DRAFT UGANDA STANDARD  
  DUS 1560  
First Edition  
2013-09-24  
 
 
 Refer ence number 
DUS 1560: 2013 
© UNBS 2013  
  
Rotational moulded polyethylene water 
storage tanks — Specification 
 
 DUS 1560 : 2013 
© UNBS 2013 – All rights reserved  ii
 Compliance with this standard does not, of itself c onfer immunity from legal obligations 
A Uganda Standard does not purport to include all n ecessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS 2013 
All rights reserved. Unless otherwise specified, no  part of this publication may be reproduced or util ised in any 
form or by any means, electronic or mechanical, inc luding photocopying and microfilm, without prior wr itten 
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 41 505 995 
Fax: 256 41 286 123 
E-mail: unbs@unbs.go.ug  DUS 1560 : 2013 
© UNBS 2013 – All rights reserved  iii
 Contents Page  
Foreword .......................................... ................................................... ................................................... ...... iviviv  
1 Scope ............................................. ................................................... .................................................. 111 
2 Normative references .............................. ................................................... ....................................... 111 
3 Terms and definitions ............................. ................................................... ....................................... 111 
4 Requirements ...................................... ................................................... ............................................ 444 
4.1  General ........................................... ................................................... ................................................. 444 
4.1  Materials ......................................... ................................................... ................................................. 444 
4.2  Carbon black content .............................. ................................................... ....................................... 555 
4.3  Catalyst .......................................... ................................................... .................................................. 555 
4.4  Fillers and pigments .............................. ................................................... ......................................... 555 
4.5  Types ............................................. ................................................... .................................................. 555 
4.6  Fittings .......................................... ................................................... ...................................................  555 
4.7  Sizes.............................................. ................................................... ...................................................  666 
4.8  Net capacity (actual).............................. ................................................... ......................................... 666 
4.9  Design Requirements................................ ................................................... ..................................... 666 
4.9.1  Cylinder Shell (Unsupported Portion of Tanks) ..... ................................................... ..................... 666 
4.9.2  Cylinder Shell (Externally Supported Tanks) ....... ................................................... ....................... 666 
4.9.3  Top Head .......................................... ................................................... ............................................... 666 
4.9.4  Bottom Head ....................................... ................................................... ............................................ 777 
4.9.5  Open-Top Tanks .................................... ................................................... ......................................... 777 
4.10.  Dimensions and Tolerances ......................... ................................................... ................................. 777 
5 Quality of finish ................................. ................................................... ............................................. 888 
6 Test methods ...................................... ................................................... ............................................ 888 
6.1  Resistance to deformation test .................... ................................................... ................................. 888 
6.2  Tensile strength test ............................. ................................................... ......................................... 888 
6.3  Flexural strength ................................. ................................................... ........................................... 888 
6.4  Hydrostatic pressure head test .................... ................................................... ................................. 888 
7 Sampling .......................................... ................................................... ............................................... 999 
7.1  Lot ............................................... ................................................... ................................................... .. 999 
8  Marking ........................................... ................................................... ................................................. 999 
9  Shipping .......................................... ................................................... .......................................... 101010  
10  Workmanship ....................................... ................................................... ..................................... 101010  
Annex A (normative)  Carbon black content ......... ................................................... ............................. 111111  
Annex B (Normative) ............................... ................................................... .............................................. 131313  
Annex C (Normative) ............................... ................................................... .............................................. 141414  
Annex D (Normative) Deformation test .............. ................................................... ................................. 151515  
Bibliography ...................................... ................................................... ................................................... .. 232323  
 DUS 1560 : 2013 
© UNBS 2013 – All rights reserved  iv
 Foreword 
Uganda National Bureau of Standards (UNBS) is a par astatal under the Ministry of Trade, Industry and C o-
operatives established by the Act of Parliament of 1983, of the Laws of Uganda.  UNBS is mandated to c o-
ordinate the elaboration of standards and is  
(a) a member of International Organisation for Stan dardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex Alimentar ius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT/SPS Agreement s of the World Trade Organisation (WTO). 
The work of preparing Uganda Standards is carried o ut through Technical Committees. A Technical 
Committee is established to deliberate on standards  in a given field or area and consists of represent atives of 
consumers, traders, academicians, manufacturers, go vernment and other stakeholders. 
Draft Uganda Standards adopted by the Technical Com mittee are widely circulated to stakeholders and th e 
general public for comments. The committee reviews the comments before recommending the draft standard s 
for approval and declaration as Uganda Standards by  the National Standards Council.  
Committee membership 
Crestanks Limited 
EBOWA Investments Limited 
E-WEL International Consult LTD 
Kyambogo University 
Makerere University 
Roofings Limited 
Steel and Tubes Limited 
Uganda Baati Limited 
Uganda National Bureau of Standards 
 UGANDA STANDARD DUS 1560: 2013 
 
