DEAS 1151: 2023  
ICS 83.083.01  
 
© EAC 2023                                                                                                                              First Edition 2023 
 DRAFT EAST AFRICAN STANDARD  
Moulded polyethylene water storage tank — Specification  
EAST AFRICAN COMMUNITY  
 
 DEAS 1151: 2023  
ii © EAC 2023 – All rights reserved  
 Copyright notice  
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Reproduction for sales purposes may be subject to royalty payments  or a licensing agreement.  
Violators may be prosecuted . DEAS 1151: 2023  
© EAC 2023 – All rights reserved  iii 
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ .............................  v 
1 Scope ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Terms and definitions  ................................ ................................ ................................ ...........................  1 
4 Types  ................................ ................................ ................................ ................................ ......................  4 
5 Requirements  ................................ ................................ ................................ ................................ .........  4 
5.1 General requirements  ................................ ................................ ................................ ...........................  4 
5.2 Materials  ................................ ................................ ................................ ................................ .................  5 
5.3 Carbon black content  ................................ ................................ ................................ ............................  6 
5.4 Catalyst  ................................ ................................ ................................ ................................ ...................  6 
5.5 Fillers and pigment s ................................ ................................ ................................ ..............................  6 
5.6 Fittings  ................................ ................................ ................................ ................................ ....................  6 
5.7 Sizes ................................ ................................ ................................ ................................ ........................  6 
5.8 Net capacity (actual) ................................ ................................ ................................ ..............................  6 
5.9 Design requirements  ................................ ................................ ................................ .............................  7 
5.9.1  Cylinder shell (unsupported portion of tanks)  ................................ ................................ ...................  7 
5.9.2  Cylinder shell (externally supported tanks)  ................................ ................................ .......................  7 
5.9.3  Top head  ................................ ................................ ................................ ................................ .................  7 
5.9.4  Bottom head  ................................ ................................ ................................ ................................ ...........  7 
5.9.5  Open -top tanks  ................................ ................................ ................................ ................................ ...... 7 
5.10   Dimensions and tolerances  ................................ ................................ ................................ .................  7 
5.10.1  General  ................................ ................................ ................................ ................................ ...................  7 
5.10.2  Outside diameter  ................................ ................................ ................................ ................................ ... 9 
5.10.3  Shell wall and head thickness  ................................ ................................ ................................ ..............  9 
5.10.4  Placement of fittings  ................................ ................................ ................................ .............................  9 
5.11  Mechanical properties ................................ ................................ ................................ ...........................  9 
6 Finish  ................................ ................................ ................................ ................................ ......................  9 
7 Test met hods  ................................ ................................ ................................ ................................ .........  9 
7.1 Resistance to deformation test  ................................ ................................ ................................ ............  9 
7.2 Flexural strength test  ................................ ................................ ................................ ............................  9 
7.3 Test for top load resistance  ................................ ................................ ................................ ...............  10 
7.4 Hydrostatic pressure head test  ................................ ................................ ................................ ..........  10 
8 Sampling  ................................ ................................ ................................ ................................ ..............  10 
8.1 Lot ................................ ................................ ................................ ................................ .........................  10 
8.2 Routine tests  ................................ ................................ ................................ ................................ ........  10 
9 Marking and labelling  ................................ ................................ ................................ ..........................  11 
Annex  A (normative)  Determination of carbon black content  ................................ ................................ .... 12 
A.1 Apparatus  ................................ ................................ ................................ ................................ .............  12 
A.2 Reagents  ................................ ................................ ................................ ................................ ..............  12 
A.3 Procedure  ................................ ................................ ................................ ................................ .............  12 
A.4 Calculation  ................................ ................................ ................................ ................................ ...........  13 
Annex  B (informative)  Determinat ion of effect of heavy metals on water quality  ................................ .... 14 
B.1 Test specimen  ................................ ................................ ................................ ................................ ...... 14 
B.2 Method of extraction  ................................ ................................ ................................ ...........................  14 
B.3 Method of analysis  ................................ ................................ ................................ ..............................  14 
Annex  C (informative)  Deformation test  ................................ ................................ ................................ ....... 15 DEAS 1151: 2023  
iv © EAC 2023 – All rights reserved  
 C.1 Method 1 (for cylind rical vertical tank)  ................................ ................................ .............................  15 
C.2 Method 2 (for rectangular loft tank)  ................................ ................................ ................................ .. 15 
Bibliography  ................................ ................................ ................................ ................................ .....................  17 
 DEAS 1151: 2023  
© EAC 2023 – All rights reserved  v 
 Foreword  
Development of the Ea st African Standards has been necessitated by the need for harmonizing requirements 
governing quality of products and services in the East African Community. It is envisaged that through 
harmonized standardization, trade barriers that are encountered when goods and services are exchanged 
within the Community will be removed.  
The Community has established an East African Standards Committee  (EASC)  mandated to develop and 
issue East African Standards  (EAS) . The Committee is composed of representatives of the  National 
Standards Bodies in Partner States, together with the representatives from the public and private sector 
organizations  in the community .  
East African Standards are developed through  Technical Committees that are representative of key 
stakeholder s including government, academia, consumer groups, private sector and other interested parties. 
Draft East African Standards are circulated to stakeholders through the National Standards Bodies in the 
Partner States. The comments received are discussed and  incorporated before finalization of standards, in 
accordance with the Principles and procedures for develop ment of East African Standards.  
East African Standards are subject to review, to keep pace with technological advances. Users of the East 
African St andards are therefore expected to ensure that they always have the latest versions of the standards 
they are implementing .  
The committee responsible  for this document is Technical Committee EASC /TC 072, Plastics and related 
products  
Attention is drawn to the possibility that some of the elements of this document may be subject of patent 
rights. EAC shall not be held responsible for identifying any or all such patent rights.  
 DRAFT EAST  AFRICAN STANDARD  DEAS 1151: 2023  
 
