 DRAFT UGANDA STANDARD  
  DUS 1560  
Second Edition  
2020 -10-06 
 
 
 Reference number  
WDUS 1560: 2020  
© UNBS 2020   
  
Moulded polyethylene water storage tank — Specification  
 WDUS 1560 : 2020  
ii © UNBS 2020  – 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 yyyy  
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, including photocopying and microfilm, without prior w ritten 
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 4 333 2 50/1/2/3  
Fax: +256 41 4 286 123  
E-mail: info@unbs.go.ug  
Web: www.unbs.go.ug  WDUS 1560: 2020  
© UNBS 2020  – All rights rese rved iii 
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ .............................  v 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Terms and definitions  ................................ ................................ ................................ ...........................  1 
4 Types ................................ ................................ ................................ ................................ ......................  4 
5 Requirements  ................................ ................................ ................................ ................................ .........  5 
5.1 General  ................................ ................................ ................................ ................................ ...................  5 
5.2 Materials  ................................ ................................ ................................ ................................ .................  5 
5.3 Carbon black content  ................................ ................................ ................................ ............................  7 
5.4 Catalyst  ................................ ................................ ................................ ................................ ...................  8 
5.5 Fillers and pigments  ................................ ................................ ................................ ..............................  8 
5.6 Fittings  ................................ ................................ ................................ ................................ ....................  8 
5.7 Sizes ................................ ................................ ................................ ................................ ........................  8 
5.8 Net capacity (actual) ................................ ................................ ................................ ..............................  8 
5.9 Design requirements  ................................ ................................ ................................ .............................  8 
5.9.1  Cylinder shell (unsupported portion of tanks)  ................................ ................................ ...................  8 
5.9.2  Cylinder shell (e xternally supported tanks)  ................................ ................................ .......................  8 
5.9.3  Top head  ................................ ................................ ................................ ................................ .................  8 
5.9.4  Bottom head  ................................ ................................ ................................ ................................ ...........  8 
5.9.5 Open -top tanks  ................................ ................................ ................................ ................................ ...... 9 
5.10  Dimensions and tolerances  ................................ ................................ ................................ ..................  9 
5.10.1  General  ................................ ................................ ................................ ................................ ...................  9 
5.10.2  Outside diameter  ................................ ................................ ................................ ................................ . 10 
5.10.3  Shell wall and head thickness  ................................ ................................ ................................ ............  10 
5.10.4  Placement of fittings  ................................ ................................ ................................ ...........................  10 
5.11  Mechanical properties ................................ ................................ ................................ .........................  11 
6 Finish  ................................ ................................ ................................ ................................ ....................  11 
7 Test methods  ................................ ................................ ................................ ................................ ....... 11 
7.1 Resistance to deformation test  ................................ ................................ ................................ ..........  11 
7.2 Tensile strength test  ................................ ................................ ................................ ...........................  11 
7.3 Flexural strength test  ................................ ................................ ................................ ..........................  11 
7.4 Hydrostatic pressure head test  ................................ ................................ ................................ ..........  11 
8 Sampling  ................................ ................................ ................................ ................................ ..............  12 
8.1 Lot ................................ ................................ ................................ ................................ .........................  12 
8.2 Routine tests  ................................ ................................ ................................ ................................ ........  13 
9 Marking  ................................ ................................ ................................ ................................ .................  13 
Annex  A (normative)  Determination of carbon black content  ................................ ................................ .... 14 
A.1 Apparatus  ................................ ................................ ................................ ................................ .............  14 
A.2 Reagents  ................................ ................................ ................................ ................................ ..............  14 
A.3 Procedure  ................................ ................................ ................................ ................................ .............  14 
A.4 Calculation  ................................ ................................ ................................ ................................ ...........  15 
Annex  B (normative)  Determination of effect of heavy metals on water quality  ................................ ...... 16 
B.1 Test specimen  ................................ ................................ ................................ ................................ ...... 16 
B.2 Method of extraction  ................................ ................................ ................................ ...........................  16 
B.3 Method of analysis  ................................ ................................ ................................ ..............................  16 
Annex  C (normative)  Deformation test  ................................ ................................ ................................ ..........  17 WDUS 1560 : 2020  
iv © UNBS 2020  – All rights reserved  
 C.1 Method 1 for cylindrical vertical tank  ................................ ................................ ...............................  17 
C.2 Method 2 for rectangular  loft tank  ................................ ................................ ................................ ..... 17 
Bibliography  ................................ ................................ ................................ ................................ .....................  19 
 WDUS 1560: 2020  
© UNBS 2020  – All rights rese rved v 
 Foreword  
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry of Trade , Industry and 
Cooperatives establish ed under Cap 327 , of the Laws of Uganda , as amended .  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 Alimentarius Commission o n Food Standards, and  
(c) the National Enquiry Point on TBT  Agreement  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 given field or area and consists of key stakeholders 
including government, academia, consumer groups, private sector and other interested parties.  
Draft Uganda Standards adopted by the Technical Committee 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.  
The committee responsible for this document is Technical Committee UNBS/TC 04, Mechanical Engineering 
and M etallurgy  
This second  edition cancels and replaces the first  edition ( US 1560: 20 13), which has been technically 
revised.  
 WORKING DRAFT UGANDA STANDARD  WDUS 1560:2020  
 