© UNBS 2013 – All rights reserved  1
 Rotational moulded polyethylene water storage tank—
specification 
1 Scope 
This draft Uganda Standard specifies the requiremen ts and methods of tests for rotational moulded 
polyethylene water storage tanks (closed and open t op tank). 
This standard is not applicable to underground tank s. 
The standard does not cover mobile water tanks and horizontal cylindrical water tanks. 
2 Normative references 
The following referenced documents are indispensabl e for the application of this document. For dated 
references, only the edition cited applies. For und ated references, the latest edition of the referenc ed 
document (including any amendments) applies. 
ISO 1209-1 : Rigid cellular plastics — Determination of flexur al properties — Part 1: Basic bending 
test 
ISO 1209-2: Rigid cellular plastics — Determination of flexural  properties — 
Part 2: Determination of flexural strength and appa rent flexural modulus of elasticity 
3 Terms and definitions 
For the purposes of this standard, the following terms and definitions shall apply  
3.1 
net capacity (actual) 
net total volume of water contained between the low est level of the overflow and lowest level of  outlet (see 
Figures 1 and 2) DUS 1560: 2013 
© UNBS 2013– All rights reserved  2
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Key 
RCC – Reinforcement  
PCC - Pre-cast cement concrete 
Note: 
The requirements for the construction of the reinfo rced cement concrete or pre-cast cement concrete de pend on the 
capacity of the tank and location 
Civil engineering will establish the viability of t he geology that the water tank will be placed on an d this will dictate site 
preparation and cost 
The choice of materials of construction will be imp acted by the whether the tank is located indoors, o utdoors or 
underground. 
Figure 1 — Typical perspective view of closed top t ank 
DUS 1560: 2013 
© UNBS 2013– All rights reserved  3
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 2: Typical view of open top tank 
3.2 
gross capacity (nominal) 
the total enclosed volume of the tank including any  space, which may not be capable of being filled  with 
water 
3.3 
mould parting 
a circumferential line visible only on the external  surface of the tank corresponding to a parting joi nt  of the 
mould required for rotational moulding (see Figures  1 and 2) 
3.4 
overall height 
the height of the finished empty tank at its highes t point, including the top rim of the manhole and l id  of the 
tank (see Figures 1 and 2) 
3.5 
effective height 
the height of the finished empty tank from its base  to the point where overflow connection is  provided for the 
purpose of limiting water storage capacity (see Fig ures 1 and 2) 
3.6 
overall diameter 
the maximum outer diameter of finished empty tank m easured at its base (see Figures 1and 2) 
3.7 
man-hole/hand-hole 
a hole of suitable internal diameter provided at th e top of the tank for the purpose of inspection of  internal 
surface and entry into the tank (see Figure 1) 
DUS 1560: 2013 
© UNBS 2013– All rights reserved  4
 3.8 
internal diameter of man-hole/hand-hole 
the internal diameter of the rim of the manhole mea sured as the mean of two perpendicular  diameters (see 
Figures 1 and 2) 
3.9 
closed tank 
see Figure 1 
3.10 
open top tank 
see Figure 2 
3.11 
rotational molding 
a three-stage commercial process consisting of load ing the mold with powdered resin, fusing the 
resin by heating while rotating the mold about more  than one axis, and cooling and removing the 
molded article 
4 Requirements 
 
4.1 General 
The following two condition apply to both open-topp ed and closed-topped water storage tanks:: 
a) own hydrostatic head of water; and 
b) uniform flat base support. 
The nominal service temperature is 1 ° C to 50 ° C. 
 
4.1 Materials 
4.1.1  The materials for construction of the tank and lid  that come into contact with water shall be of 
food grade.  
4.1.2  Water tanks meant for outdoor use shall be manufac tured from virgin polyethylene materials 
intended for the rotational molding process (resin) . The outer layer of the tank, however, shall be 
made from virgin and 10 — 20 % reusable material.  
4.1.3  All polyethylene resin material shall contain a mi nimum of a U.V. 8 stabilizer as compounded 
by the resin manufacturer.  
4.1.1 The material for construction of the tank and lid, which comes into contact with water, shall 
not impart any taste, colour or odour to water; the y shall neither have any toxic effect nor 
contaminate water thereby making it unpotable.  
4.1.5  The life span for the tank shall not be less than 15 years.  DUS 1560: 2013 
© UNBS 2013– All rights reserved  5
 4.2 Carbon black content 
4.2.1  Carbon black pigment shall be added, for tanks int ended to be used outdoor, to the moulding 
material for the outer layer or the exposed layer a nd shall be not less than 2.5 ± 0.5 % when tested 
in accordance with Annex A.  
4.2.2  The carbon black or any other pigment added shall be uniformly dispersed in the material, 
when tested in accordance with Annex B.  
4.3  Catalyst 
The total amount of inorganic present in polyethyle ne shall not exceed 0.2 % (m/m) when tested by 
atomic absorption method and in accordance with Ann ex C. An alternative method of testing for the 
metals shall be by x-ray fluorescence, where the at omic absorption method may not be applicable 
or just non-operational. 
4.4 Fillers and pigments 
The plastic shall not contain any filler. Pigments may be added as desired by the customer, or as 
designated by polymer processing companies, but sha ll not exceed 0.5% dry blended, and 2% 
compounded in, of the total weight. 
4.5 Types 
There shall be two types of tanks vis-a-vis: 
a) cylindrical vertical tanks (closed and open-end) ; and 
b) rectangular loft tanks (see Figure 3 a), and b).  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 3 a): Cylindrical vertical closed top tank F igure 3 b) Rectangular loft tank  
4.6 Fittings 
It shall be the prerogative of the manufacturer to provide as much information as is possible to the 
consumer regarding fittings. 
DUS 1560: 2013 
© UNBS 2013– All rights reserved  6
 4.7 Sizes 
Tank sizes will vary in accordance with the custome r's requirements. 
4.8 Net capacity (actual) 
When filled to the lowest level of overflow, and th e volume attained measured, tanks shall discharge 
the capacity marked on it. 
4.9  Design Requirements 
4.9.1 Cylinder Shell (Unsupported Portion of Tanks)  
The minimum required wall thickness of the cylindri cal shell at any fluid level for tanks of 1000-L 
capacity shall be determined by the following equat ion, but shall not be less than 4.7 mm thick and 
the tolerance indicated in 4.10.3 applies to these dimensions. 
2SD OD H SG 0.433 
2SD OD PT ×× × = × = 
Where; 
 