© EAC 2023 – All rights reserved  1 
 Moulded polyethylene water storage tank — Specification  
1 Scope  
This Draft East African  Standard specifies requirements, sampling and test methods for moulded polyethylene 
water storage tanks (closed and open top tank).  
This standard is not applicable to underground tanks, mobile water tanks and horizontal cylindrical water 
tanks.  
2 Normative references  
The following documents are referred to in the text in such a way that some or all of their content constitutes 
requirements of this document.  For dated references, only the edition cited applies. For undated references, 
the la test edition of the referenced document (including any amendments) applies.  
ISO 1133 -1, Plastics — Determination of the melt mass -flow rate (MFR) and melt volume -flow rate (MVR) of 
thermoplastics — Part 1: Standard method   
ISO 1183 -1, Plastics — Methods fo r determining the density of non -cellular plastics — Part 1: Immersion 
method, liquid pycnometer method and titration method   
ISO 4892 -2, Plastics — Methods of exposure to laboratory light sources — Part 2: Xenon -arc lamps   
ISO 13274, Packaging — Transport  packaging for dangerous goods — Plastics compatibility testing for 
packaging and IBCs   
ISO 18872, Plastics — Determination of tensile properties at high strain rates   
ISO 23900 -3, Pigments and extenders — Methods of dispersion and assessment of dispersibi lity in plastics — 
Part 3: Determination of colouristic properties and ease of dispersion of black and colour pigments in 
polyethylene by two -roll milling   
US ISO 1209 -1, Rigid cellular plastics — Determination of flexural properties — Part 1: Basic bendin g test   
US ISO 1209 -2, Rigid cellular plastics — Determination of flexural properties — Part 2: Determination of 
flexural strength and apparent flexural modulus of elasticity  
3 Terms and definitions   
For the purposes of this document, the following terms a nd definitions apply.  
ISO and IEC maintain terminological databases for use in standardization at the following addresses:  
— ISO Online browsing platform: available at http://www.iso.org/obp   
2 © EAC 2023 – All rights reserved  
 3.1  
net capacity (actual)  
net total volume of water contained between the lowest level of the overflow and lowest level of outlet (see 
Figure 1 and Figure 2)  
3.2  
gross capacity/nominal capacity  
total enclosed volume of the tank including any space  
Note 1 to e ntry: The space may not be capable of being filled with water.  
3.3  
mould parting line  
circumferential line visible only on the external surface of the tank corresponding to a parting joint of the mould 
required for rotational moulding (see Figure 1 and F igure 2)  
3.4  
overall height  
height  of the finished empty tank at its highest point, including the top rim of the manhole and lid of the tank 
(see Figure 1 and Figure 2)  
3.5  
effective height  
height of the finished empty tank from its base to the point w here overflow connection is provided for the 
purpose of limiting water storage capacity (see Figure 1 and Figure 2)  
3.6  
overall diameter  
maximum outer diameter of the finished empty tank measured at its base (see Figure 1 and Figure 2)  
3.7  
manhole/hand hold hole  
hole of suitable internal diameter provided at the top of the tank for the purpose of inspection of internal 
surface and entry into the tank (see Figure 1)  
3.8  
interna l diameter of manhole/hand -hole 
internal diameter of the rim of the manhole m easured as the mean of two perpendicular diameters (see Figure 
1 and Figure 2)  
3.9  
closed tank  
tank moulded as a single piece with the top as an integral part (see Figure 1)  
3.10  
open top tank  
tank where the body and top are moulded separately and asse mbled after moulding (see Figure 2)  
3.11  
rotational moulding  
commercial process consisting of loading the mould with powdered resin, fusing the resin by heating while 
rotating the mould about more than one axis, and cooling and removing the moulded arti cle  
3.12  
blow moulding  
method of forming hollow objects by inflating a parison into a mould with compressed gas   
© EAC 2023 – All rights reserved  3 
 3.13  
elongation  
increase in distance between references likes on the narrow parallel portion of the test specimen, due to a 
tensile load, and expressed as a percentage of the initial distance between the reference lines  
 
