outdoor pools without auxiliary heating 
When auxiliary heating is not provided, the pool temperature will vary both from day to day and from month to 
month. The variation for a given pool will depend on the local weather conditions and the amount of shelter FDUS 888: 2009 
© UNBS 2009 – All rights reserved  19
 provided. If outdoor swimming is desired over the May to  September season, the following ratios of collector 
area to pool area appear to be satisfactory, provided that a pool cover is used. 
Location   Ratio of collector area to pool area 
Sheltered   0.5 
Exposed   0.8 
The area required for this application does not depend mu ch on the type of collector employed, since the pool 
temperature is normally in the region for which the collector energy output is approximately the same for all 
collector types. 
 
Pool temperature (oC) [Data set:  Kew 1959 to 1979] 
NOTE  The performance of collectors, particularly thos e of type 3, will depend on many factors and these 
curves should be interpreted with reference to Clause 6. 
Figure 6 – Average energy output from collectors for July 
8    Electrical considerations 
8.1   General 
The electrical component of the system shall be designed and installed in accordance with relevant 
regulations and standards. Due care and consideration should be given to the environmental conditions when 
selecting equipment for use. 
8.2   Electrical installation 
All wiring and apparatus shall be installed in accordance with the requirements of  IEC 60364. All plant and 
equipment shall comply with relevant Uganda Standards. FDUS 888: 2009 
20 © UNBS 2009 – All rights reserved
 8.3   Electrical safety 
The Uganda Wiring Regulations  require that any wiring and apparatus ar e properly installed and protected to 
ensure safety, particularly from the effects of fire  and shock. This protection is achieved by adequate 
insulation of all conductors and apparatus and the provis ion of effective earthing arrangements. It should be 
ensured that, in the event of a fault, the installation is automatically disconnected from the supply within 0.4 s. 
Additionally, protection may be provided by the installation of an appropriate type of residual current circuit 
breaker. 
8.4   Controls 
Controls shall be in accordance with  the requirements set out in EAS 205. 
8.5   Avoidance of electrical interference 
Where applicable, the requirements given in IEC CI SPR 14 and IEC 61000-3-2 shall be complied with, to 
avoid interference with other systems. 
8.6   Testing 
All electrical wiring and apparatus associated with a swimming pool solar heating system has to be inspected 
and tested to confirm the correct polarity, the effectiveness of the earthi ng and the adequacy of the insulation. 
Residual current circuit breakers should  be tested regularly and an advisory notice to this effect prominently 
displayed. 
9   Installation 
9.1   General 
Designers of solar heating systems for swimming pools should supply sufficient information to the installer to 
enable satisfactory installation and commissioning. It should not be assumed that the installer has specialist 
knowledge beyond that of general plumbing and heating practice. 
A record should be kept by the installer of any necessa ry design or layout changes agreed with the purchaser. 
9.2   Pre-installation checks 
The client or his agent should confirm to the installer that clearance of the stat utory requirements has been 
met prior to commencement of installation. The installati on contractor should ensure that he has all necessary 
system design information including: 
a)  the required location of the solar collectors t ogether with mounting or fixing details as appropriate;  
b)  design details relating to the height of the collectors above pool level and any  necessary arrangements 
for air purging and/or draining of the collectors; 
c)  details of the pipework layout, with particular r egard to interconnection to any existing system and to the 
factors considered in 6.2.5; 
d)  instructions for setting up any balancing valves so as  to ensure an evenly distributed flow of fluid through 
the collectors; 
e)  in an indirect system, the spec ified type, source of su pply and required concentration of heat transfer 
fluid, together with any special system  cleaning, testing or filling procedures; FDUS 888: 2009 
© UNBS 2009 – All rights reserved  21
 f)  details of electrical works including cont rol and earthing arrangements for both existing and new 
equipment. 
It should be checked that the proposed collector arrangement and pipework r outes are practicable and that all 
components for the installation are available. It should also be checked that the existing pool filtration and 
circulation equipment are in good working order. 
9.3   Plumbing and pipework considerations 
The manufacturer's recommendations regarding the interconnection of collectors should be followed. All 
pipework and collector interconnections should be designed to accommodate thermal movement having 
regard especially to the high stagnation temperatures that may be attained in bright sunlight. These temperatures are not expected to exceed the following: 
selective glazed surfaces      200 °C 
black glazed surfaces        150 °C 
black surfaces sheltered from wind       90 °C 
The installation of the pipework and fittings should be carried out in accordance with good plumbing practice, 
particular attention being given to the following. 
a)  Adequate support and fixing should be provided for t he pipework to ensure that all levels and falls are 
maintained, and the spacing of the fixings are such as  to limit sagging of the pipe between the supports. 
Means should be provided to accommodate therma l expansion and contraction of the pipework. 
b)  Individual support should be provided to heavy components such as pumps, and motorized valves. 
Pipework used to support other components should be adequately secured. 
c)  Unions or flanged joints should be provided on each connection to pumps and motorized valves to allow 
the removal and replacement of the device without the need to cut the pipework. 
d)  The fall of the pipes should be arranged to allow th e installation to be reliably drained and vented. Low 
points, when unavoidable, should be fitted with drai n valves and high points should be fitted with air 
vents. 
e)  Where collectors are mounted directly on the ground, e.g. paving with embedded circulating pipes, or are 
formed beneath the ground surface, e.g. pipe s embedded in asphalt, the foundation should provide 
sufficient support to prevent movement which might  damage pipework connections and be capable of 
supporting the dead weight of the covering and any expected traffic load without damage. 
9.4   Connections to existing filtration system 
If the solar heating system is to be integrated with the existing pool filtration system, the following recommendations apply. 
a)  To minimize alteration to the existing pipew ork, the flow and return connections to the 
b)  The connection to the solar collector is fitted to  the existing pipework after the filter and before the 
auxiliary heater (if one is fitted). 
c)  The isolating valves on the flow and return pipe s for the solar system should be fitted close to the 
connection points into the filtration circuit. 
d)  It should be ensured that pumps, motorized valves and non-return valves are mounted in an acceptable 
plane with the flow in the correct direction. 
e)  Where pumps or motorized valves have to be installed in an exposed position, suitable weather 
protection should be provided unless they ar e specifically designed for outdoor use. FDUS 888: 2009 
22 © UNBS 2009 – All rights reserved
 f)  No thermal insulation should be applied to an installation before an adequate test is carried out to 
 ensure that the system functi ons correctly without leakage. 
9.5   Special considerations 
The provisions for fixings and the foundations for any support frame should be inspected and supervised by a 
competent person. 
Wherever possible an opaque heat resistant covering ma terial, e.g. a tarpaulin, should be applied temporarily 
to collectors to avoid the high temperature rise which can occur should the unfilled collector be exposed to direct sunshine during installation. Care should be ta ken to avoid burns which can occur when the bare arms 
or other exposed skin come into contact with any metal or other parts of the collector which may become 
heated by solar radiation during installation. Apart fr om the burns, the shock may be sufficient to cause 
distraction and possible loss of foot hold on the roof or supporting frame. 
9.6    Heat loss mechanisms 
9.6.1  Evaporative losses 
The rate of evaporation from a pool surface is dependent upon wind velocity, air temperature, relative humidity 
and pool water temperature. 
Warm water evaporates more rapidly than cool water. Up to 70 % of a swimming pool's heat energy loss 
results from evaporation of water from its surface. Evaporative losses ar e directly proportional to wind 
velocities at the pool surface and are higher from warm pools than from cooler pools. 
Because most of the heat loss from a swimming pool is caused by evaporation of water from the surface, 
every effort should be made to reduce the evaporation process. Air temperature and relative humidity (both of 
which influence the rate of evapor ation) are beyond our control. 
9.6.2  Convective losses 
Convective losses occur when air cooler than the pool water blows across the pool surface. The layer of air 
that has been warmed by contact with the water is carr ied away by the wind and repl aced with cooler air — a 
process that continues as long as the air is in motion.  Detailed observations show the heat energy lost from a 
pool in this fashion is directly proportional to the wind speed at the surface — doubling when the air velocity doubles. 
Windbreaks such as hedges, trees, solid fences, buildings and mounds should be placed so as to shield the 
pool from cool winds. 
9.6.3  Radiative losses 
Swimming pools radiate energy directly to t he sky, another important energy loss mechanism. 
Even with a small difference in temperature between t he pool surface and the sky, radiative losses may 
exceed 10 % of the total swimming pool energy losses. 
9.6.4  Conductive losses 
Since a swimming pool is in direct contact with the ground or air around it, it can lose heat energy by conduction. The amount of energy transferred even fr om above ground pool walls to the air is quite small 
compared to the amount lost from the pool surface to the air. Dry ground and concrete are relatively good 
insulators, so the energy lost through the sides and bottom of  an in-ground pool is also small. In fact, much of 
the energy conducted into the ground during the day is  recovered when the pool temperature drops slightly 
during the night. In general, conductive losses th rough the walls of in-ground pools may be ignored. FDUS 888: 2009 
© UNBS 2009 – All rights reserved  23
 However, pools immersed in groundwater that is influence d by tidal motion will lose an increased amount of 
energy through their walls. Heat flows from the pool to  the ground-water surrounding it. As the groundwater is 
moved by the tides, it will be replaced pe riodically by cooler water. The quantit y of heat loss in this situation is 
higher than for pools in dry ground and is not negligible. This loss is still low compared to losses through 
evaporation, convection and radiation. 
 