T = wall thickness, mm, 
P = pressure, MPa 
SG = specific gravity of fluid, g/cm 3 
H = fluid head, m, 
OD = outside diameter of tank, mm, and  
SD = hydrostatic design stress, MPa. 
The standard design specific gravity shall be 1.5 o r 1.9. 
4.9.1.1 The hydrostatic design stress that is used to deter mine the minimum wall thickness at any 
fluid level must be based on hoop stress data for t he polyethylene materials. The hydrostatic 
design-basis must be reduced by a service factor to  determine the actual hydrostatic design stress. 
The maximum service factor shall be 0.5 for wall th icknesses less than 9.5 mm. For thicknesses 
equal to or greater than 9.5 mm, the maximum servic e factor shall be 0.475.  
4.9.1.2  Tank hoop stresses shall be derated for service ab ove 23° C.  
4.9.2 Cylinder Shell (Externally Supported Tanks) 
The minimum required wall thickness for the cylinde r straight shell must be sufficient to support its 
own weight in an upright position without any exter nal support, but shall not be less than 4.7 mm 
thick. The tolerance indicated in 4.10.3 applies to  these dimensions. 
4.9.3 Top Head 
Must be integrally molded with the cylinder shell. The minimum thickness of the top head shall be 
equal to the top of the straight wall. DUS 1560: 2013 
© UNBS 2013– All rights reserved  7
 4.9.4 Bottom Head 
Must be integrally molded with the cylinder shell. The minimum thickness for a full-supported flat-
bottom head shall be 4.7 mm. The radius of the bott om knuckle of a flat-bottom tank shall not be 
less than 25.4 mm for tanks with a diameter less th an 1.8 m and 38.1 mm for a diameter greater 
than 1.8 m . The minimum thickness of the radius sh all not be less than the maximum thickness of 
the cylinder wall. 
4.9.5  Open-Top Tanks 
The top edge of open tanks shall be reinforced by d esign to maintain its shape after installation. 
4.10.  Dimensions and Tolerances 
4.10.1  General 
All dimensions will be taken with the tank in the v ertical position, unfilled. Tank dimensions 
will represent the exterior measurements . The recommended tanks with tolerance of +10%  
are specified in table 1 and 2 below  
Table 1: Cylindrical Vertical Tank 
Volume  
L Diameter  
cm Height  
cm Minimum 
thickness 
mm  Maximum 
thickness 
mm  Weight 
kg 
100 49 71 2.3  2.8  3 
150 58 75 2.5  3.0  4.5 
250 69 84 2.7  3.2  7.0 
500 86 104 2.8  3.3  11 
750 108 100 3.0  3.5  16.5 
1000 108 127 3.7  4.2  21 
1500 126 142 3.8  4.3  29 
2000 138 158 4.0  4.5  35 
2500 148 169 4.1  4.6  45 
3000 158 178 4.2  4.7  55 
4000 176 210 4.5  5.0  73 
5000 185 205 4.8  6.0  85 
6000 252 146 5.0  7.0  108 
6000 198 223 5.0  8.0  108 
8000 219 243 6.0  8.0  159 
10000 285 189 10.0  15.0  205 
10000 238 271 10.0  15.0  205 
16000 290 280 15.0  20.0  325 
24000 356 280 18.0  25.0  550 
Table 2: Rectangular Loft tanks  
Volume 
L Length 
cm Width 
cm Height  
cm Weight  
kg 
250 100 70 55 15 
500 120 88 62 23 
1000 127 127 87 50 
 DUS 1560: 2013 
© UNBS 2013– All rights reserved  8
 4.10.2  Outside Diameter 
The tolerance for the outside diameter, including o ut of roundness, shall be ±3 %. 
4.10.3  Shell Wall and Head Thickness 
The tolerance for average thickness at each elevati on shall be - 10 % of the design thickness on the 
low side and shall be unlimited on the high side. T he tolerance for individual audit readings shall be  
limited to - 20 % of the design thickness. The tota l amount of surface area on the low side of the 
tolerance shall not exceed 10 % of the total surfac e area. 
4.10.4  Placement of Fittings 
The tolerance for fitting placements shall be 12.7 mm in elevation and 2°  radial at ambient 
temperature 
5 Quality of finish 
5.1.  The internal and external surface of water storage  tank shall be smooth, clean and free from 
other hidden internal defects, such as air bubbles,  pits and metallic or other material inclusions.  
5.2  The mould parting line near top rim of the tank sh all be cut and finished to the required level. 
Defects like air bubbles and pits at the parting li ne and at the top of the manhole shall be repaired 
by hot air filler and rod welding method.  
6 Test methods 
6.1 Resistance to deformation test 
6.1.1  When cylindrical vertical water storage tank is te sted in accordance with method 1 described 
in Annex D, the difference between the circumferent ial measurements shall be not greater than 2 % 
of the original measurements.  
6.1.2  When rectangular loft tank is tested in accordance  with method 2 described in Annex D, the 
difference between the longitudinal measurements sh all be not greater than 3 % of the original 
measurements.  
6.2 Tensile strength test 
The tensile strength at yield shall be determined i n accordance with Annex E, and shall be not less 
than 12 N/mm 2. 
6.3 Flexural strength 
The flexural strength shall be determined in accord ance with ISO 1209, Cellular plastics, rigid -
Flexural tests, Parts 1 and 2. The flexural modulus  of the wall of the water tank shall be not less 
than 400 N/mm 2. The manufacturer and/or importer of the raw polye thylene pellets shall be liable to 
supply those that can provide the above-described q uality. 
6.4 Hydrostatic pressure head test 
The tank shall be filled with water up to the nomin al capacity. Thereafter it shall be fitted with a 
pump with a pressure gauge. The pump shall then be started and run till the nominal pressure level 
is attained and examined for leaks. There shall be no leakage observed. A hydrostatic water test will 
be conducted if ordered by the customer. DUS 1560: 2013 
© UNBS 2013– All rights reserved  9
 7 Sampling 
7.1  Lot 
All the water storage tanks of same raw material, s ame type, size and produced under relatively 
uniform conditions of manufacture shall constitute a lot. 
7.1.1 Sample size shall be in accordance with Table 3.  
7.1.2 These tanks shall be selected at random from the lo t. In order to ensure randomness of 
selection, tables of random numbers shall be used.  
7.1.3 Each selected tank, as per Table 3, Column 2, shall  be tested for the requirements in Table 2 
below.  
Table 4 — Scale of sampling and criteria for confor mity for tanks 
Lot size Sample size Acceptance number 
Up to 50 1 0 Failure 
200 2 0 Failure 
300 3 0 Failure 
500 5 0 Failure 
501 and above 8 1 Failure 
 