Key 
RCC   Reinforcement  
PCC   Pre-cast cement concrete  
Figure 1 — Typical view of closed top tank  
 
Figure 2 — Typical  view of open top tank  
 
4 © EAC 2023 – All rights reserved  
 4 Types  
There shall be two types of tanks namely:  
a) cylindrical vertical tanks (closed and open -end); and  
b) rectangular loft tanks [see Figure 3 a) and b)].  
 
Figure 3a) — Cylindrical vertical with closed to p 
 
Figure 3 b) — Rectangular loft tank  
5 Requirements  
5.1 General requirements  
5.1.1  The following conditions apply to both open -top and closed -top water storage tanks:  
a) own hydrostatic head of water; and  
b) uniform flat base sup port; 
 
© EAC 2023 – All rights reserved  5 
 5.1.2  The nominal service temperature shall be 1 °C ─ 50 °C.  
5.1.3  The lid of the tank shall fit securely over the top rim of the tank, and it shall rest evenly on it in order to 
prevent the ingress of foreign matter such as insects, mosquitoes or d ust through the top of the tank. The lid 
shall be provided wi th suitable locking arrangement.  
5.2 Materials  
5.2.1  The materials for construction of the tank and lid that come into contact with water shall be of food 
grade and shall meet the material requi rements given in Table 1 . 
Table 1 — Requirements for materials  
Material type  Property  Requirement  Test method  
Blow -moulded 
polyethylene  Densitya, kg/m3, min  938 ISO 1183 -1 
Melt flow rateb at 190 °C and 21.6 kg, max.  12 g/10, mind ISO 1133 -1 
Tensile st rengthc at yield, MPa, min. 21 ISO 18872  
Elongationc  Elongation at 
yield shall not 
be more than 15 
% 
 Elongation at 
break shall not 
be less than 200 
% 
Rotationally 
moulded 
polyethylene  Densitya, kg/m3, min.  930 ISO 1183 -1 
Melt flow rateb at 190 ºC a nd 2.16 kg  4.0 g/10 min ± 3.0 g/10 
mine ISO 1133 -1 
Tensile 
strengthc At yield, MPa, min.  15 ISO 18872  
Elongation  Elongation at yield, %, max . 25 
Elongation at break, %, min.  200 
Blow -moulded 
polyethylene 
and 
rotationally 
moulded 
polyethylene  Stress 
cracking 
resistance  After 28 days immersion, tensile 
strength, of the reference sample 
without pin impression, %, min.  85 ISO 13274  
Time to 50 % failure, h, min . 500 
Time to failure at reference stress, 9 
MPa, h, min . 20 
Weather 
resistancec For external installations after 
exposure to global irradiance of 34 
GJ/m2 (corresponding to an irradiance 
of 2.3 GJ/m² for the band from 300 
nm to 400 nm), elongation at break, of 
the initial value, %, min . 50 ISO 4892 -2 
For internal installations,  elongation at 
break after exposure to global 
irradiance of 3.4 GJ/m2 
(corresponding to an irradiance of 
0.23 GJ/m² for the band from 300 nm 
to 400 nm), of the initial elongation at 
break, %, min . 50 
a Test to be carried out on raw material   
6 © EAC 2023 – All rights reserved  
 b Test to  be carried out on raw material and on tank . 
c Test to be carried out on tank . 
d Maximum increase of the melt flow rate of the moulded tank shall not be greater than 15 % of the value determined on the raw 
material. e Maximum variation of the melt flow  rate of the moulded tank shall not be greater than 20 % of the value determined on the raw 
material.  
 