9.7   Passive pool heating 
The use of passive techniques is the simplest and most cost-effective method of keeping swimming pools warm. A passive solar system is one in which the heat flows naturally — without the assistance of pumps and 
fans. Every effort should be made to incorporate the fo llowing three features in new pool construction to 
minimize the expense of supplementary energy for pool heating: 
1.  Place the pool in a sunny spot. 
2.  Reduce the wind velocity at the pool surface with suitable windbreaks. 
3.  Use a pool cover when the pool is not in use to minimize evaporation losses. 
Swimming pools themselves are very effective solar energy collectors. The water absorbs more than 75 percent of the solar energy striking  the pool surface (Figure 8). If possible, locate the swimming pool so it 
receives sunshine from about three hours before until thr ee hours after solar noon. During this time period, the 
sun's rays travel through a relatively short atmos pheric path and thus are at their maximum intensity. 
Additionally, there is less tendency for the sun's rays to  be reflected from the pool surface during midday than 
during early morning and late afternoon, because they st rike the pool surface at a small angle of incidence. FDUS 888: 2009 
24 © UNBS 2009 – All rights reserved
 
 
Figure 8 – The swimming pool as a solar collector 
9.7.1  Screen enclosures 
Screen enclosures reduce the amount of solar energy that st rikes the pool surface.  When the sun shines 
perpendicularly to the screen material, only about 15 % of t he energy is obstructed sinc e the screen area is 85 
% open air space. However, when the sun strikes the material at an angle, much less of the radiation gets 
through, and the amount available to warm the pool is reduced by as much 30-40 % on a clear day. More 
auxiliary energy will be required to maintain comfor table swimming temperatures if the pool has a screen 
enclosure. 
9.7.2  Wind speed reduction 
Reducing wind velocity at the water surface reduces c onvective and evaporative losses. Solid fences or tall 
hedges located close to the pool perimeter are effectiv e windbreaks. Buildings, trees and mounds also protect 
the pool from the cooling effect of prevailing winter winds . Locate the pool to take maximum advantage of 
these obstructions, being careful they do not shade the water surface from the sun. Windbreaks are 
particularly desirable near the ocean or adjacent to lakes, where the average wind speed is higher than in 
more sheltered locations. Figure 9 shows an example of a well-shielded pool. 
 
Figure 9 – A well-protected pool 
9.7.3  Pool covers 
Pool covers are effective in reduci ng heat losses. There are two basic types of pool covers on the market 
today: opaque and transparent. By reducing evaporation they reduce the quantity of chemicals needed, and 
they help to keep dirt and leaves out of the pool. P ool covers also reduce pool maintenance costs. 
9.7.3.1  Transparent pool covers 
Transparent covers will not only reduce evaporative losses but they will also turn the pool into a passive solar 
collector. Sunlight passes through the cover material and is absorbed by the pool water. FDUS 888: 2009 
© UNBS 2009 – All rights reserved  25
 Because evaporation accounts for about 70 % of pool heat loss, the beneficial effect of pool covers can be 
dramatic. 
Transparent pool covers are made from a variety of materials, such as polyethylene-vinyl copolymers, 
polyethylene and polyvinylchloride (PVC). 
Attention to a few details will extend the life of transparent pool covers. They should not be left folded or rolled 
up on a hot deck or patio. The sunlight will overheat t he inner layers and may even burst the air pockets in 
bubbled covers. When removing or installing a pool cover,  avoid dragging it over the pool deck or any rough 
surface or sharp obstruction. Although it is reco mmended that a single, continuous pool cover be used 
whenever possible, the use of sectioned covers can ease handling in the case of larger pools. 
9.7.3.2  Liquid films 
Materials like cetyl alcohol spread to form a layer only  a few molecules thick on a water surface. They can 
reduce evaporation by nearly 60 percent. Of course t he materials offered for this purpose are not toxic but 
they are fairly expensive and must be re-dosed frequently (usually at the close of the daily swimming period). 
The chemical films do not reduce convective or radiation losses, but they do allow solar gains. 
9.7.3.3  Opaque covers 
Opaque covers are useful for pools that must remain uncovered during daylight hours. Most commercial pools 
fall into this category. The following types of opaque covers are the most common: woven, plastic safety 
covers; skinned, flexible foam covers; and rigid or se mi-rigid closed cell foam blocks or blankets. The woven 
safety covers will reduce evaporation losses (if th ey float and are waterproof) though not as well as a 
continuous film type cover. Skinned foam covers vary in  thickness from less than 1/8 inch to more than ½ 
inch. In common insulating terms, their effectiveness in reducing heat losses ranges from R-1 to R-4. If they fit 
snugly to the edges of the pool, they will virtually el iminate evaporation losses during the periods when they 
are in place. Foam block covers such as expanded po lystyrene have insulating values between R-4 and R-12, 
depending on their thickness. If properly fitted and placed on the pool surface, they, too, will nearly eliminate 
evaporation losses during the hours they are used. Thei r effectiveness in reducing convective and radiative 
losses increases directly with their R-value.  
9.8   Active pool heating 
Many types of solar collectors are suitable for pool h eating. The temperature difference between the water to 
be heated and the surrounding air is small, so expensive insulating boxes and transparent covers that reduce collector heat loss are not often required. Cool winds above 10 km/h substantially reduce the efficiency of 
unglazed collectors. 
9.8.1  Low-temperature collectors 
Types of low-temperature colle ctors include black flat-plates, black flexible mats (both with passages for pool 
water) and black pipes. 
9.8.2  Flat-plate collectors 
Several types of flat-plate collectors,  specifically designed for pool heating, are available in both plastic and 
metal. 
Flat-plate collectors for pools feature large-diameter headers at each end and numerous small fluid 
passageways through the plate portion. The header's primary function is to distribute the flow of pool water 
evenly to the small passageways in the plate. The header  is large enough to serve as the distribution piping, 
which reduces material and installation labor costs. The fluid passageways, which collect energy from the entire expanse of the surface, are small and are spaced close together acro ss the plate (if it is made of 
plastic) so most of the collector surface is wetted on its back side. Representative cross sections of plastic 
collectors are shown in Figure 10. EPDM flexible mat collectors have the same general cross section, as do 
plastic collectors. FDUS 888: 2009 
26 © UNBS 2009 – All rights reserved
 
 
Figure 10 - -Typical collector designs 
High water flow rates also tend to keep collector-to-ai r-temperature differences low. The total amount of 
energy delivered to the pool (the most important variable) is the product of the amount of water flowing 
through the collector multiplied by the water's temperature rise. Five hundred gallons of water raised 1°F contains as much energy as 10 gallons of water raised 50°F , but the collector operating at 10°F above pool 
temperature will operate less efficiently. Thus, high flow rates increase colle ctor efficiency. Many 
manufacturers frequently recommend a flow rate as high as one gallon per minute for each 10 square feet of collector area. But such high flow rates are not needed to keep the temperature rise in the collectors below 
10°F for best efficiency. Higher flow rates result in high-pressure drops across the collector array. This 
requires an increase in the horsepower of the circulating pump. Thus, flow rates are usually limited to about 
one gallon per minute for each 10 square feet of collect or area for the configurat ions shown in Figure 10. 
Because even plastic pool heating collectors are expensive, the plastic used must withstand years of exposure to sunlight. The ultraviolet portion of sunli ght can break chemical bonds in most plastics and will 
eventually destroy the material if t he process is not retarded. Collector manufacturers use several proprietary 
combinations of additives or stabilizers and UV inhibitors  in the chemical mix of the collector material. These 
stabilizers and UV inhibitors provide protection from the damaging radi ation and retard degradation of the 
plastic in addition to improving the collector's ab ility to absorb and conduct the sun's energy. Accurate 
estimation of plastic durability is difficult; therefore, explicit warranties are desi rable. Most manufacturers 
currently offer a five-year or longer limited warranty. Some plastic collectors are expected to last 25 years. 
Plastics are available in numerous formulations and types , many of which are relatively immune to attack from 
common chemicals. Polypropylene, acrylonitrile-butadien e-styrene (ABS), polyethylene, polybutylene, 
polyvinylchloride (PVC) and ethylene-propylene with diene monomer (EPDM) are frequently used collector 
materials. Some have been used to make pool collectors for more than 20 years and have demonstrated their ability to withstand attack by swimming pool chemicals and sunlight for at least that period of time. 
Flat-plate collector designs utilizing metals are slightly different from plas tic configurations. Metal is a better 
heat conductor, so relatively long fins can separa te the tubes without causing excessive operating 
temperatures on portions of the collector surface. 
9.9   Plumbing schematics 
9.9.1  Flow control devices 
Solar pool heaters are generally connected to existing  pool plumbing systems. This section explains how to 
make the connections. 
A schematic of a frequently used pool filtration loop is  shown in Figure 11a. The pump draws the water from 
the skimmer and main drain, forces it through the filt er and returns it to the pool through the conventional 
heater. Lint, hair and leaf catching strainers are usually installed ahead of the pump. 
Solar systems designed to operate with small pressure losses can be added as shown in Figure 11c. A 
spring-loaded check valve is installed downstream from the filter to prevent collect or water from backwashing FDUS 888: 2009 
© UNBS 2009 – All rights reserved  27
 through the filter and flushing trash into the pool from t he strainer when the pump is shut down. A manually 
operated or automatic valve is placed in the main line bet ween Ts that feed the collector bank and return the 
solar heated water (Figures 11b and 11c). Ball valves may be placed in the feed and return lines for isolating 
the solar system from the pool filtra tion system when the filter is be ing backwashed or when adjustments are 
being made to the solar system. When solar heating is desired, the pump timer is adjusted to operate during 
daylight hours, and the valve in the main line is closed so mewhat to restrict or fully interrupt the flow and force 
water up through the collectors. Valves on the lines  to and from the solar system should be fully open. 
Closing the valve in the main line may increase flow th rough the collectors. It may seem logical to reduce the 
flow rate through the solar array to make the return water warmer, and this can be done; however, it is not 
logical — the collectors will be forced to operate at hi gher temperatures, their efficiencies will drop, and less 
solar energy will be delivered to the pool. The temperature rise through the collectors should be kept low, less 
than 10°F on warm, sunny days, unless the manufacturer's specifications call for a higher temperature differential. 
Forcing water through the solar system uses some of t he pump's power, thus reducing the flow rate through 
the pool filtration system. As the main line valve is closed, pressure on a gauge mounted on the filter or 
discharge side of the pump will rise slig htly. If the valve is closed entirely, all of the flow is diverted through the 
solar array and the collection efficiency increases. If the pressure at the filter does not rise unduly, the solar 
system should be operated in this way. However, the more the pressure rises, the slower the flow through the filtration system. This will increase the length of time r equired for the entire pool's co ntents to be filtered. Thus, 
it may be necessary to allow some of the flow to bypass  the collectors. An inexpensive plastic flow meter can 
be used on the main line connection to monitor flow rates through the filtration system. Check with local building officials to determine minimum filtration flow rates or pool turnover times required in your area 
When the existing pool pump lacks enough power to circul ate sufficient flow through the solar system and the 
filtration system, a booster pump may be required. It should be installed as shown in Figure 11d. Common pool-circulating pumps with or without the strainer  basket are suitable for this application. 
The booster pump should be placed in the line feeding the so lar collectors, not in the main circulation line. In 
this position it will operate (consuming electricity) only when circulation through the solar collectors is wanted. 
Of course, the booster pump may be operated by the same  time clock as that for the filter pump, but more 
often it will have a separate control. If both pumps operate from the same ti mer, it should be set so the pumps 
come on during daylight hours. In this case, the time r must be rated for the sum of the circulation pump and 
the solar booster pump. 
If the booster pump is separately cont rolled, the filter pump may run for a longer portion of the day, and the 
booster pump should turn on during appropriate pe riods but only when the filter pump is operating. 
Manual flow control or control with time clocks is simple and inexpensive but has drawbacks. Since clocks do not sense weather conditions, the circ ulating pump may be running when there is insufficient solar energy 
available to warm the pool water. Collectors may lose energy rather than gain it if weather conditions are 
unfavorable. Automatic flow controls overcome this difficulty. The most common plumbing schematic for 
systems using these devices is shown in Figure 12. FDUS 888: 2009 
28 © UNBS 2009 – All rights reserved
 