7.2  Routine test 
 
The routine tests listed in Table 4 shall be carrie d out to ensure that satisfactory quality is 
maintained during a production run. 
 
Table 4 — Routine test parameters 
SL No. Test Clause 
i) Resistance to deformation 6.1 
ii) Hydrostatic pressure head test  6.4 
iii) Carbon black content Annex A 
iv) Carbon black dispersion Annex B 
 
8  Marking 
8.1  All the plastic water storage tanks shall be marked  with the following information: 
i) manufacturer's name and address; 
ii) net capacity, in litres; 
iii) lot number and batch number; 
iv) country of origin; 
v) manufacture date; DUS 1560: 2013 
© UNBS 2013– All rights reserved  10
 vi) material code 
vii)recyclable 
8.2  The marking shall be carried out either by painting , moulding or by sticking the identification marks on 
external surface of the water tank. The marking shall be permanent. 
9  Shipping 
9.1  Since there are variations in methods of shipping a nd handling, the manufacturer’s instructions shall be 
followed in all cases. 
9.2  A suitable means shall be provided, if required, at  the open end of open-top tanks to keep the loaded tank 
rigid. 
9.3  All fittings and flange faces shall be protected fr om damage by covering with suitable plywood, hardbo ard 
or plastic securely fastened. Tanks shall be positi vely vented at all times. 
9.4  Pipe and tubing, fittings and miscellaneous small p arts shall be packaged. Loose items which might 
scratch the interior surface shall not be placed in side the tank during shipment. Additional protectio n, such 
as battens, end wrapping, cross bracing, or other i nterior fastenings shall be used as required to ass ure 
such individual equipment pieces are not damaged in  transit. 
9.5  Upon arrival at the destination, the purchaser shal l be responsible for inspection for damage in trans it. If 
damage has occurred, a claim should be filed with t he carrier by the purchaser. The supplier shall be 
notified if the damage is not first repaired by the  fabricator prior to the tank being put into servic e. The 
purchaser accepts all future responsibility for the  effects of the tank failure resulting from damage.  
9.6  Fittings and accessories that interfere with tank s hipment or could be broken during shipment are ship ped 
separately. 
9.7  The supplier shall provide a brochure to the purcha ser including information on installation instructi ons, 
cleaning procedures, disposal and proper caution an d warning signs. 
10  Workmanship 
10.1  The finished tank wall shall be free, as commercial ly practicable, of visual defects such as foreign 
inclusions, air bubbles, pinholes, pimples, crazing , cracking and delaminations that will impair the 
serviceability of the vessel. 
10.2  All cut edges where openings are cut into the tanks  shall be trimmed smooth. DUS 1560: 2013 
© UNBS 2013– All rights reserved  11
 Annex A 
(normative)  
 