5.2.2  Water tanks meant for outdoor use shall be manufactured from virgin polyethylene materials. The 
outer layer of the tank, however, shall be made fr om virgin and 10 % maximum recycled material. The inside 
layer shall be made of 100 % virgin material.  
5.2.3  All polyethylene resin materials shall contain a minimum of UV 8 stabilizer as compounded by the 
resin manufacturer.  
5.2.4  The material for const ruction of the tank and lid, which comes into contact with water, shall not impart 
any taste, colour or odour to water; they shall neither have any toxic effect nor contaminate water thereby 
making it unpotable.  
5.2.5  The life span for the tank shall not be less than 15 years under normal use  
5.3 Carbon black content  
5.3.1  For tanks intended to be used outdoors, carbon black pigment shall be added to the moulding 
material for the outer layer or the exposed layer and shall be 2.5 % ± 0.5 % when tested in a ccordance with 
Annex A.  
5.3.2  The carbon black or any other pigment added shall be uniformly dispersed in the material, when 
tested in accordance with Method A of ISO 23900 -3. 
5.4 Catalyst  
The total amount of inorganic material present in polyethylene s hall not exceed 0.2 % (m/m) when tested by 
the Atomic Absorption Method and in accordance with Annex B. An alternative method of testing for the 
metals shall be by X -ray fluorescence, where the Atomic Absorption Method may not be applicable or just 
non-operational.  
5.5 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 shall not exceed 0.5 % dry blended, and 2 % compounded in, of the 
total w eight.  
5.6 Fittings  
It shall be the prerogative of the manufacturer to provide as much information as is possible to the consumer 
regarding fittings.  
5.7 Sizes  
Tank sizes will vary in accordance with the customer's requirements and shall be as given in  5.10.  
5.8 Net capacity (actual)  
When filled to the lowest level of overflow, and the volume attained measured, tanks shall discharge the 
capacity marked on them.   
© EAC 2023 – All rights reserved  7 
 5.9 Design requirements  
5.9.1  Cylinder shell (unsupported portion of tanks)  
5.9.1.1  The minimum wall thicknesses of the tanks shall be as given in Table 2 and Table 4.  
5.9.1.2  The hydrostatic design stress that is used to determine the minimum wall thickness at any fluid 
level shall be based on hoop stress data for the polyethylene materials . The hydrostatic design -basis shall be 
reduced by a service factor to determine the actual hydrostatic design stress. The maximum service factor 
shall be 0.5 for wall thicknesses less than 9.5 mm. For thicknesses equal to or greater than 9.5 mm, the 
maxim um service factor shall be 0.475.  
5.9.1.3  Tank hoop stresses shall be derated for service above 23 °C.  
5.9.2  Cylinder shell (externally supported tanks)  
The minimum required wall thickness for the cylinder straight shell shall be sufficient to support i ts own weight 
in an upright position without any external support. The tolerance indicated in 5.10.3 applies to these 
dimensions . 
5.9.3  Top head  
The top head shall be integrally moulded with the cylinder shell. The minimum thickness of the top head shall 
be equal to the top of the straight wall.  
5.9.4  Bottom head  
The bottom head shall be integrally moulded with the cylinder shell. The radius of the bottom knuckle of a flat  
bottom tank shall not be less than 25.4 mm for tanks with a diameter less than 1.8  m, and 38.1 mm for a 
diameter greater than 1.8 m. The minimum thickness of the radius shall not be less than the maximum 
thickness of the cylinder wall.  
5.9.5  Open -top tanks  
The top edge of open tanks shall be reinforced by design to maintain its shape after installation.  
5.10  Dimensions and tolerances  
5.10.1  General  
All dimensions shall be taken, with the tank in the vertical position, unfilled. Tank dimensions shall represent 
the exterior measurements. The thickness shall be as specified in Table 2  for rotational moulded tanks and 
Table 4 for blow -moulded tanks . 
Table 2 — Dimensions for rotational moulded cylindrical vertical tank  
Volume  
L Minimum thickness  
mm Mass  
kg 
100 2.3 3 
150 2.5 4.5 
250 2.7 7.0 
500 2.8 11 
750 3.0 16.5  
8 © EAC 2023 – All rights reserved  
 1 000  3.7 21 
1 500 3.8 29 
2 000  4.0 35 
2 500  4.1 45 
3 000  4.2 55 
4 000  4.5 73 
5 000  4.8 85 
6 000  5.0 108 
8 000  6.0 159 
10 000  10.0 205 
16 000  15.0 325 
24 000  18.0 550 
 