 
Figure 11 – Plumbing schematics FDUS 888: 2009 
© UNBS 2009 – All rights reserved  29
 
 
Figure 12 – Automatic control plumbing schematic 
Accurate differential temperature control is difficult to achieve because of the small temperature rise that takes 
place in solar pool heaters. A sensor, tapped into the pipi ng at a convenient place ahead of the collector return 
line, measures the pool water temperature. Another sens or is housed in a plastic block and placed near the 
solar collectors, so its temperature pa rallels that of the collector (or it may be attached to the collector outlet). 
When the pool water temperature exceeds the collector temperature, the control valve remains in the open 
position and the flow bypasses the collector loop. When the collector temperature exceeds the pool water 
temperature, the valve is closed, forcing the flow through the collectors. In practice it has proven equally 
effective to control the flow through the collectors wi th a single solar sensor, which turns on the solar pump 
and/or activates the diverting valve above a fixed solar intensity level. 
When operating properly, a differential controller auto matically adjusts to changing conditions, monitoring 
variations in collector temperature caused by clouds,  other weather factors and the approach of evening. 
When collector temperature drops, the control de-ener gizes the valve and flow bypasses the collector. 
Maximum pool temperature limits can be programmed into some controls. 
Control valves may be actuated hydraulically or el ectrically. One of the earliest valves used was a 
hydraulically operated pinch valve co nsisting of a cylinder with an expandable bladder inside. A high-pressure 
line connected to the discharge side of the pump is used to expand the bladder, pinching off the flow and 
diverting it through the solar system . A low-pressure line connected to the suction side of the pump deflates 
the bladder and allows the flow to pass unimpeded. An  automatic controller accomplishes switching between 
the high- and low-pressure lines. 
Electrically operated valves are also used. A differentia l controller may be used to operate a solenoid that, in 
turn, activates the main valve in much the same way the pinch valve is activated. Be sure the valve you select 
is specifically designed and constructed for use on pool  systems. Automatic control schematics, taken from 
the installation diagrams of two low-temperature co llector manufacturers are shown in Figures 15 and 16. 
The most common method to divert the flow of water to  the solar collectors from the pool is to use a 3-way 
valve on the solar supply line. Similar to the in-line ball va lve or isolation valve, the three-way diverter valve is 
commonly used in the swimming pool and spa industries. 
Some of the 3-way manual valves are made to be us ed for solar pool heating. The 3-way valve has a 
motorized diverter that attaches to  the top of the valve to convert the manual valve into an automatic or 
motorized valve. Other 3-way diverter valves are manufa ctured with the motor assembly on the valve. In this 
case, a differential controller sends low voltage power to the diverter actuator (or motor) and rotates the valve 
sending the water from the filter to the solar collectors. A check valve a fter the 3-way valve allows the solar FDUS 888: 2009 
30 © UNBS 2009 – All rights reserved
 collectors to drain into the pool when the pump is not operating. This may provide freeze protection if the 
system tilt and piping was installe d to allow continuous drainage. 
 
Figure 13 – Plumbing schematic 
 
Figure 14 - Plumbing schematic FDUS 888: 2009 
© UNBS 2009 – All rights reserved  31
 9.9.2  Corrosion problems 
Improper pool chemistry can cause accelerated corrosion. The pool water pH should normally be maintained 
between 7.4 and 7.8. Under acid conditions (low pH), chlo ride and sulfate ions in the pool combine with water 
to form acids capable of breaking down protective f ilms. Low pH also accelerates the corrosion of most 
metals. 
Excessive concentrations of copper ions in pool water ma y lead to the formation of colored precipitates on the 
pool wall if the pH is allowed to drop. Since many common algaecides are based on copper compounds, the 
concentration of free copper ions in pool water may relate to the use of these chemicals as well as the 
corrosion of copper piping materials. Care should be exercised in maintaining proper pH levels whether copper or plastic piping is used in a solar pool heater. 
9.9.3  Sizing filter pumps and pipe runs 
For simple installations, sizing the filters, pumps and pipe runs to circulate and keep the necessary pool water 
clean and heated may be successfully accomplished by following the instructions contained in the following 
sections. 
9.9.4  Sizing filtration and circulation systems 
Proper sizing of swimming pool filters, circulation pumps and pipe runs may be accomplished by using the 
information provided in this section in conjunction wi th data routinely provided by manufacturers of those 
components. 
9.9.4.1  Filter sizing graphs 
Filter sizing is accomplished by using graphs, such as  Figure 15, provided by filter manufacturers. The 
following types of filters are those most  often used to keep swimming pools clean. 
Sand, gravel or anthracite filters are sometimes operated at a flow rate as high as 20 gallons per minute 
(gpm)/ft2. It should be noted that some code jurisdictions limit  the flow rate through these filters to three 
gpm/ft2. Diatomaceous earth (DE) filters usually operate well at about two gpm/ft2. Both sand and DE filters 
may be cleaned by backwashing and discharging the dirty water into a sewer or other appropriate outlet. An 
air gap in the discharge line is often required to en sure against backflow contam ination from the sewer. 
Cartridge filters are usually operated at a flow rate of about one gpm/ft2 and may be reverse flushed and 
reused. When the cartridges become exce ssively dirty they are simply replaced FDUS 888: 2009 
32 © UNBS 2009 – All rights reserved
 
 
Figure 15 – Diatomaceous earth filter sizing graph for flow rate of 2gpm/ft2
In pool filtration systems, the need for cleaning is indicated by high readings on a pressure gauge, which is 
located between the filter and the pump. Filter manufact urers specify the readings at which they recommend 
maintenance. The pressure drop due to properly sized clean filters is us ually about five psi. The backwashing 
valve assembly on DE and sand filters may add another five psi. 
9.9.4.2  Pump sizing graphs 
To size the pumps it is necessary to establish a flow rate in gpm and then add up all the pressure drops that 
occur when water flows through the system at that rate. Figure 16 is a graph on which pressure drop and flow 
rate are plotted for typical swimming pool circulation pumps. 
 
 FDUS 888: 2009 
© UNBS 2009 – All rights reserved  33
 9.9.4.3  Sizing connecting piping 
Connecting piping may be sized using pipe flow charts (Figures 18 and 19). Piping should be large enough to 
prevent excessively high flow rates that cause eros ion of interior pipe and fitting surfaces. Some code 
jurisdictions limit the rate of water flow through copper  pipes to five feet per second. Adequately sized piping 
and pumps help reduce maintenance and operating costs. 
 
Water Flow Rate, Gallons Per Minute 
NOTE  Fluid velocities in excess of 5 to 8 ft/sec. are not usually recommended  FDUS 888: 2009 
34 © UNBS 2009 – All rights reserved
 
 
Examples 
The following examples are intended to help clarify sizing procedures. 
The owner of a 20-by-40-foot swimming pool with an aver age depth of 4.5 feet wants to circulate the total pool 
volume through the filtration system in eight hours. (The turnover rate is currently one complete recirculation 
per eight hours.) The owner plans to use a DE filter and  wants to know what size filter and pumps will be 
required (1) with no heater, (2) with a gas heater, (3) with a solar heater and a gas heater for back-up and (4) 
with a solar heater without a back-up. The pump will be loca ted so the center of its impeller is three feet above 
the surface of the pool. One hundred feet of pipe will be required unless so lar collectors are used. In that 
case, 200 feet of connecting pipe will be required. The high point of the solar collector array will be 12 feet FDUS 888: 2009 
© UNBS 2009 – All rights reserved  35
 above the center of the pump impeller. The solar collectors will be connected to the circulation piping as shown 
in Figure 12b. The owner also wants to know what si ze connecting pipe should be installed under any of the 
four alternative conditions. 
STEP 1: Determine the pool volume. 
Pool volume (gal) = 20' × 40' × 4.5' × 7.48 gal/ft2 = 26,900 gal. 
STEP 2: Determine the DE filter cross sectional area if 2 gpm/ft2 of filter area is an acceptable flow rate 
through it, and the pool volume of 26,900 gallons must turn over every eight hours. 
Figure 15 shows a cross sectional area between 27/ft2 and 33/ft2 will be required. The filter that 
provides 33/ft2 of cross sectional area will be the better choi ce because it will allow a turnover time of 
slightly less than eight hours. 
STEP 3 : Determine the flow rate through the filtration system. 
Because the entire volume must turn over once each eight hours, 
  Flow rate = 826900 = 3360 gallons per hour (gph) 
  Flow rate = 603360 = 56 gpm 
STEP 4 :  If no heater is included in the system, determine the total pressure, which the pump will be required 
to overcome at a flow rate of 56 gpm. 
Pressure drop Cause of pressure drop source of information 
Lbs/ln2 (Psi) Ft of water (Psi x 231) 
100 ft 1-1/2” schedule 40 
plastic pipe Figure 12 8 18.5 
Fitting About ½ of pipe drop 4 9.2 
Valves Manufacturer’s spec. 5 11.6 
Filter Manufacturer’s specs. 5 11.6 
Lift head   3 
Total   54 
 