Carbon black content 
A.1 Apparatus 
A.1.1 Combustion boat, made of porcelain or silica, having minimum dimensi ons of 15 mm 
length, 9 mm width and 8 mm height. 
A.1.2 Combustion tube, made of hard glass of approximately 30 mm diameter and 400 ± 50 mm 
length. 
A.1.3 Gas flow meter, for measuring and controlling the rate of flow of n itrogen within 1.7 ± 0.3 
L/s. 
A.1.4 Thermometer, in the range of 250 ° C to 550 ° C. 
A.1.5 Furnace, to accommodate the combustion tube to give temperat ures up to at least 
500 ° C. 
A.2 Reagents 
A.2.1 Nitrogen, as technical grade. A.2.2 Trichloroethylene 
A.3 Procedure 
A.3.1 Assemble the apparatus as shown in Figure 3. Both c old traps following the combustion tube 
shall contain trichloroethylene, but only the first  need be cooled with solid carbon dioxide. 
Alternatively, the entire apparatus may be placed i n a fume hood and the two traps following the 
combustion tube omitted. Fill the dry tube with anh ydrous CaCl 2 or other suitable desiccant. Hold 
between loose plugs of glass wool. 
A.3.2 Heat a clean combustion boat to red heat in a Bunse n flame; then transfer the boat to the 
desiccant and allow it to cool over fresh desiccant . Hold between loose plugs of glass wool. 
A.3.3 Remove the boat from the desiccant and weigh it to the nearest 0.000 1 g. Immediately 
place 1.0 ± 0.1 g of the ethylene plastic under tes t in the boat and quickly weigh to the nearest 
0.000 1 g. 
A.3.4 Heat the furnace to a constant temperature of 600 ° C. Adjust the rate of nitrogen flow to 1.7 
± 0.3 L/min. Open the inlet end of the 2.9-cm diame ter tube, quickly place the combustion boat with 
the sample into the tube at the centre of the furna ce, and adjust the thermocouple so that the weld 
is touching the boat. Insert copper plug, if this i s used. 
Quickly close the furnace and allow heating to proc eed for at least 15 min. 
A.3.5 Move the tube or furnace so that the boat is no lon ger in the heated zone of the furnace and 
allow 5 min for cooling, while maintaining the flow  of nitrogen. Remove the copper plug, if present 
and the boat through the inlet end of the tube and allow it to cool for at least 30 min. Take care tha t 
the boat does not become contaminated from any depo sits on the walls of the tube. Then quickly 
reweigh the boat and its contents to the nearest 0. 000 1 g. DUS 1560: 2013 
© UNBS 2013– All rights reserved  12
 A.3.6 Make all determinations in duplicate.  
A.4 Calculation 
Carbon black content, % by weight =  %100 ×
sWrW  
Where; 
Wr = the mass, in g, of the boat before heating in ai r; 
 Ws = the mass, in g, of the boat after heating in air ; and  
W = the mass,  in g, of the material taken for the test.  
PYRE 
SOLUTION  
 
Figure 4 — Assembly of apparatus for carbon black d etermination DUS 1560: 2013 
© UNBS 2013– All rights reserved  13
 Annex B  (Normative) 
Determination of carbon black dispersion in polyeth ylene materials  
 