© UNBS 2020 – All rights reserved  1 
 Moulded polyethylene water storage tank — Specification  
1 Scope  
This Working Draft Uganda Sta ndard specifies the requirements and methods of sampling and test for 
moulded polyethylene water storage tanks (closed and open top tank).  
This draft standard is not applicable to underground tanks, mobile water tanks and horizontal cylindrical water 
tanks . 
2 Normative references  
The following referenced documents 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  latest edition of the referenced document (including any amendments) applies.  
ISO 18872, Plastics — Determination of tensile properties at high strain rates  
ISO 6964, Polyolefin pipes and fittings — Determination of carbon black content by calcination and  pyrolysis 
— Test method  
ISO 18553, Method for the assessment of the degree of pigment or carbon black dispersion in polyolefin 
pipes, fittings and compounds  
US ISO 1209 -1, Rigid cellular plastics — Determination of flexural properties — Part 1: Basic bend ing test  
US ISO 1209 -2, Rigid cellular plastics — Determination of flexural properties — Part 2: Determination of 
flexural strength and apparent flexural modulus of elasticity  
ISO 1183 -1 
ISO 18872  
 
3 Terms and definitions  
For the purposes of this document,  the followi ng terms and definitions apply.  
ISO and IEC maintain terminological databases for use in standardizat ion at the following addresses:  
— ISO Online browsing platform: available at http://www.iso.org/obp  
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)   
2 © UNBS 2020  – All rights  reserved  
 3.2 
gross capacity (nominal  
total enclosed volume of the tank including any space, which may not be capable of being filled with water  
3.3 
mould parting  
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 Figure 2)  
3.4 
overall height  
height of the finished empty tank at its highes t 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 where 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 finished empty tank measured at its base (see Figure 1and Figure 2)  
3.7 
man-hole/hand -hole 
hole of suitable internal diameter provided at the top of the tank for the purpos e of inspection of internal 
surface and entry into the tank (see Figure 1)  
3.8 
internal diameter of man -hole/hand -hole 
internal diameter of the rim of the manhole measured as the mean of two perpendicular diameters (see 
Figures 1 and 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 moulded separately and assembled after moulding (see Figure 2)  
3.11 
rotational moulding  
three -stage 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 article  
3.12  
blow moulding  
method of forming hollow objects by inflating a parison into a mould with  compressed gas  WDUS 1560: 2020  
© UNBS 2020  – All rights reserved  3 
 
 
Key 
RCC  Reinforcement  
PCC  Pre-cast cement concrete  
NOTE  The requirements for the construction of the reinforced cement concrete or pre -cast cement concrete depend 
on the capacity of the tank and location.  
Civil engineering will establish the viability of the geology that the water tank will be placed on and this will 
dictate site preparation and cost.  
The choice of materials of construction will be impacted by the whether the tank is located indoors, outdoors 
or underground.  
Figure 1 — Typical perspective view of closed top tank   
4 © UNBS 2020  – All rights  reserved  
 
 
Figure 2 — Typical view of open top tank  
 
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)) . WDUS 1560: 2020  
© UNBS 2020  – All rights reserved  5 
 