 Figure 16 shows a one-hp pump (of the specific design covered by that graph) will circulate 56 gpm 
against a 57-foot head. A ¾ hp pump will circulate only 45 gpm against a 51-foot head, so the one-
hp pump will be the safest choice. 
 Discussion – It is interesting to note if 2-inch schedule 40 pipe is used, the pressure drop in the pipe 
is only three psi or seven feet of water, so the tota l pressure drop is about 37 feet of water. Figure 16 
shows a ¾ hp pump is powerful enough to circulate 52 gpm against a total head of 37 feet of water. (Turnover time increases to 8.6 hours) . Figure 11 illustrates the relative magnitude of the pressure 
drops. 
STEP 5 : Determine the size pump that w ill be required if a gas-f ired pool heater is added which causes an 
additional pressure drop of five psi. 
Pressure drop  Cause of pressure drop 
Psi Ft of water 
100 ft 1-1/2” schedule 40 plastic pipe 8 18.5 
Fitting 4 9.2 
Valves 5 11.6 FDUS 888: 2009 
36 © UNBS 2009 – All rights reserved
 Filter 5 11.6 
Pool heater 5 11.6 
Lift head  3 
Total  65 
 
Figure 16 shows a one-hp pump will pump about 50 gpm  against 65 feet of water. This is probably 
close enough to the required volume for practical pu rposes. (The turnover time is a littler longer — 
nine hours.) 
Discussion: Under these conditions, using two-inch pi pe reduces the total pressure drop to about 50 
feet of water but this does not allow us to us e a 3/4-hp pump because the smaller pump will only 
circulate 46 gpm against a 50-foot head. (In this case, the turnover time would be increased to 10 
hours should the 3/4-hp pump be used.) 
STEP 6 :  Determine the size pump that will be required if  we add a solar collector system and a gas-fired 
back-up heater. A pressure drop of two psi is expected across the solar collectors. The system contains an extra 100 feet of pipe and a vacuum breaker located 12 feet above the center of the 
pump's impeller. 
Using 11/2” and 2” pipe 
Pressure drop Cause of pressure drop 
Psi Ft of water 
100 ft  of 1 1/2” pipe 8 18.5 
Fittings for 1 ½” pipe 4 9.2 
100 ft of 2” pipe 3 6.9 
Fittings for 2” pipe 1+ 2.3+ 
Valves 5 11.6 
Filter 5 11.6 
Solar panels 2 4.6 
Gas heater 5 11.6 
Static head (3” + 12”)  15 
Total  92 
 
Using Only 2” Pipe 
Pressure drop Cause of pressure drop 
Psi Ft of water 
200 ft  of 2” pipe 6 13.9 
Fittings for 2” pipe 3 6.9 
Valves 5 11.6 
Filter 5 11.6 
Solar panels 2 4.6 
Gas heater 5 11.6 
Static head (3” + 12”)   15 
Total  75 
 
Figure 17 shows if 100 feet of 1-1/ 2-inch pipe and 100 feet of two-inch pipe are used to make the 
connections, a two-hp pump will move only 35 gpm against the 92-foot water head. This increases the turnover time to about 13 hours, so a 2 1/2-hp pump will be required. If 200 feet of two-inch pipe 
is used, a 11/2-hp pump will move 52 gpm against the 75-foot head. Again, in this example, 52 gpm will probably turn the pool volume over in an acceptable period of time (8.6 hr). 
Discussion: Another option applicable to retrofitting a gas-heated pool piped initially with 1-1/2-inch 
pipe and a one-hp pump is the addition of a second small pump installed as pictured in Figure 5d. FDUS 888: 2009 
© UNBS 2009 – All rights reserved  37
 The additional pump will be required to overcome a static  head of 12 feet of water and a friction head 
of 28 feet of water if 11/2-inch pipe is used to c onnect the solar panels to the system. The pressure 
loss across the panels will still be 4.6 feet of wate r. The total pressure drop, which the added pump 
will be required to overcome, will be 12 + 28 + 4.6 or about 45 feet of water head. Figure 10 shows a 
3/4-hp pump will circulate 49 gpm against a 45-foot  head. It should be noted the two pumps working 
in series will assist each other and in most case s the turnover times will be no more than eight hours. 
Two pumps require more maintenance than does one, but the solar booster pump may be turned off when circulation through the panels is not desired. This reduces electrical consumption. 
A final option for pool heating is the addition of solar co llectors without a fossil-fir ed back-up system. Referring 
to the immediately preceding piping options, the eliminati on of the gas-fired heater reduces the pressure drop 
from 92 to 80 feet of water if an additional 100 feet of 1-inch pipe and 100 feet of 2-inch pipe are used to make 
the connections. 
Figure 16 shows a 2-hp pump will pump 54 gpm against an 80-foot head. (The turnover time is 8.3 hours.) 
If 2-inch connecting pipe is used throughout, the total pressure drop is reduced to about 63 feet and a 1 hp pump will deliver 50 gpm against a 63-foot head (the turnover time is nine hours). A 1.5 hp pump will circulate 
about 65 gpm against a 63-foot head (the turnover time is 7 1/2 hours). 
Table 2 presents each of the pool heating options and the corresponding pipe and pump sizes which yield the various pool turnover time periods. 
Table 2 – Pool heating options 
Components Pipe size Pump size 
required Turnover time (in 
hours) 
100 ft of 1 ½” schedule 40 plastic 1 hp 8 System with no heater 
100 ft of 2” schedule 40 plastic ¾ hp 8.6 
100 ft of 1 ½” 1 hp 9 System with gas or oil heater 
(5 psi pressure drop) 100 ft of 2” 1 hp 7.2 
100 ft of 1 ½” plus 100 ft of 2” 2 ½ hp 8 
200 ft 1 ½” 2 pumps (1 hp 
+3/4 hp) 8 System with gas and solar (15 ft static head) 
200 ft 2” 1 hp 8.6 
100 ft 1 ½” plus 100 ft 2” 2 hp 8.3 
1 hp 9 System wit solar only (15 ft static head) 
200 ft 2” 
1 hp 7.5 
None of the steel options after the turnover rate of the pool sufficiently to require resizing the De filter. It should contain between 27/ftp
2 and 33/ftpp2 of filtration area. 
9.9.5 Pressure drop across the valves and fittings 
Many swimming pool installers use the simple rules of thumb cited in the previous examples to determine 
pressure drops caused by the resistance to liquid flow of valves and filters. However, it is important for the 
solar installer to realize the actual pressure drops vary with both flow rate and mechanical characteristics of 
specific valves and fittings. Table 3 presents frictional losses expressed in equivalent lengths of pipe for 
commonly used fittings. (Most fitting manufacturers supply sim ilar tables.) The sum of the equivalent length of 
all the fittings on the circulation system may be added to  the actual length of pipe in the system before the 
pressure drop is read from Figure 18 (plastic pipe) or  Figure 19 (copper pipe). The pressure drop across the 
backwash valve assembly is accepted as being five psi in t he example. Actually, this pressure also varies with 
flow rate and the mechanical design of specific valves. T he variation from valve to valve is too great to make a 
generalized tabular presentation of pressure drop much mo re useful than the five psi rule of thumb value. FDUS 888: 2009 
38 © UNBS 2009 – All rights reserved
 Most filter and backwash valve suppliers can make ava ilable accurate tables or graphs for their valves. The 
information is usually given in psi, which may be converted to feet of water head  by multiplying by 2.31. 
Table 3 – Fittings – Friction losses expressed as equivalent lengths of pipe (feet ) 
Type of fitting Material 1 1.2
5 1. 5 2 2.5 3 3.5 4 5 6 8 10 12 
steel 6 8 9 11 14 16 - 20 26 31 40 51 61 
plastic 9 12 13 17 20 23  29 - 45 - - - standard tee with 
flow through 
branch Copper 6 8 9 11 14 16 16 20 26 31 40 - - 
 
Steel 1.7 2.3 2.8 3.6 4.2 5.2 - 6.8 8.5 10 14 17 20 
Plastic 3 4 5 7 8 10 - 12 - 17 - - - 90 degree long 
radius elbow, or 
run of standards tee Copper 1.7 2.3 2.8 3.6 4.2 5.2 6.1 6.8 8.5 10 14 - - 
 
Plastic 3 3 3 3 3 3 - 3 - 3 - - - 
Copper 1 1 1 1 1 1 1 1 1 1 1 - - Adapter 
slip/solder fitting 
to thread insert coupling Plastic 3 3 3 3 3 3 - 3 - 3 - - - 
 
Gate valve (fully 
open) - .60 .80 .95 1.1
5 1.4 1.6 1.9 2.1 2.7 3.2 4.3 5.3 6.4 
Swing check 
valve - 7 9 11 13 16 20 23 26 33 39 52 67 77 
Ordinary 
entrance - 1.5 2.0 2.4 3.0 3.7 4.5 5.2 6.0 7.3 9.0 12 15 17 
 