B.1 Procedure 
B.1.1 Place two clean microscope slides on a hot plate ma intained at 170 ° C to 210 ° C. Place 
three specimens of pin-head size, each weighing abo ut 5 mg, and each one cut from a separate 
granule, on one of the hot microscope slides, about  20 mm apart. Place a piece of metal shim 40-
mm long, 20-mm wide and 0.03 mm thick at each end a nd cover the whole with the other hot 
microscope slide. Press the specimens by applying e ven pressure for 11/2 to 2 minutes, to the 
whole area of the face of the upper slide. After th e specimens have been placed on the slides, these 
shall not remain on the hot plate for more than 3 m inutes. 
B.1.2 When the slides are cool enough to be handled exami ne the three specimens through a 
microscope at magnification of 200 ± 10 with a fiel d of view of 10.1 mm diameter. Note shall also be 
made of any lack of uniformity of the background. 
B.2 Reporting 
The carbon black dispersion in the material under t est shall be considered to be satisfactory, if the 
specimens show a uniform background free from white  streaks. DUS 1560: 2013 
© UNBS 2013– All rights reserved  14
 Annex C  (Normative) 
Determination of effect of heavy metals on water qu ality  
C.1 Method of extraction C.1.1 Test specimen 
Three test specimens of approximately 500 mm 2 in surface area shall be taken from tank. 
C.1.2 Each test specimen shall be pre-washed for a period  of 6 hours using tap water with pH of 7 
to 8. The water shall be passed through the specime n at a velocity of 50 mm/s while the specimen 
is kept fully immersed with water. After washing, t he specimen shall be filled with fresh solution of 
the distilled water acidified to pH of 4.5 ± 0.1 by  bubbling a current of carbon dioxide through it, a nd 
both ends sealed with a material that does not cont ain any toxic substances nor interfere with the 
determinations of such constituents in the aqueous samples. 
After maintaining the specimens at room temperature  for 48 hours, the solution shall be decanted 
into a suitable container for analysis as the first  extraction. 
The procedure shall be repeated a second and a thir d time. Retain these samples for the 
determination of the amount of metals and other tox ic substances as second and third extractions. 
The first extraction and the third extraction shall  be analyzed for lead. The third extraction shall a lso 
be analyzed for dialkyl tin (C 4 and above) as tin.  
NOTE: When calcium and mercury are present; all thr ee extracts shall be analyzed.  
C.2 Method of analysis 
Analysis for lead, tin, cadmium and mercury shall b e carried out using atomic absorption. DUS 1560: 2013 
© UNBS 2013– All rights reserved  15
 Annex D (Normative) Deformation test 
D.1 Method 1 for cylindrical vertical tank 
D.1.1 The water tank shall be placed on a flat level base . A circumferential measurement shall be 
made parallel to the base at a distance of one thir d the effective height from the bottom. The tank 
shall be filled up to the effective height at a min imum rate of 23 L/min with water at temperature of 
not less than 15 ° C. 
D.1.2 A continuous film of polyethylene shall be floated over the whole of the surface of water in 
tank to prevent evaporation. 
D.1.3  The temperature of the tank and water shall be mai ntained at a temperature not less than 15 ° C and 
after 7 days a circumferential measurement shall be  made at level referred at level to in D.1.1. The 
difference between the two circumferential measurem ents shall be expressed as a percentage of the orig inal 
circumferential measurement. 
D.2  Method 2 for rectangular loft tank 
D.2.1  The rectangular tank shall be placed on a level ba se. The internal length and width of the tank shall  
be measured on the centrelines, as shown in Figure 5 at the centre of effective height. 
 
 
Figure 5 — Centreline measurements 
D.2.2 The tank shall be filled up to the effective height  at a minimum rate of 23 L/min with water at 
a temperature not less than 15 ° C. The lid shall cl ose after filling the loft tank. 
D.2.3 The temperature of the tank and water shall be main tained at not less than 15 ° C and after 7 
days measurements of length and width shall be made  at previously determined centrelines. 
D.2.4 The deformation in each direction shall be calculat ed as follows: 
 
100 212 1×−=LW WDL 
100 211 2×−=WL LDW DUS 1560: 2013 
© UNBS 2013– All rights reserved  16
  
where, 
 
Dl = the deformation of the longer side;  
Dw = the deformation of the shorter side; 
 W1 = the width at the start of the test;  
W2 = the width at the end of test;  
L1  = the length at the start of the test;  
L2 = the length at the end of test. 
Annex E (Normative) Determination of 
tensile properties 
E.1    Definitions E.1.1 
Tensile stress 
Tensile load per unit area of minimum original cros s section within the narrow parallel portion, 
carried by the test specimen at any moment. It is e xpressed in N/mm 2 force per square millimetre). 
 
E.1.2 Elongation 
Increase in distance between references likes on th e narrow parallel portion of the test specimen, 
due to a tensile load, and expressed as a percentag e of the initial distance between the reference 
lines. 
E.1.3 Yield point 
First point on the load/extension curve at which an  increase in extension occurs without an increase 
in load. 
NOTE: In cases where the yield point is not well de fined by the load extension curve, it is frequently  
necessary to define an offset yield point. This is done by specifying a point on the load extension 
curve where the curve departs from linearity by a s pecified percentage elongation or extension (see 
Figure 10). 
E.1.4 Elastic modulus 
 
Ratio of stress to corresponding strain within the range of the greatest stress that the material is 
capable of sustaining without any deviation of prop ortionality of stress to strain. 
E.2 Apparatus 
 