Table 3 — Recommended masses for rotational moulded rectangular loft tanks  
Volume  
L Mass  
kg 
250 15 
500 23 
1000  50 
 
Table 4 — Recommended dimensions for blow -moulded cylindrical vertical tank  
Volume  
L Minimum thickness  
mm Mass  
kg 
Top wall  Side wall  Bottom wall  
250 1.6 2.0 2.2 6 
500 2.0 2.1 2.3 9 
1 000  2.2 2.5 2.8 16 
1 500  2.3 2.8 3.2 24 
2 000  2.6 3.0 3.8 32 
2 500  2.8 3.0 4.0 40 
3 000  3.1 3.4 4.3 48 
4 000  3.5 3.7 5.3 64 
5 000  3.5 3.9 5.5 80 
8 000  3.5 4.0 5.8 130 
10 000  4.5 5.0 5.8 170 
  
© EAC 2023 – All rights reserved  9 
 5.10.2  Outside diameter  
The tolerance for the outside diameter, including out of roundness, shall  be ±3 %.  
5.10.3  Shell wall and head thickness  
The tolerance for average thickn ess at each elevation shall be −10 % of the design thickness on the low side 
and shall be unlimited on the high side. The tolerance for individual audit readings shall be limi ted to -20 % of 
the design thickness. The total amount of surface area on the low side of the tolerance shall not exceed 10 % 
of the total surface area.  
5.10.4  Placement of fittings  
The tolerance for fitting placements shall be 12.7 mm in elevation and 2 ° radial at ambient temperature.  
5.11 Mechanical properties  
5.11.1  The flexural modulus of the wall of the water tank shall not be less than 400 N/mm2 when d etermined 
in accordance with ISO 1209 -1 and ISO 1209 -2. 
5.11.2  When the cylindrical vertical wa ter storage tank is tested in accordance with Method 1, in Annex C, 
the difference between the circumferential measurements shall not be greater than 2 % of the original 
measurements.  
6 Finish  
6.1 The internal surface of the water storage tank shall be s mooth to the extent that nothing sticks to it, and 
easily cleanable, clean and free from other hidden internal defects, such as air bubbles, pits and metallic or 
other material inclusions . 
6.2 The mould parting line near the top rim of the tank shall be cu t and finished to the required level. 
Defects like air bubbles and pits at the parting line and at the top of the manhole shall be repaired.  
6.3 The finished tank wall shall be free, as commercially practicable, of visual defects such as foreign 
inclusion s, air bubbles, pinholes, pimples, crazing, cracking and delamination that will impair the serviceability 
of the tank . 
6.4 All cut edges where openings are cut into the tanks shall be trimmed, smooth . 
7 Test methods  
7.1 Resistance to deformation test  
7.1.1 The resistance to deformation test shall be determined in accordance with Method 1 of Annex C.  
7.1.2  When a rectangular loft tank is tested in accordance with Method 2 of Annex C, the difference 
between the longitudinal measurements shall not be great er than 3 % of the original measurements.  
7.2 Flexural strength test  
The flexural modulus of the wall of the water tank shall be d etermined in accordance with ISO 1209 -1 and ISO 
1209 -2.  
10 © EAC 2023 – All rights reserved  
 7.3 Test for top load resistance  
The tank shall be filled to 98 % of its net capacity and shall be subjected for not less than 4 h at outdoor 
temperature to compression by means of 100 -kg load applied on the horizontal surface, provided for a man to 
stand before entering the tank. After removal of the load, the test spec imen shall be inspected for deformation 
or crack on the surface and after 4 h of the removal of the load, the flat surface shall return to normal position. 
This test shall be applied to tanks with capacity of 3 000 L and more.  
7.4 Hydrostatic pressure hea d test  
The tank shall be filled with water up to the nominal 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 leakage. There sha ll be no leakage observed. A hydrostatic water test will be conducted if 
requested by the customer.  
8 Sampling  
8.1 Lot 
8.1.1  All the water storage tanks of same raw material, same type, size and produced under relatively 
uniform conditions of manufactur e shall constitute a lot.  
8.1.2  The sample size shall be determined in accordance with Table . 
Table 5 — Scale of sampling and criteria for conformity of tanks  
Lot size  Sample size  Maximum possible failure  
Up to 50  1 0 
200 2 0 
300 3 0 
500 5 0 
501 and above  8 1 
 