9.9.6  Energy conservation 
The solar heater for a swimming pool should be sized to provide enough heat to satisfy the purchaser. 
Virtually all installers and purchaser s can agree to that. However, the sola r installer's resp onsibilities do not 
stop there. The system he or she in stalls should not increase the electrical consumption of the pool's 
circulation system any more than absolutely necessary . This requires large enough pipe diameters to keep 
their friction losses low, proper flow through the solar collectors to maximize heat collection yet minimize 
pressure drop, and adequate collector sizing to minimi ze the number of hours t he pump must operate each 
day. Obviously, it is pointless to oversize the sola r-related components to an ext ent that reduces the time 
required for heat collection below that required for acceptable filtration. 
9.9.7  Collector installation 
Acceptable solar collector mounting practices are di scussed in this section. Because unglazed, low-
temperature collectors are most often used for swi mming pool heating in Florida, procedures for mounting 
unglazed plastic flat-plate collectors, flexible solar mats and pipe arrays will be discussed first. 
The optimum collector slope for spring and fall operation is equal to the latitude of the site. The best slope for 
winter is the latitude plus 15° and th e collectors should face south if possibl e. If roof space, which faces within 
45° of south, is available, the collectors can be mo unted directly on the roof. Remember that only a small 
penalty is paid for modest deviations from optimum slo pe or orientation. Supports can be constructed to 
mount collectors at the ideal orientat ion, but except in new constructi on, the additional cost is generally 
prohibitive. Occasionally it may be necessary to increase the collector area to compensate for less than 
optimum slopes or orientations. 
Collectors should be securely fastened to withstand ma ximum expected wind loads typically from 160 to 240 
km/h. Check the local building regulations for wind load provisions in your area. 
Procedures — To begin the installation, lay out the collectors on the available roof area avoiding as much as 
possible any area shaded by trees, parts of the buildi ng or other obstructions. If large numbers of collectors FDUS 888: 2009 
© UNBS 2009 – All rights reserved  39
 are involved, they may have to be divided into several bank s with collectors in each bank plumbed in parallel. 
Plumbing arrangements from bank to bank ar e discussed in the next section. 
Once the placement is established, the collectors should be connected. Short, flexible couplings made of 
EPDM or butyl rubbers often are used. They usually  are slipped over the ends of the headers and are 
clamped firmly with stainless steel clamps. Once fastened together, the collectors are cumbersome to move 
about. Be sure they're in their final positions before the connections are made. 
Collectors often are mounted directly on the roofs. An insulating support structure is sometimes used to 
protect the panels from abrasive roofing materials and  prolong their life by protecting the bottom of the 
collector from the abrasion caused by expansion and cont raction of low temperature collectors. Refer to the 
manufacturer recommended installation procedure. 
Collectors should be laid on the roof and fastened down at the header on both ends. At least two, and 
preferably three, cross straps should span the panel to further secure it. 
Figure 21 shows one possible arrangement. Once again, refer to the manufacturer's recommended 
installation procedures. 
One end of the panel can be fastened to the roof with a short strap or clamp around the header. The other  
end should be fastened with an elastic material or spring to allow for expansion as the collector temperatures 
change — a 10-foot plastic collector may expand and contract as much as an inch in length. Straps should be 
installed across the panel body — one at either end — within a foot of the headers, and one across the middle are recommended. The straps should be made of material, such as nylon or plastic-coated metal that will not 
scratch or abrade the collector since they will rub acro ss its surface. The bands should be snugged to clips 
fastened approximately an inch from the edge of the collector. 
 
Figure 21 – Collector hold-down straps 
Figure 22 shows a typical mounting clip, which may be ma de of rigid plastic or metal. On asphalt shingle 
roofs, the clips may be fastened directly on top of the shingles — 1/4-inch lag bolts long enough to penetrate the roof sheathing are generally recommended. In k eeping with good construction practice, the lag screws 
should be screwed into as many roof rafters as possible (rather than just roof sheathi ng) to keep the collectors 
secure. A pilot hole should be drilled for the lag screw and after the drill chips are cleared away a sealant 
should be injected with a cartridge gun into the hole. An excess of sealant should be used to form a seal FDUS 888: 2009 
40 © UNBS 2009 – All rights reserved
 between the mounting clip and the roofi ng material when the lag bolt is tightened. Polysulfide and the newer 
polyurethane sealants adhere well to common building materials and appear to be very durable . 
 
Figure 22 – Typical collector mounting clip 
Sealing mounting brackets on tar and gravel (built-up roofing) requires careful cleaning around the bracket. 
Scrape off the old gravel down to the tar, and clear off all dirt and residue. If the tar surface is very dirty or 
irregular, soften it with a solvent such as mineral spirits.  After sealing the clip with polysulfide, pour roofing tar 
over the bracket base and cover with gravel. This last step is necessary to prevent ultraviolet damage to the 
tar and premature roof failure. 
Mounting collectors on other roof types is more difficult. On cedar shake roofs, mounting screws should pass through the shakes and fasten securely to the plywo od or purlins beneath. Don't be stingy — use good quality 
sealant and enough of it to form a good, sealed penet ration. Don't tighten the fasteners tight enough to split 
the shake. 
Concrete tile roofs, especially common in south Flor ida, present special mounting difficulties. The safest 
solution is to construct a rack to support the collector s above the tile surface. The rack should be constructed 
of a durable material, such as aluminum. It should be strong enough to withstand maximum anticipated wind loads. Substrate and collectors may be  fastened to the rack. The rack itself must be securely fastened to the 
roof trusses, not to the sheathing. This practice should also be used when installing a reverse pitch rack on 
the backside of a roof. 
Figure 23 illustrates a typical mounting bracket arrangemen t. To install the bracket, a tile must be removed or 
broken, exposing the waterproof membrane on the sheathing below. This waterproof surface (commonly called slate), not the tiles, forms the moisture barrier and must be resealed where mounting bolts penetrate it. FDUS 888: 2009 
© UNBS 2009 – All rights reserved  41
 
 
Figure 23 – Mounting bracket for tile roofs 
The mounting location should be free of dust and debris. Roofing mastic should be applied to the bracket and 
slate to form a seal when the bracket is drawn down. (Pitch pans around the roof penetrations may be 
required in some areas.) A substitute for the broken tile may be made from cement mix (using adjacent tiles 
as a model) and tinted to match the roof. Aluminum and copper materials should be protected from contact 
with the cement by a layer of tar to reduce corrosion. 
Fastening schemes have been proposed which rely upon sealing the roof penetration at the tile surface. Since 
the waterproof membrane is not the tile itself but rather the slate membrane b eneath, these methods are not 
effective and should be avoided. 
Spanish or barrel tile roofs present another tough collector mounting problem. It is extremely difficult to walk 
on them without breaking some tiles, and it is also difficult to make substitute tiles. 
9.10    Piping 
Solar swimming pool collectors are designed to operate with high flow rates; therefore, the primary objective in 
piping solar systems is to provide uniform, high-volume flow at the lowest cost and the lowest pump power possible. 
9.10.1  Piping to collectors 
For low-temperature collectors, plastic pipe can be used in the plumbing from the pool pump to the solar collectors. PVC and ABS pipe are the mo st commonly used materials for this particular applic ation and have 
performed satisfactorily. Neither material can withst and high temperatures. Due to the moderate operating 
temperatures, pipe insulation is not required. 
Local plumbing requirements should be adhered to when installing piping leading to and from the collectors. 
Since large-diameter pipe is quite heavy when filled with  water, sturdy supports will be required. Pipe cuts 
should be deburred before assembly to reduce resist ance to flow. Leaks can be avoided by using the correct 
cement for the pipe involved and properly preparing joints. Because plastic expands and contracts considerably with temperature changes, allowances shoul d be made for change in length. Your pipe supplier 
can provide you with specific data on the kind of pipe used for a particular job. 
9.10.2  Piping between collectors 
About the same amount of water should pass through each collector. On large installations it is necessary to 
divide the solar collecting panels into groups and connect t he groups with pipe. This requires the piping layout FDUS 888: 2009 
42 © UNBS 2009 – All rights reserved
 be carefully designed and constructed. Most situati ons encountered can be satisfied using principles 
discussed in this section, but for extremely complicated cases it may be wise to  consult a hydraulic flow 
specialist. 
Pool heating collectors are almost alwa ys connected in parallel. Parallel connections are shown in Figure 24a, 
series connections in Figure 24b. In the series arrangement, water passes through one collector and then 
through the next, increasing the pumping horsepower required to maintain adequate flow, as well as causing 
the downstream collectors to operate at higher, less e fficient temperatures. Parallel connections, in which the 
water is returned directly back to the pool after pa ssing through one collector, are the better choice because 
those difficulties are avoided. 
 
Figure 24 – Collector connections 
The feed and return lines leading to each collector should be approximately the same length. Figure 25a 
illustrates the preferred arrangement, and Figure 25b sh ows a common, but less efficient, connection where 
the flow tends to be short-circuited through the first few collectors and those at the end are starved for flow 
(causing a reduction of their performance). In Figure 25a, the length of the water path is the same for all 
collectors, so the flow is evenly dist ributed. This style of piping will requi re extra pipe, but improved collector 
performance compensates for the additional cost. FDUS 888: 2009 
© UNBS 2009 – All rights reserved  43
 
 
Figure 25 – Flow balancing in collector groups 
Groups of collectors at different heights should be plumbed in such a way they all receive water from the 
lowest point in the system and return it from t he highest point. Figure 26 illustrates a properly plumbed 
system. The dashed line indicates a tempting, but unsatisf actory, arrangement. If the return lines do not come 
from a common height, flow through the panels will be un even, causing a reduction in  performance. Even with 
this piping layout, a balancing valve may be required to  reduce the flow rate in the lower collector(s). 
 