 
Figure 3 — Types of water storage tanks  
5 Requirements  
5.1 General  
5.1.1  The following two conditions apply to both open -top and closed -top water storage tanks:  
a) own hydrostatic head of water; and  
b) uniform flat base support  
5.1.2  The nominal service temperature shall be  1 °C - 50 °C  
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 requirements gi ven in Table 1 . 
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 from virgin and 10 % reusable material.  The inside layer shall 
be made of 100% virgin mate rial. 
5.2.3  All polyethylene resin material shall contain a minimum of a U.V 8 stabilizer as compounded by the 
resin manufacturer.  
5.2.4  The material for construction of the tank and lid, which comes into contact with water, shall not impart 
any taste, col our 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 .  
6 © UNBS 2020  – All rights  reserved  
 Table 1 — Requirements of materia l 
Material type  Property  Requirement  Test 
method  
Blow -moulded 
polyethylene  Density a shall not be less than 938 kg/m3 ISO 1183 -1 
Melt flow rate 
b shall be less than 12 g/10 min at 190 ºC, 21.6 kg 
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  ISO 1133 -1 
Tensile 
strength c tensile strength at yield shall not be less than 21 MPa  ISO 18872  
 elongation at yield shall not be more than 15 %  
elongation at break shall not  be less than 200 %  
Rotationally moulded 
polyethylene  Density a shall not be less than 930 kg/m3  ISO 1183 -1 
Melt flow rate  
b shall be 4.0 g/10 min ± 3 .0 g/10  min at 190 ºC, 2 .16 kg. 
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  ISO 1133 -1 
Tensile 
strength c tensile strength at yield shall not be less than 15 MPa  
elongation at yield shall not be more than 25 %  
elongation at break shall not be less than 200 %  ISO 18 872 
Blow -moulded 
polyethylene and 
rotationally moulded 
polyethylene  Stress 
cracking 
resistance  either:  
After 28 days immersion the tensile strength shall not be 
less than 85 % of the reference sample without pin 
impression  
or 
the time to 50 % failure shal l not be less than 500 h  
or 
the time to failure at reference stress 9 MPa shall not be 
less than 20 h  ISO 23667  
Weather 
resistancec For external installations after exposure to global 
irradiance of 34 GJ/m2 (corresponding to an irradiance of 
2.3 GJ/m² fo r the band from 300 nm to 400 nm) the 
elongation at break shall be greater than 50 % of the 
initial value.  
For internal installations the 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) shall be greater than 50 % ISO 4892 -2 WDUS 1560: 2020  
© UNBS 2020  – All rights reserved  7 
 Material type  Property  Requirement  Test 
method  
of the initial elongation at break.  
Weather 
resistance  c For external installations after exposure to global 
irradiance of 34 GJ/m2 (corresponding to an irradiance 
of 2.3 GJ/m² for th e band from 300 nm to 400 nm) the 
elongation at break shall be greater than 50 % of the 
initial value.  
For internal installations the 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) shall be greater than 50 % 
of the initial elongation at break.  ISO 4892 -2 
Weather 
resistance  c For external installations after exposure to global 
irradiance of 34 GJ/m2 (corresponding to an irradiance 
of 2.3 GJ/m² for the ba nd from 300 nm to 400 nm) the 
elongation at break shall be greater than 50 % of the 
initial value.  
For internal installations the 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) shall be greater than 50 % 
of the initial elongation at break.  ISO 4892 -2 
Weather 
resistance  c For external installations after exposure to global 
irradiance of 34 GJ/m2 (corresponding to an irradiance 
of 2.3 GJ/m² for the band f rom 300 nm to 400 nm) the 
elongation at break shall be greater than 50 % of the 
initial value.  
For internal installations the 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 fr om 300 nm to 400 nm) shall be greater than 50 % 
of the initial elongation at break.  ISO 4892 -2 
a Test to be carried out on raw material.  
b Test to be carried out on raw material and on tank.  
c Test to be carried out on tank. 
 