8.1.3  Tanks shall be selected at random from the lot. In order to ensure randomness of selection, tables of 
random numbers shall be used.  
8.1.4  Each tank selected in accordance with Table 5 shall be tested for the requirements in Table 6.  
Table 6 ─ Routine test parameters  
Test Test method  
Resistance to deformatio n 7.1 
Hydrostatic pressure head test  7.3 
Carbon black content  Annex A  
Carbon black dispersion  ISO 23900 -3 
8.2 Routine tests  
The routine tests listed in Table 6 shall be carried out t o ensure that satisfactory quality is maintained during a 
production run.   
© EAC 2023 – All rights reserved  11 
 9 Marking and labelling  
9.1 Plastic water storage tanks shall be marked legibly and indelibly in English and/or any other official 
language (French, Kiswahili, etc.) used in the imp orting East African Partner State with the following 
information with the:  
a) manufacturer's name or trade mark ;  
b) net capacity  in litres ; 
c) country of origin ; and 
d) code of resin identification and symbol for recycling in accordance with EAS 1086 . 
9.2 Plastic  water storage tanks shall be labelled legibly and indelibly in English and/or any other official 
language (French, Kiswahili, etc.) used in the importing East African Partner State with the following 
information with the:  
a) name of product as, “plastic tank ”; 
b) name and physical address of manufacturer;  
c) lot number and/or batch number; and  
d) manufacture date .  
12 © EAC 2023 – All rights reserved  
 Annex  A 
(normative)  
 
Determination of carbon black content  
A.1 Apparatus  
A.1.1  Combustion boat , made of porcelain or silica, having minimum dimensions 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 mm ± 50 mm 
length  
A.1.3  Gas flow meter , for measuring and controlling the rate of flow of nitrogen within 1.7 L/s ± 0.3 L/s  
A.1.4  Thermometer , in the range of 250 °C - 550 °C  
A.1.5  Furnace , to accommodate the combustion tube to give temperatures 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 app aratus as shown in Figure A.1. Both cold traps following the combustion tube shall 
contain trichloroethylene, but only the first needs be cooled with solid carbon dioxide. Alternatively, the entire 
apparatus may be placed in a fume hood and the two traps f ollowing the combustion tube omitted. Fill the dry 
tube with anhydrous CaCl 2 or other suitable desiccant. Hold between loose plugs of glass wool . 
 