Figure 26 – Plumbing collectors at different heights 
Balancing valves can be used to obtain uniform flow dist ribution in other difficult situations, which occur when 
site requirements make it impractical to balance the flow with simple plumbing arrangements. Balancing 
valves and, if economics permit, flow meters should be installed in the feed line to each group of collectors. 
Starting with all valves completely open, gradually clos e the appropriate valve until the desired flow for each 
group is obtained. An alternative to the use of flow mete rs is to measure the outlet temperature of the various 
collector groups and adjust the balancing valves until these temperatures are within a few degrees of each other. FDUS 888: 2009 
44 © UNBS 2009 – All rights reserved
 Connections between collectors and plumbing pipe ar e commonly made with synthetic rubber couplings, 
which slide over the header and connecting pipe a nd are clamped tightly around each by stainless steel 
bands. To accommodate thermal expansion and misalig nment, these couplings are longer than those used 
between panels. 
A vacuum relief valve may be required on the highest collector group to admit air into the system when the 
pump shuts down and allow the collectors to drain. If nec essary, because of height differences, vacuum relief 
valves can be installed in more than one group of co llectors to facilitate drainage. The vacuum relief valve 
must not admit air into the system during pump oper ation. If it does, the system may be noisy and will 
consume excessive amounts of chemicals due to cons tant bubbling. This means such a valve must be 
installed at a point where the system pressure is above atmospheric pressure. This requires some 
experimentation on systems installed on roofs of multistory buildings. In such cases, the water flowing down the return pipe may cause a vacuum in that pipe. 
Installing the vacuum relief valve on the return e nd of the highest supply header will keep the valve 
pressurized until there is a vacuum caused by draining the supply header. The tilt of the array must allow 
complete drainage. Unfortunately, some pipe layouts w ill not allow gravity drainag e of the collectors. For 
example, in piping over the ridge of a roof, the supply and return are higher then the level of the collectors. 
This prevents proper drainage of the co llectors. Installing a freeze protection valve on the bottom header of 
the collector array may allow gravity to dr ain the panels during freezing conditions. 
9.11   Flow control and safety devices 
One of the most important components in the flow control system is the control (diverter) valve normally 
installed in the main filter flow path after the collect or feed-line and before the collector return (Figure 11b and 
11c). Although this valve can be as simple as a manually  operated ball valve, for convenience, it is generally 
operated automatically. 
Several types of control valves are available. These include  automatic and manual valves. The automatic valves 
include: 
- 3-way duverter or ball valves 
- Bladder-type pinch valves  
- Or specially constructed variations of irrigation valves  
9.11.1  Automatic valves 
Typically, the valves are operated by an electronic differential controller, wh ich measures collector 
temperature and compares it to pool temperature. The high temperature (collector) sensor is mounted in a dull plastic housing that has an absorptivity for solar energy approximating that of the solar panel or in-line on the 
return outlet or pipe near the collector. Since the sensor temperature should simulate the collector 
temperature, it should be mounted alongside a collector  panel and fastened to the same surface to which the 
panels are fastened. All wire connections should be made  secure and watertight, preferably with silicone wire 
connector nuts, heat-shrinkable insulating tubing or as a last resort, durable sealant. 
The lower sensor, which measures pool temperature, sh ould be protected from direct contact with the pool 
water to prevent galvanic corrosion. Most sensors ar e a encapsulated with epoxy into a pipe thread brass 
fitting of 1A" or Vz" MIP, installed in a "well" in  the pipe between the pool and the circulation pump, or 
immersed into the water flow. Many times the sensor can be inserted into the drain port of the pump suction 
basket. It is important to ensure the "cold" sensor regi sters the temperature of t he pool water not the ambient 
air or warmth from sunshine on the sensor capsule. 
The electronic controller itself requires electrical power. Sometimes it can be connected in parallel with the pool pump or timer, but since 120V or 240V electricity is  involved installers should consult their local building 
officials to find out if an electrician is required to  make the connection. Approved conduit should be used for 
this wire. FDUS 888: 2009 
© UNBS 2009 – All rights reserved  45
 In the installation of the automatic 3-way actuator and controller, the low voltage output from the controller 
powers the motor and turns the valve. It is important to ensure proper alignm ent of the motor, directional flow 
and direction of diverted flow. Be careful not to actuat e the valve and stop flow from  the filter. Pressures in 
excess of the filter's maximum operating pressure could damage the filter. 
Normal operation is flow to the pool from the filt er. When the signal from the high temperature sensor 
indicates heat collection is available at the collectors, the controller activates the valve and diverts the flow 
from the pool to the collectors. 
In the installation of a pinch valve control system, it is necessary to connect two pressure lines between the 
pool pump and the control box. Small-diameter (1/8-inch)  plastic lines are generally used. Since most pool 
pumps have a 1/4-inch, threaded pipe plug in the side of  the strainer housing (near the bottom), the low-
pressure line is usually attached to an adapter at that point. The high-pressure line should be tapped into the 
pipe on the discharge side of the pump. 
When the high temperature sensor registers the collect ors are warmer than the pool water, the electronic 
control opens the line from the discharge side of the pump and inflates the bladder in the pinch valve. This 
diverts flow through the solar system . When the high temperature sensor sign als the collectors are cooler than 
the pool water, the line from the suction side of th e pump is opened, forcefully deflating the bladder and 
allowing flow to bypass the collectors. 
Another possible control valve, the irrigation style, achieves the same results but operates in a slightly 
different fashion. It is plumbed into the system by standa rd piping procedures. A small suction line is tapped 
into the pump inlet strainer housing, but in this case, the suction line is connected to the valve body itself. A 
pressure line is not used. A low voltage wire also connects a small solenoid valve mounted on the valve body 
to the control box. Most irrigation ty pe valves will increase the pressure  and reduce the flow rate of the 
system. 
The system control compares collector  temperature with pool temperature as before. If solar heat is available, 
an electrical signal causes the solenoid valve to open the suction line. This suction closes the main valve 
diaphragm, diverting flow through the collectors. When solar energy is not available, the solenoid valve 
remains closed, the main valve diaphragm (which is spri ng loaded) opens, and the flow bypasses the collector 
array. (In another version the spring loading keeps the main valve diaphragm closed and the solenoid induces 
its opening.) 
9.11.2  Manual valves 
Manual valves can be two- or three-way ball valves or st andard flow diverter valves. Operation of these valves 
is completely manual and includes isolating the flow to  the pool by diverting flow to the collectors. It is 
important that the isolation valve to the pool is betw een the collector supply and return lines in the system 
piping design. 
9.11.3  Activating the system 
After installation is completed, it is necessary to activate and test the system for proper operation. A few of the most important checks are discussed here. 
9.11.3.1 Purging the system 
Bits of plastic from rough pipe cuts, sand and other debris should be flushed from the system to avoid 
clogging small fluid passages in the collectors. Pu rging can be accomplished by leaving one or two 
strategically placed joints open. The circulation pump can be briefly turned on to flush water through the 
system, and then final connections can be made. Small amounts of pool water can be discharged onto grass 
or sand, but large volumes should be piped to safe drains. 
9.11.3.2  Pressure testing 
The entire system should be pressurized to the maximum operating pressure. This can be accomplished in a 
number of ways. FDUS 888: 2009 
46 © UNBS 2009 – All rights reserved
 If piping passes through critical areas, such as an attic or public area, which is not recommended, a 
continuous run of piping is recommen ded. Avoid couplings and fittings in  areas where a leak could cause 
significant damage. The system should be pressurized with an air compressor and tested for leaks. Testing 
the pipe to twice the operating pressure is recommended, but be sure not to exceed t he pressure rating of the 
pipe. Leaks can be located readily by lis tening for the hiss of escaping air. 
Installations where all piping is ro uted through areas where a temporary leak will do no harm may be pressure 
tested by turning on the circulating pumps. The appropriate  valves in the circulation system should be closed 
to produce the highest possible pressures in the new piping. Be sure to have someone standing by; ready to 
turn the pump off in the event a leak is discovered. 
During the pressure check, every conne ction should be visually inspected and shaken to ensure that it is well 
made. 
9.11.3.3  Testing control devices 
Automatic control devices should be checked for proper operation. Consult the manuf acturer's specifications 
for the controls being used and determine the possible operating modes. Test in all of these modes and make 
a permanent record of the results. Checking control operat ion immediately after installation can prevent costly 
callbacks later. 
9.11.3.4  Testing flow rates 
Proper flow through the collector array and filtration system  is required. Inexpensive flow meters are available 
and should be used to confirm desired rates have been ac hieved. As previously mentioned, turnover time 
must not be increased above an acceptable level. 
9.11.3.5  Testing temperature rises 
The temperature difference between the feed line to the solar system and the warmer return line should be 
checked. Remember, the temperature rise on even a su nny day should be quite modest, approximately 5- 
10°F, for low-temperature collectors. Thermometers inst alled in these lines can be used to make accurate 
readings. 
If the temperature rise is too large, it indicates not enough water is passing through the collectors. Check the system thoroughly and correct the problem because collec tor efficiency drops dramatically as the operating 
temperature rises. It sounds strange to the homeowner but lots of water being warmed slightly provides more 
heat than a little water being warmed a lot. 
9.12    Instructing the homeowner 
There are several important reasons to spend a few minutes instructing the ho meowner on the operation of 
the new solar pool heater. First, it will enable the owner to  ascertain whether the syst em is operating and thus 
reduce "false alarm" call-backs. Second, it will enable the owner to explain the new unit to friends and neighbours. Third, it will equip the owner to make minor adjustments and reduce service calls for the installer.  
Explain the operation of all valves and controls and how the water circulates in the various modes. Spend a 
little time on the automatic control so that the owner can make seasonal or other adjustments that may be 
required. Provide the owner with the system manual. 
It is very important to explain the amount of energ y being delivered to the pool is the product of the 
temperature rise and the flow rate. High temperature ri ses feel impressive, but they cause the collectors to 
operate inefficiently and deliver less he at to the pool. Sometimes this point is difficult to make, so you may 
have to explain it in several different ways. FDUS 888: 2009 
© UNBS 2009 – All rights reserved  47
 10.   Commissioning, handover and documentation 
10.1    General 
The person responsible for commissioning of the comp leted system should check that all aspects of the 
installation have been executed in accordance wi th the designer's and the component manufacturer's 
instructions. 
10.2   Commissioning of direct circulation systems 
The following procedures should be carried out. 
a)  The free movement of all valves and pump impelle rs should be checked manually  where this is possible 
without dismantling. 
b)  For systems integrated with t he filtration circuit, the solar equipment should be shut off with valves and 
the filtration circuit checked for correct operation, and all pressure gauges, where fitted, should read 
within manufacturer's/designer's limits. Any defects should be remedied before proceeding. 
c)  Using manual or motorized valves, as appropriate,  water should be diverted through the solar collectors. 
It may be necessary to override the solar system c ontroller to effect this diversion under unfavourable 
weather conditions. Alternatively, the collector sensor may be gently heated, thus qualitatively checking 
the operation of the c ontrol system also. 
d)  All pipework should be checked for leaks. Correct operation of air vents shoul d be confirmed. If it is 
desired to prevent air entrainment owing to negative pressure within the system a regulating valve on the 
delivery side of the solar collectors, may be partly cl osed. It should be ensured however that this action 
does not reduce the system flow rate below that re commended by either filtration equipment or solar 
collector suppliers. 
e)  The flow rate through the solar collectors should be assessed, where possible with a flow meter. It should 
be confirmed that there is no significant imbalance of  flow between individual collectors. The designer's 
recommendations should be followed with regard to adjus tment of regulating valves if fitted. The flow is 
balanced if each collector's outlet temperature is si milar. If unglazed collectors are fitted their entire 
surface should feel cool while exposed to bright sunshine. 
f)  If the system has been designed to be automatically  self draining this function should be checked [see 
6.2.2 5)]. 
10.3    Commissioning of indirect circulation systems 
The following procedures should be carried out. 
a)  The free movement of all valves and pump impelle rs should be checked manually  where this is possible 
without dismantling. 
b)  For systems integrated with t he filtration circuit it should be check ed that the filtration circuit operates 
correctly, and that all pressure gauges, where fitted, should read within manufacturer's/designer's limits . 
Any defects should be remedied/reported before proceeding. 
c)  Indirect systems in which water or water based flui d is the heat transfer fluid should be thoroughly flushed 
out with water and tested to ensure that there are no leaks prior to being drained and refilled (see 10.4). 
When using proprietary heat transfer fluids the manufacturer's instructions should be followed with regard 
to flushing out the pipework, testing for leaks and filling with the fluid. 
d)  It is most important to purge sealed or permanently filled systems of all air and this operation should be 
carried out at the time of installation by means of appropriately positioned air vents. The best method of 
achieving air release is to switch the circulating pump on and off a number of times while venting the FDUS 888: 2009 
48 © UNBS 2009 – All rights reserved
 system. This operation should preferably be carried out in sunny conditions in order to ensure the release 
of dissolved air. Failure to purge the air fully may necessitate a call back visit. On sealed systems it may 
sometimes be necessary to re-establish t he cold filled pressure and fluid volume. 
e)  If the system is designed to fill and drain automatica lly to achieve frost or boiling protection, the correct 
functioning of the system or equipment should be check ed in accordance with the designer's instructions. 
f)  The flow rate through the solar collectors should be assessed and it should be confirmed that there is no 
significant imbalance of flow between individual collectors [see 10.2 e)]. 
g)  If the system has been designed to be automatically  self-draining this function should be checked. 
10.4   Precautions when pressure testing sealed circuits 
Care should be exercised when carrying out pressu re tests on completed solar heating systems and a 
pressure relief valve should always be fitted to protect components. If the completed circuit is to be filled with 
water under pressure to check for leaks, it is recomm ended that such a test is carried out either with the 
collectors covered or during hours of darkness in order to avoid: 
a)  the possibility of substantial te mperature fluctuation with in the collectors produc ing sufficient pressure 
changes to give false test readings; 
b)  the possibility of the heat transfer fluid boiling under test. 
10.5    Making good 
Before an installation can be regarded as being satisfactorily completed the installer has to ensure that any damage caused by the fitting of any part of the system, e.g. the solar collect ors, pipes or fixing brackets, is 
restored and made good. Pipework insulation, where spec ified in the system design (see 6.4.1) should be 
completed at this time. 
In this connection particular attention should be paid to repairing and sealing any damage to the roof lining. Damage to guttering, walls, garden and lawn, by ladders,  scaffolding, hoists or other equipment should also 
be made good. 
10.6    Handover and documentation 
At the time of handover the client should be provided with an appropriate do cument certifying that the system 
has been installed and commissioned satisfactorily. If for any reason it is not possible to complete commissioning, arrangements should be made for this to be completed at a later date. 
If the operation of the solar heating system is dependent upon the operation of the filtration pump it should be 
ensured, in conjunction with the pool ow ner/operator, that it is set correctly  so that the pump will run at least 
during daylight hours. The system should be handed over either in a fully operational state or 
decommissioned to an extent appropriate to the time of year and system's design. 
An owner's documentation wallet should be handed over containing the following items. 
a)  The handover document. 
b)  A user's data sheet (see 10.7). 
c)  Warranties or guarantees issued by the manufac turers of the components or by the installer. 
d)  Operating and maintenance instructions describing start-up, normal running and shut-down procedures in 
a form readily intelligible to the non-technical us er. These should also include details of protection 
provided against frost and overheating if applicable. Deta ils of action to be taken in the event of apparent 
faults should be provided. FDUS 888: 2009 
© UNBS 2009 – All rights reserved  49
 e)  A circuit diagram of any electrical controls. 
If special additives are used in the heat transfer fluid of indirect circuits, durable i dentifying labels providing the 
necessary information as to the formulation, soluti on strength and specific hazard, source of supply and 
expected life of the liquid should be attached to the a ppropriate system component in a conspicuous manner 
for future reference. 
A separate label should also record the date of the installation and the name and address of the installer. 
10.7   User's data sheet 
A list of major components should be provided indicating the number, model and make of items of equipment 
that have been installed. As a minimum the solar coll ectors, control system components and pumps should be 
included in the list. 
The circuit design should be identified as direct or indirect  and in the case of the latter, full details of the heat 
transfer fluid and the means of accomm odating fluid expansion should be given. 
The method of frost protection should be stated and a cl ear, bold indication of any need to drain the system 
manually to provide frost protection should be included together with instructions for draining. 
The method of system control should be stated together with any facility for overriding the automatic control 
system. 
Data regarding the need for and frequency of maintenance should be given. Any servicing requirements 
should also be stated. 
It is also recommended that the client's attention should be dr awn to the fact that it is  prudent to check that the 
solar heating system is included on an existing insura nce policy or that alternative insurance arrangements 
are made. 
Any special hazards to be avoided should be listed, for example, the high temperature which may be attained 
by collectors when the fluid flow is interrupted. 
 