E.2.1 Testing machine, with grips that can be separated at one or more (as  required) of the rates 
given in E.5. 
E.2.1.1 Grips, for holding the test specimen, one being attached t o a fixed or essentially stationary 
member of the machine and the other to a movable me mber. The grips are self-aligning; that is, 
they are attached to the fixed and movable member r espectively in such a manner that they will 
move freely into alignment as soon as any load is a pplied, so that the long axis of the test specimen 
will coincide with the direction of the applied for ce through the centre line of the grip assembly. Th e 
test specimen is held in such a way that slip relat ive to the grips is prevented as far as possible. DUS 1560: 2013 
© UNBS 2013– All rights reserved  17
 E.2.1.2 Load indicator, Suitable load-indicating mechanism capable of showi ng the total tensile 
force carried by the test specimen when held by the  grips. 
This mechanism is essentially free from inertia lag  at the specified rate of testing and indicates the  
force with an accuracy of ± 1 % of the indicated va lue. 
E.2.2 Extension indicator (when required), Suitable instruments for determining, at any time t he 
test, the distance between two fixed points of refe rence lines located within the middle parallel-side d 
pan of the test specimen. It is desirable, but not essential, that this instrument shall automatically  
record this distance (or any change in it) as a fun ction of the force on the test specimen or of the 
elapsed time from the start of the test, or both. I f only distance as, function of elapsed time is 
recorded, force-time data are also taken. The instr ument is essentially free of inertia lag at the 
specified speed of testing and is accurate to ± 1 %  of strain or better. 
The elongations between the reference lines at yiel d and at break of flexible plastics are measured 
to the nearest 7 mm by any convenient means. For th e measurement of modulus of elasticity the 
instrument is capable of measuring the distance bet ween the reference lines to an accuracy of ± 1 
mm. 
E.2.3  Micrometers, dial-gauge micrometer, reading to at least 0.02 mm and provided with a flat 
circular foot that will apply a pressure of 9.81 x 10 -3 to 29.43 x 10 -3 N/mm 2. To the test specimen, for 
measuring the thickness of test specimens of non-ri gid materials. 
E.3 Test specimens 
The test specimen is cut from the obtained flat por tion of the top of the bank with the knife-edged 
die. Reference lines, if used, are 25 ± 1 mm apart and are equidistant from the ends of the middle 
parallel-sided part of the test specimen as shown i n Figure 5. 
E.3.1 It is necessary to apply reference lines to the tes t specimens. This is done with ink or other 
medium that will not affect the material being test ed. Reference lines are not scratched, punched or 
impressed, upon the test specimen. 
E.4 Number of test specimens 
E.4.1 At least five test specimens are tested for each ta nk. 
E.4.2 Test specimens that do not break with parallel port ion are discarded and further test 
specimens are tested. 
E.5    Speed of testing 
E.5.1 The speed of testing is the rate of separation of g rips of the testing machine during the test. 
E.5.2 The speed of testing is preferably chosen from one of the following, but in any' case is 
determined by the specification for the material be ing tested, or by agreement between those 
concerned (see also E.5.2.1): 
E.5.2.1 With some types of testing machines the rates of se paration of grips are virtually the same 
irrespective of whether the machine is running, idl e or under load. With these machines, a ratio of 
separation of grips under load within the above tol erances can be obtained by setting the speed of 
the machine when it is idle. 
E.5.3 If elastic modulus in tension is being determined, the preferred speed of testing is speed A or 
as is specified. Elastic modulus determinations are  made with separate test specimens from those 
used to determine tensile strength and elongation w henever the speeds of testing are not the same. DUS 1560: 2013 
© UNBS 2013– All rights reserved  18
 E.6    Procedure 
E.6.1 Measure the thickness of test specimens at several points to the nearest 1 % with the dial-
gauge micrometer described in E.2.3. The width is t aken to be the width measured to the nearest 
0.05 mm of the middle parallel-sided part of the cu tter shown in Figure 8. 
E.6.2 Place the test specimen in the grips of die testing  machine, taking care to align the long axis 
of the test specimen and the grips with an imaginar y line joining the points of attachment of the grip s 
to the machine. Tighten the grips evenly and firmly  to a degree necessary to prevent the test 
specimen from slipping during the test but not the point where the specimen shall be crushed. 
E.6.3 For the determination of properties other than modu lus of elasticity and for all test specimens 
set the speed of testing at the specified value and  start the machine. 
E.6.3.1 For the test specimens, some or all of, the followi ng shall be noted as required by the 
specification for the material: 
a) load at the yield point (see Note 1); 
b) distance between the reference lines at the yiel d point; 
c) load at break or the maximum load (see Note 2); 
d) distance between the reference lines at break. 
E.6.3.2 The above information can be obtained from an autog raphically recorded stress-strain curve 
or may be directly observed. 
NOTE 1 In cases where the yield point is not well d efined, it is frequently necessary to define an 
offset yield point. This is done by specifying a po int on the load/extension curve where the curve 
departs from linearity by a specified percentage el ongation or extension (see Figure 10). 
NOTE 2 When testing specimens whose cross-sectional  area decreases considerably before break, 
the force may decrease to some extent after having reached a maximum value, so that the 
maximum force and the force at break are not the sa me. For such test specimens the force at break 
cannot be obtained by the use of testing machines t hat only register the maximum force. It is often 
difficult for the load to be read of the moment of break with sufficient accuracy; it is therefore 
recommended that the load at break be determined fr om a force/ extension diagram obtained from a 
tensile testing machine equipped with a recording m echanism. 
E.8 Calculation and expression of results 
E.8.1 Tensile stress at yield, tensile stress at maximum force and tensile stress of break. The force 
at yield or the maximum force, or the force at brea k, as appropriate, is divided by the, original 
minimum cross-sectional area of the test specimen i n square centimetres. The results are 
expressed in N/mm 2. 
 