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 accordance 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 in ISO 23900 -3.  
8 © UNBS 2020  – All rights  reserved  
 5.4 Catalyst  
The total amount of inorganic material present in polyethylene shall 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 fi ller. 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 weight.  
5.6 Fittings  
It shall be the prerogative of the manufacturer to pr ovide 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 it.  
5.9 Design requirements  
5.9.1  Cylinder shell (unsupported portion of tanks)  
5.9.1.1  The minimum wall thickness es of the tanks  shall be as provided in table s 2, 3, and  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 th e 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 
maximum 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 its own weight 
in an upright position without any external support. The tolerance indic ated 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 in tegrally 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 WDUS 1560: 2020  
© UNBS 2020  – All rights reserved  9 
 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.  
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 t aken 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 3 for blow-moulded  tanks . 
Table 2 — Dimensions of rotational moulded c ylindrical vertical tank  
Volume,  
L Diameter,  
mm Height,  
mm Minimum thickness,  
mm Mass,  
kg 
100 490 710 2.3 3 
150 580 750 2.5 4.5 
250 690 840 2.7 7.0 
500 860 1 040  2.8 11 
750 1 080  1 000  3.0 16.5 
1000  1 080  1 270  3.7 21 
1500  1 260  1 420  3.8 29 
2000  1 380  1 580  4.0 35 
2500  1 480  1 690  4.1 45 
3000  1 580  1 780  4.2 55 
4000  1 760  2 100  4.5 73 
5000  1 850  2 050  4.8 85 
6000  2 520  1 460  5.0 108 
6000  1 980  2 230  5.0 108 
8000  2 190  2 430  6.0 159 
10000  2 850  1 890  10.0 205 
10000  2 380  2 710  10.0 205 
16000  2 900  2 800  15.0 325 
24000  3 560  2 800  18.0 550 
 
Table 3 — Recommended dimensions of rotational moulded rectangular loft tanks  
Volume,  
L Length,  
mm Width,  
mm Height,  
mm Mass,  
Kg  
10 © UNBS 2020  – All rights  reserved  
 250 1 000 700 550 15 
500 1 200 880 620 23 
1 000  1 270 1 270 870 50 
 
Table 4 — Recommended dimensions of 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 
     
1000  2.2 2.5 2.8 16 
1500  2.3 2.8 3.2 24 
2000  2.6 3.0 3.8 32 
2500  2.8 3.0 4.0 40 
3000  3.1 3.4 4.3 48 
4000  3.5 3.7 5.3 64 
5000  3.5 3.9 5.5 80 
8000  3.5 4.0 5.8 130 
10000  4.5 5.0 5.8 170 
 
 
 
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 thickness at each elevation shall be - 10 % of the design thickness on the low side 
and shall be unlimited on the high sid e. The tolerance for individual audit readings shall be limited 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.   WDUS 1560: 2020  
© UNBS 2020  – All rights reserved  11 
 5.11 Mechanical properties  
5.11.1  The flexural modulus of the wall of the water tank shall be not less than 400 N/mm2 when determined 
in accordance with US ISO 120 9-1 and US ISO 1209 -2 
5.11.2  When the cylindrical vertical water storage tank is tested in accordance with Method 1 in Annex C, the 
difference between the circumferential measurements shall be not greater than 2 % of the original 
measurements.  
6 Finish  
6.1 The internal surface of the water storage tank shall be smooth  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 mo uld parting line near the top rim of the tank shall be cut and finished to the required level. 
Defects like air bubbles and pits at the parting line and at the top o f the manhole shall be repaired.  
6.3 The finished tank wall shall be free, as commercially practicable, of visual defects such as foreign 
inclusions, air bubbles, pinholes, pimples, crazing, cracking and delamination  that will impair the serviceability 
of the vessel.  
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 in Annex C. 
7.1.2  When rectangular loft tank is tested in accordance with Method 2 in Annex C, the difference betwe en 
the longitudinal measurements shall be not greater than 3 % of the original measurements.  
7.2 Tensile strength test  
The tensile strength at yield shall be determined in accordance with ISO 18872 . 
7.3 Flexural strength test  
The flexural modulus of the wa ll of the water tank shall be determined in accordance with US ISO 1209 -1 and 
US ISO 1209 -2 
7.4 Hydrostatic pressure head 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 leak age. There shall be no leakage observed. A hydrostatic water test will be conducted if 
ordered by the customer.   
12 © UNBS 2020  – All rights  reserved  
 8 Sampling  
8.1 Lot 
8.1.1  All the water s torage tanks of same raw material, same type, size and produced under relatively 
uniform conditions of manufacture shall constitute a lot.  
8.1.2  The sample size shall be determined in accordance with Table 5 
Table 5 — Scale of sampl ing and criteria for conformity for tanks  
Lot size  Sample size  Maximum permissible failure  
Up to 50  1 0 Failure  
200 2 0 Failure  
300 3 0 Failure  
500 5 0 Failure  
501 and above  8 1 Failure  
8.1.3  Tanks shall be selected at random from the lot. I n 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. WDUS 1560: 2020  
© UNBS 2020  – All rights reserved  13 
 Table 6 — Routine test parameters  
SL No.  Test Clause  
i) Resistance to deformation  7.1 
ii) Hydrostatic pressure head test  7.4 
iii) Carbon black content  Annex A  
iv) Carbon black dispersion  ISO 23900 -3 
8.2 Routine tests  
The routine tests listed in Table 6 shall be carried out to ensure that satis factory quality is maintained during a 
production run.  
9 Marking  
9.1 Plastic water storage tanks shall be marked legibly and indelibly with the following information;  
a) manufacturer's name and address;  
b) net capacity, in litres;  
c) lot number and /or batch number;  
d) country of origin;  
e) manufacture date;  
f) material code; and  
g) recyclable symbol   
14 © UNBS 2020  – All rights  reserved  
 9.2 The method of m arking shall be at the discretion of the 
manufacturer .Annex  A 
(normative)  
 