Figure A.1 ─ Assembly of apparatus for carbon black determination  
 
© EAC 2023 – All rights reserved  13 
 A.3.2  Heat a clean combustion boat to red hot in a Bunsen flame; 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 g ± 
0.1 g of the ethylene plastic under test 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 th e rate of nitrogen flow to 1.7 L/min ± 
0.3 L/min. Open the inlet end of the 2.9 -cm diameter tube, quickly place the combustion boat with the sample 
into the tube at the centre of the furnace, and adjust the thermocouple so that the weld is touching the boa t. 
Insert a copper plug, if this is used. Quickly close the furnace and allow heating to proceed for at least 15 min.  
A.3.5  Move the tube or furnace so that the boat is no longer in the heated zone of the furnace and allow 5 
min for cooling, while maintai ning 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 that the boat does not 
become contaminated from any deposits on the walls of the tube. Then qui ckly reweigh the boat and its 
contents to the nearest 0.000 1 g.  
A.3.6  Make all determinations in duplicate.  
A.4 Calculation  
The carbon black content, expressed as a percentage, shall be calculated using the formula below:  
 
where 
W is carbon black content, by percent weight;  
Wr is the mass, in grams, of the boat before heating in air;  
Ws is the mass, in grams, of the boat after heating in air .  
14 © EAC 2023 – All rights reserved  
 Annex  B 
(informative)  
 
Determination of effect of heavy  metals on water quality  
B.1 Test specimen  
Three test specimens of approximately 500 mm2 in surface area shall be taken from the tank.  
B.2 Method of extraction  
B.2.1  Each test specimen shall be pre -washed for a period of 6 h using tap water with pH of 7 to 8. The 
water shall be passed through the specimen at a velocity of 50 mm/s while the specimen is kept fully 
immersed in water. After washing, the specimen shall be filled with fresh solution of the distilled water acidified 
to pH of 4.5 ± 0.1 by bubbl ing a current of carbon dioxide through it, and both ends sealed with a material that 
does not contain any toxic substances or interfere with the determinations of such constituents in the aqueous 
samples.  
B.2.2  After maintaining the specimens at room temp erature for 48 h, the solution shall be decanted into a 
suitable container for analysis as the first extraction.  
B.2.3  The procedure shall be repeated a second and a third time. Retain these samples for the 
determination of the amount of metals and other toxic substances as second and third extractions.  
B.2.4  The first extraction and the third extraction shall be analysed for lead. The third extraction shall also 
be analysed for dialkyl tin as tin.  
B.2.5  When calcium and mercury are present, all three ex tracts shall be analysed.  
B.3 Method of analysis  
Analysis for lead, tin, cadmium and mercury shall be carried out using atomic absorption.   
© EAC 2023 – All rights reserved  15 
 Annex  C 
(informative)  
 
Deformation test  
C.1 Method 1 (for cylind rical vertical tank)  
C.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 third, the effective height from the bottom. The tank shall be filled up 
to the effective  height at a minimum rate of 23 L/min with water at a temperature of not less than 15 °C.  
C.1.2  A continuous film of polyethylene shall be floated over the whole of the surface of water in tank to 
prevent evaporation.  
C.1.3  The temperature of the tank an d water shall be maintained at a temperature not less than 15 °C and 
after seven days, a circumferential measurement shall be made at a level referred to in C.1.1. The difference 
between the two circumferential measurements shall be expressed as a percenta ge of the original 
circumferential measurement.  
C.2 Method 2 (for rectangular loft tank)  
C.2.1  The rectangular tank shall be placed on a level base. The internal length and width of the tank shall 
be measured on the centrelines, as shown in Figure C.1, a t the centre of effective height . 
 
Figure C.1 — Centreline measur e 
C.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 close afte r filling the loft tank.  
C.2.3  The temperature of the tank and water shall be maintained at not less than 15 °C and after seven 
days, measurements of length and width shall be made at previously determined centrelines.  
C.2.4  The deformation in each direc tion, expressed as a percentage, shall be calculated using the formula 
below  
 
Dw is the deformation, in percentage, for the shorter side;  
L2 is the length, in millimetres, of the tank at the end of test;  
L1 is the length, in millimetres, of the tank at the start of the test; and  
 
16 © EAC 2023 – All rights reserved  
 W1 is the width, in millimetres, of the tank at the start of the test.   
© EAC 2023 – All rights reserved  17 
 Bibliography  
[1] RS 128 : 2019, Rotational moulded polyethylene water storage tanks — Specification  
[2] TZS 892 -1: 2019, Polyethylene tanks for storage of potable water — Part 1: Specifications  
[2] US 1560: 2022 , Moulded polyethylene water storage tank — Specification  
 DEAS 1151: 2023    
 
© EAC 2023 – All rights reserved