 
 
 
 
 
 
 
 
 
 
 FDUS 888: 2009 
50 © UNBS 2009 – All rights reserved
 Annex A 
 
Details of the model system referred to  in clause 6 for thermal performance 
A.1  Model system  
The figures heat transferred to the pool quoted in clause  6 are based on computer simulations. Details of the 
computer model used are as follows. 
Item Description 
Collector orientation South facing and titled at 45o from horizontal. 
NOTE      Details of the collectors modelled are given in A.2 
Pool temperature The pool is assumed to be fully mixed and maintained at a fixed temperature by an 
auxiliary heating source. 
Pool water is circulated directly through the collectors and the inlet water 
temperature to the collectors is equal to the pool water temperature. 
Collector to pool loop Pumped circulation at fixed flow rate, using the pool water as the heat exchange 
fluid, having a specific heat capacity of 4.184 kJ/(kg K). 
Circulation switched on and off at fixed values of temperature differential between inlet and outlet of the collector. 
Insulation Heat losses from pipe work are assumed to be zero. 
Weather data Hourly data as prov ided by the Meteorological office for Kew from 1959 to 1979 
inclusive. 
A.2  Solar collector characteristics 
Methods of test for evaluating the thermal performance of solar collectors are given in US 854-2. Calculations 
have been carried out using quantities which are considered  likely to characterize properly constructed solar 
collectors of certain commonly-used types. 
Two parameters, and U, are used to characterize the collectors. In the nomenclature used in the book Solar 
energy thermal processes (J A Duffie and W A Beckman, Wiley, New York, 1975) these may be identified with 
the quantities F’ (ατ)0 and F’U L respectively, where ( ατ)0 is the product of the abs orptance of the absorber 
plate surface and the solar radiation transmittance of the cover, if present, at normal incidence; UL is the 
overall heat loss coefficient and F’ is the collector plate efficiency factor. 
Typical values of η0 and U are selected to represent the characterist ics of single-glazed selective insulated 
collectors, single-glazed matt black insulated collectors, and unglazed uninsulated collectors, given in Table 2. 
These figures are derived from results of tests on numerous collectors by the Energy Equipment Testing 
Service at University College Card iff, in accordance with BS 6757. The unglazed collectors were tested 
resting on a backing plate. 
Table 2 – Typical values of rf0 and U for different types of collector 
Collector type η0 U  (W/(m2.K) 
1.Single-glazed selective 
2.  Single-glazed matt black 
3.  Unglazed 0.7 
0.7 
0.8 5.3 
7.7 
20 
A.3  Other assumptions 
For all three types of collector it is  assumed that the albedo of the surroundings is 0.2 and the incidence-angle 
modifiers for beam radiation ( lb) and diffuse radiation ( ld) are as follows: FDUS 888: 2009 
© UNBS 2009 – All rights reserved  51
 - for beam radiation lb = 1.1 — (0.1/cos Z)  
(where Z is the incidence angle) 
-  for diffuse radiation ld = 0.9 
Factors that are assumed to be different for the various collectors are as follows: 
Collector type (see Table 2)       1    2     3 
Fluid flow rate [kg/(m2 s)]       0.02    0.02   0.04 
Temperature differential on K       2      2    0.5 
Temperature differential off K      0.5    0.5      0 
Heat removal factor FR       0.969   0.955   0.929 
NOTE  The temperature differentials used in the model are the assumed fluid tem perature differences rather than those 
which operate the contro l system (see 5.3.3). 
A.4    Collector output 
The collector energy output, or heat delivered to the pool per unit area of collector, in a given hour is 
determined by: 
Q = F[η0 (lbHb + ldHd) - 3600 U (Tp - Ta)] 
where 
Q   is the hourly output (in J/m2); 
F   is the heat-removal factor/plate efficiency factor = FR/F'; 
η0   is the zero heat-loss efficiency; 
lb   is the incidence-angle modifier for beam radiation; 
ld   is the incidence-angle modifier for diffuse radiation; 
Hb   is the hourly beam irradiation (in J/m2); 
Hd  is the hourly diffuse irradiation (in J/m2); 
U   is the collector heat loss coefficient [in W/(m2-K)]; 
TL   is the pool temperature (in °C); 
Ta   is the air temperature (in °C). 
The output given by the above equatio n has been determined for every hour of the 21-year period 1959 to 
1979 at Kew. From this, the average total energy output  for the whole year, for the period May to September 
inclusive, and for the month of July is given respectively in Figure 4 to Figure 6. 
Data for each of the separate months of the year are given in Figure 27 and Figure 28. 
 