E.8.2 Elongation at yield and elongation at break 
The extension at the yield point (see Figure 9) or the extension at the moment at break, as 
appropriate, is divided by the original distance be tween the reference lines and multiplied by 100. 
The elongation at yield or break is reported to two  significant figures. 
E.8.3 Elastic modulus 
The elastic modulus is calculated from the initial linear portion of the force Vs extension curve, (se e 
Figure 10) by dividing the difference in stress cor responding to a section of the straight-line by the  DUS 1560: 2013 
© UNBS 2013– All rights reserved  19
 corresponding difference in strain. For this purpos e, the difference in stresses is the difference in 
force divided by the original cross-sectional area of the specimen in square centimetres and the 
difference in strain is the difference in extension  divided by the original distance between the fixed  
points used for the measurement of extension under force. 
E.8.4 For all five specimens, the arithmetic mean of all values is calculated to three significant 
figures (except for elongation for which the mean i s calculated to two significant figures) and 
reported as the "average value" for the particular property in question. 
E.8.5 If the standard deviation (estimated) is required, it is calculated as follows and is reported to 
two significant figures: 
( ) ∑ − − =−1/22n Xn X S  
where 
S = the estimated standard deviation; 
x = the value of single observation; 
n = the number of observations; 
x = the arithmetic mean of the set of observations 
E.9 Test report 
The test report shall include the following as appr opriate: 
a) manufacturer's principle dimensions, etc.; 
b) width and thickness of parallel portions; 
c) method of preparation of test specimen; 
d) conditioning procedures used; 
e) atmospheric conditions in test room; 
f) number of test specimen; 
g) speed of testing; 
h) tensile stress at maximum force or at break, or both average values; 
i) elongation at yield or at break, or both average  values; 
j) elastic modulus, average value; 
k) standard deviations of the individual test resul ts; and 
l) date of test. 
m)  DUS 1560: 2013 
© UNBS 2013– All rights reserved  20
 Dimensions in millimiters 
 
 
 
 
 
 
 
 
TOLERANCE ON DIMENSIONS ± 5 % 
A O VERALL LENGTH , MINIMUM  110 
B W IDTH AT ENDS  20  ± 0.5 
C L ENGTH OF NARROW PARALLEL PORTION  60  ± 0.5 
D W IDTH OF NARROW PARALLEL PORTION  10  ± 0.5 
E R ADIUS , MINIMUM  60 
F T HICKNESS  S EE TEXT  
G D ISTANCE BETWEEN REFERENCE LINES  50  ± 0.5 
H I NITIAL DISTANCE BETWEEN GRIPS  115  ± 5 
Figure 6 — Type 1 test specimen showing positions o f reference lines (if used) 
Dimensions in millimiters 
 
 
 
 
 
 
 
TOLERANCE ON DIMENSIONS ± 5 % 
A O VERALL LENGTH  115 
B W IDTH AT ENDS  25  ± 1 
C L ENGTH OF NARROW PARALLEL PORTION  33  ± 2 
D W IDTH OF NARROW PARALLEL PORTION  6  + 0.4 
E S MALL RADIUS  14  ± 1 
F L ARGE RADIUS  25  ± 2 
G D ISTANCE BETWEEN REFERENCE LINES  25  ± 1 
H I NITIAL DISTANCE BETWEEN GRIPS  80  ± 5 
I T HICKNESS  S EE TEXT  
Figure 7 — Cutting edges of die-type 2 test specime n showing positions of reference lines (if used) 
DUS 1560: 2013 
© UNBS 2013– All rights reserved  21
 Dimensions in millimiters 
 
 
 
 
 
 
 
 
TOLERANCE ON DIMENSIONS ± 5 % 
A O VERALL LENGTH  110 
B W IDTH AT ENDS  45 
C T HICKNESS AT ENDS  6.5 
D L ENGTH OF NARROW PARALLEL PORTION  9.5 
E W IDTH OF NARROW PARALLEL PORTION  25 
F T HICKNESS OF NARROW PORTION  3.2 
G S IDE RADIUS  75 
H FACE RADIUS  75 
J E ND RADIUS  6.5 
Figure 8 — Type 3 test specimen 
Dimensions in millimiters 
Figure 9: Grip for type 3 test specimen 
 
 
DUS 1560: 2013 
© UNBS 2013– All rights reserved  22
 
 
a) for a material for which a yield point can be de termined; and 
b) for a material for which an offset yield point h as to be determined. 
Figure 10: Load/extension diagram DUS 1560: 2013 
© UNBS 2013– All rights reserved  23
 Bibliography 
 
[1] ASTM D, Standard specification for polyethylene  upright storage tanks  
[8] IS, Rotational moulded polyethylene water stora ge tank — specification  
[9] KS 1567, Rotational moulded polyethylene water storage tank — specification 
[9] RS 736, Rotational moulded polyethylene water s torage tank — specification  
 
 DUS 1560: 2013 
© UNBS 2013 – All rights reserved  25
 Certification marking 
Products that conform to Uganda standards may be ma rked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below .  
The use of the UNBS Certification Mark is governed by the Standards Act, and the Regulations made 
thereunder. This mark can be used only by those lic ensed under the certification mark scheme operated by 
the Uganda National Bureau of Standards and in conj unction with the relevant Uganda Standard. The 
presence of this mark on a product or in relation t o a product is an assurance that the goods comply w ith the 
requirements of that standard under a system of sup ervision, control and testing in accordance with th e 
certification mark scheme of the Uganda National Bu reau 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.  
 
 DUS 1560: 2013 
 
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© UNBS 2013 – All rights reserved