Determination of c arbon black content  
A.1 Apparatus  
A.1.1  Combustion boat, made of porc elain 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 apparatus as shown in Figure A.1. Both cold 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 in  a fume hood and the two traps following the combustion tube omitted. Fill the dry 
tube with anhydrous CaCl 2 or other suitable desiccant. Hold between loose plugs of glass wool.   WDUS 1560: 2020  
© UNBS 2020  – All rights reserved  15 
 
 
Figure A.1 — Assembly of apparatus for carbon black determination  
A.3.2  Heat a clean combustion boat to red heat 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. I mmediately 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 the rate of nitrogen flow to 1.7 L/min 
±0.3 L/min. Open the inlet e nd 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 boat.  
Insert a copper plug, if this is used.  Quickly close the furnac e 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 maintaining the flow of nitrogen. Remove the copper plug, if present and t he 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 quickly 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 shall be expressed as follows:  
100%
sWrWW 
 
Where; 
W is carbon black content by percent weight  
Wr  is the mass, in grams, of the boat before heating in air;  and 
Ws  is the mass, in grams, of the boat after heating in air   
16 © UNBS 2020  – All rights  reserved  
 Annex  B 
(normative)  
 
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 tank.  
B.2 Method of extraction  
B.2.1 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 specimen at a velocity of 50 mm/s while the speci men is kept fully 
immersed with water. After washing, the 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, and both ends sealed with a 
material that does no t contain any toxic substances nor interfere with the determinations of such constituents 
in the aqueous samples.  
B.2.2 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.  
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 thir d extraction shall be analysed  for lead. The third extraction shall also 
be analysed  for dialkyl tin (C4 and above) as tin.   
B.2.5 When calcium and mercury are present; all three extracts shall be analysed . 
B.3 Method of analysis  
Analysis for lead, tin, ca dmium and mercury shall be carried out using atomic absorption.  WDUS 1560: 2020  
© UNBS 2020  – All rights reserved  17 
 Annex  C 
(normative)  
 
Deformation test  
C.1 Method 1 for cylindrical 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 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 and 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 percentage 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 at the centre of effective height.  
 
Figure C. 1 — Centreline measureme nts 
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 after 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 direction shall be calculated as follows:  
100

12W1L2L
wD
 
Where;   
18 © UNBS 2020  – All rights  reserved  
 D1 is the deformation of the longer side;  
Dw is the deformation of the shorter side;  
W1 is the width at the start of the test;  
W2 is the width at the end of test;  
L1 is the length at the start of the test; and  
L2 is the length at the end of test.  WDUS 1560: 2020  
© UNBS 2020  – All rights reserved  19 
 Bibliography  
[1] US 1560:2013, Rotational moulded polyethylene water storage tank — Specification  
[2] BS EN 13575:2012, Static thermoplastic tanks for the above ground storage of chemicals — Blow 
moulded or rotationally moulded polyethylene tanks — Requirements and test methods  
 WDUS 1560: 2020  
© UNBS 2020 – All rights reserved  21 
 Certifica tion 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 governed by the Standards Act, and the Regulations  made 
thereunder. This mark can be used only by those licensed under the certification mark scheme operated by 
the Uganda National Bureau of Standards and in conjunction with the relevant Uganda Standard. The 
presence of this mark on a product or in relati on 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 product s 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.  
 
 WDUS 1560: 2020    
 
ICS 23.020.10  
Price based on nn pages  
© UNBS 2020 – All rights reserved   
  