 
 
 
 
 
 
 FDUS 888: 2009 
52 © UNBS 2009 – All rights reserved
 
 
NOTE   The performance of collectors, particularly those of  type 3, will depend on many factors and these curves should be 
interpreted with reference to Clause 7. 
Figure 27 — Average energy output from collectors for May, June, July, August and September  FDUS 888: 2009 
© UNBS 2009 – All rights reserved  53
 
 
 
NOTE  The performance of collectors, particularly those of type 3, will depend on many factors and these curves should be 
interpreted with reference to Clause 6. 
Figure 28 — Average energy output from collectors for October, November, December, January, 
February, March and April  
 FDUS 888: 2009 
54 © UNBS 2009 – All rights reserved
 Bibliography 
 [1] BS 417-2, Specification for galvanized low carbon steel cisterns, cistern lids, tanks and cylinders — 
Part 2: Metric units 
[2] BS 864-2, Capillary and compression tube fittings of cop per and copper alloy — Pa rt 2: Specification 
for capillary and compression fittings for copper tubes 
[3] BS 864-3, Capillary and compression tube fittings of copper and copper alloy — Part 3: Compression 
fittings for polyethylene pipes 
[4] BS 1565-2, Galvanized mild steel indirect cylinders, annul ar or saddle-back type — Part 2: Metric 
units 
[5] BS 1566-1, Copper indirect cylinders for domestic purposes  — Part 1: Specification for double feed 
indirect cylinders  
[6] BS 1566-2, Copper indirect cylinders for domestic purposes — Part 2: Specification for single feed 
indirect cylinders 
[7] BS EN 1057, Copper and copper alloys — Seamless, round copper tubes for water and gas in 
sanitary and heating applications 
[8]  BS 3198, Specification for copper hot water storag e combination units for domestic purposes 
[9]  BS 4072, Wood preservation by means of water-borne copper/chromium/arsenic compositions 
[10] BS 4213:2004, Cisterns for domestic use — Cold water storage and combined feed and expansion 
(thermoplastic) cisterns up to 500 L — Specification 
[11] BS 4814, Specification for expansion vessels using an internal diaphragm, for sealed hot water 
heating systems 
[12]  BS EN 12288, Industrial valves — Copper alloy gate valves 
[13] CISPR 14-1, Electromagnetic compatibility — Requirement s for household appliances, electric tools 
and similar apparatus — Part 1: Emission 
[14] CISPR 14-2, Electromagnetic compatibility — Requirement s for household appliances, electric tools 
and similar apparatus — Part 2: Immunity — Product family standard 
[15]  ISO 559:1991, Steel tubes for water and sewage 
[16]  ISO 12468-1:2003, External exposure of roofs to fire — Part 1: Test method 
[17]  ISO 12468-2:2005, External fire exposure to roofs — Part 2: Classification of roofs 
[18]  ISO 3008:2007, Fire-resistance tests — Door and shutter assemblies 
[19] ISO 22391-1:2007, Plastics piping systems for hot and cold water installations — Polyethylene of 
raised temperature resistance (PE-RT) — Part 1: General 
[20] ISO 22391-5:2007, Plastics piping systems for hot and cold water installations — Polyethylene of 
raised temperature resistance (PE-RT) — Pa rt 5: Fitness for purpose of the system 
[21] ISO 4422-1:1996, Pipes and fittings made of unplasticized poly(vinyl chloride) (PVC-U) for water 
supply —Specifications  — Part 1: General FDUS 888: 2009 
© UNBS 2009 – All rights reserved  55
 [22] ISO 4422-2:1996, Pipes and fittings made of unplasticized poly(vinyl chloride) (PVC-U) for water 
supply —Specifications — Part 2: Pipes (with or without integral sockets) 
[23] ISO 4422-3:1996, Pipes and fittings made of unplasticized poly(vinyl chloride) (PVC-U) for water 
supply —Specifications — Part 3: Fittings and joints 
[24] ISO 4422-4:1997, Pipes and fittings made of unplasticized poly(vinyl chloride) (PVC-U) for water 
supply —Specifications — Part 4: Valves and ancillary equipment 
[25] ISO 4422-5:1997, Pipes and fittings made of unplasticized poly(vinyl chloride) (PVC-U) for water 
supply —Specifications — Part 5: Fitness for purpose of the system 
[26] ISO 727-1:2002, Fittings made from unplasticized poly(vinyl chloride) (PVC-U), chlorinated poly(vinyl 
chloride) (PVC-C) or acrylonitrile/butadiene/styrene (ABS) with plain sockets fo r pipes under 
pressure — Part 1: Metric series 
[27] ISO 22897:2003, Glass in building — Glazing and airborne sound insulation — Product descriptions 
and determination of properties 
[28] ISO 16932:2007, Glass in building — Destructive-windstorm-resistant security glazing — Test and 
classification 
[30] ISO 3934:2002, Rubber, vulcanized and thermoplastic — Preformed gaskets used in buildings —
Classification, specifications and test methods 
[31] ISO 9050:2003, Glass in building — Determination of light tr ansmittance, solar direct transmittance, 
total solar energy transmittance, ultraviole t transmittance and related glazing factors 
[32] ISO 8873-1:2006, Rigid cellular plastics — Spray-applied polyurethane foam for thermal insulation — 
Part 1:Material specifications 
[33] ISO 8873-2:2007, Rigid cellular plastics — Spray-applied polyurethane foam for thermal insulation — 
Part 2: Application 
[34] ISO 24510, Activities relating to drinking water and wastewater services — Guidelines for the 
assessment and for the improvement  of the service to users 
[35] ISO 24512, Activities relating to drinking water and wastewater services — Guidelines for the 
management of drinking water utilities and for the assessment of drinking water services 
[36]  ISO 2103:1986, Loads due to use and occupancy in residential and public buildings 
[37]  ISO 4354, Wind actions on structures 
[38]  ISO 12494, Atmospheric icing of structures 
[40]  ISO 9453, Soft solder alloys — Chemical compositions and forms 
[41] ISO 9454-1, Soft soldering fluxes — Classification and requirements — Part 1: Classification, 
labelling and packaging 
[42] ISO 9454-2:1998, Soft soldering fluxes — Classification and requirements — Part 2: Performance 
requirements 
[43] ISO 12224-1, Solder wire, solid and flux cored — Specification and test methods — Part 1: 
Classification and performance requirements 
 FDUS 888: 2009 
56 © UNBS 2009 – All rights reserved
 [44]  ISO 4952:2006, Structural steels with improved atmospheric corrosion resistance 
[45] ISO 11303:2002, Corrosion of metals and alloys — Guidelines for selection of protection methods 
against atmospheric corrosion 
[46]  ISO 11972:1998, Corrosion-resistant cast steels for general applications 
[47] KS 1855-1:2008, Thermal solar systems and components — Custom built systems — Part 3: 
General requirements 
[48] KS 1855-2:2008, Thermal solar systems and components — Custom built systems —Part 2: Test 
methods 
[49] KS 1855-3:2008, Thermal solar systems and components — Custom built systems —Part 3: 
Performance characterization of st ores for solar heating systems 
[50] KS 1869, Standard test method for determination of solar reflectance near ambient temperature 
using a portable solar reflectometer 
[51] KS 1869, Standard test method for determination of solar reflectance near ambient temperature 
using a portable solar reflectometer 
[52]  KS 1870:2008, Standard specification for rubber seals us ed in flat-plate solar collectors  
[53] KS 1871:2008, Standard practice for determining resistance of solar collector covers to hail by 
impact with propelled ice balls 
[54] KS 1891, Standard practice for evaluating absorptive solar receiver materials when exposed to 
conditions simulating stagnation in solar collectors with cover plates 
[55]  KS 1892, Standard practice for evaluating solar absorptive materials for thermal applications 
 
 
 
 
 
 
 
 
 
 
 
 
 FDUS 888: 2009 
© UNBS 2009– All rights reserved 
 Certification marking 
Products that conform to Uganda standards may be  marked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below.  
The use of the UNBS Certification Mark is gove rned by the Standards Act, and the Regulations made 
thereunder. This mark can be used only by those licens ed under the certification mark scheme operated by 
the Uganda National Bureau of Standards and in co njunction with the relevant Uganda Standard. The 
presence of this mark on a product or in relation to a product is an assurance that the goods comply with the 
requirements of that standard under a system of supervision, control and  testing in accordance with the 
certification mark scheme of the Uganda National  Bureau of Standards. UNBS marked products are 
continually checked by UNBS for conformity to that standard.  
Further particulars of the terms and conditions of  licensing may be obtained from the Director, Uganda 
National Bureau of Standards.  
 
 FDUS 885: 2009 
 
ICS 27.160 
Price based on nn pages 
© UNBS 2009– All rights reserved