Reference number  
DRS 189: 2019  
© RSB 2019  
 
 
 RWANDA 
STANDARD  DRS 
189 
 
Second  edition  
2019 -mm-dd 
 
Water quality — Swimming pool — 
Tolerance limits  
 
 
  DRS 189: 2019  
©RSB 2019  - All rights reserved                  ii 
 In order to match with technological development and to keep continuous progress in industries, 
standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition  
 
 
 
 
 
 
 
 
© RSB 2019  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from R SB. 
Requests for permission to reprodu ce this document should be addressed to : 
Rwanda Standards  Board  
P.O Box 7099 Kigali -Rwanda  
KK 15 Rd, 49  
Tel. +250 788303492  
Toll Free: 3250  
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw  
ePortal: www.portal.rsb.gov.rw  DRS 189: 2019  
iii                ©RSB 2019  - All rights reserved  
 Contents  Page 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative references  ................................ ................................ ................................ ...................  1 
3 Requirements  ................................ ................................ ................................ ................................  2 
3.1 Physical requirement s ................................ ................................ ................................ .................  2 
3.2 Chemical requirements  ................................ ................................ ................................ ................  2 
3.3 Bacteriological requirements  ................................ ................................ ................................ ...... 2 
Annex  A (normative)  Determination of standard plate count  ................................ ..............................  3 
A.1 Apparatus  ................................ ................................ ................................ ................................ ...... 3 
A.2 Reagents  ................................ ................................ ................................ ................................ ....... 3 
A.3 Sterilization of apparatus  ................................ ................................ ................................ ............  4 
A.4 Proc edure  ................................ ................................ ................................ ................................ ...... 4 
Annex  B (normative)  Clarity test method  ................................ ................................ ...............................  6 
 DRS 189: 2019  
©RSB 2019  - All rights reserved                  iv 
 Foreword  
Rwanda Standard s are prepared  by Technical Committees and approved by R wanda Standards Board (RSB) 
Board  of Directors in  accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task of technical committees is to prepare national standards.  Final Draft Rwanda S tandards adopted 
by Technical committ ees are ratifie d by me mbers of RSB Board of Director s for publication and gazettment as 
Rwanda Standards.  
RS189 was prepared by Technical Committee RSB/TC 13, Water and sanitation . 
In the preparation of this standard, reference was made to the following standard:  
IS 3328: 1993, Quality tolerances for Water for swimming pools  
The assistance de rived from the above source is hereby acknowledged with thanks.  
This second edition cancels and replaces the first  edition (RS 189:2013 ) which has been technically revised.  
Commit tee membership  
The following organizations were represented on the Technical Committee on Water and Sanitation  (RSB/TC 
13) in the preparation of this standard.  
Ruliba Clays Ltd  
Rwanda Environmental Management Authority (REMA)  
Rwanda Fish Sector (RFS)  
Rwanda Mines, Petroleum and Gas Board (RMB)  
Rwanda Polytechnic/ IPRC -Kigali  
Standards for Sustainability (SFS)  
SULFO Rwanda Ltd  
University of Rwanda/College of Sciences and Technology (UR/CST)  
World Vision Rwanda  
Rwanda  Standards Board  (RSB) – Secretariat  
 DRS 189: 2019  
1                ©RSB 2019  - All rights reserved  
 Water quality  — Swimming  pool  — Tolerance limits  
1 Scope  
This Draft Rwanda Standard  specifies the tolerances limits for the water used in swimming pools of continuous 
circulation type . 
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 
latest edition of the referenced document (including any amendments) applies.  
RS ISO 10523 , Water quality — Determination of pH  
ISO 10566, Water quality — Determination of a luminium — Spectrometric method using pyrocatechol violet 
Water quality -- Determination of suspended solids by filtration through glass -fibre filters  
RS ISO 11923 , Water quality — Determination of suspended solids by filtration through glass -fibre filters  
RS ISO 12020 , Water quality — Determination of aluminium — Atomic absorption spectrometric methods  
ISO 5813, Water quality — Determination of dissolved oxygen — Iodometric method  
ISO 5814 , Water  quality — Determination of dissolved oxygen — Electrochemical probe method  
RS ISO 6332: Water a quality — Determination of iron  
ISO 9963 Water quality — Determination of alkalinity  
RS ISO 7027 , Water quality — Determination of turbidity  
RS ISO 7887 , Water quality — Examination and determination of colour  
ISO 8288 , Water quality — Determination of cobalt, nickel, copper, zinc, cadmium and lead -- Flame atomic 
absorption spectrometric methods  
ISO 9297 , Water quality — Determination of chloride — Silver nitrate titration with chromate indicator (Mohr's  
method)  
ISO 9308 Water quality — Detection and enumeration of Escherichia coli and coliform bacteria — Part 3: 
Miniaturized method (Most Probable Number) for the detection and enumeration of E. coli in surface and waste 
water  
ISO 7393 , Water quality — Determination of free chlorine and total chlorine  
3 Terms and definitions  
No terms and definitions are listed in this document.  
  
©RSB 2019  - All rights reserved                  2 
 4 Requirements  
4.1 Physical requirements  
The water shall be clear, odourless and colourless and shall be sufficiently clear at all times when the pool is in 
use to pass the test  in annex B . 
4.2 Chemical  requirements  
The water shall comply with the chemical tolerances specified in Table 1.  
Table 1  — Chemical tolerances for swimming p ools water 
S/N Characteristic  Tolerance  Test method  
i Total alkalinity (as CaCO 3), mg/l, max.  50 – 500 a ISO 9963  
ii pH,  7.2 – 8.0 a RS ISO 10523  
iii Aluminium (as Al), mg/l, max.  0.1 ISO 10566/ ISO  
12020  
iv Total residual Chlorine, mg/l, range  1.5 – 3.0 ISO 7393  
v Oxygen absorbed in 4 hrs at 27 °C, mg/l, max  1.0 ISO 5813/5814  
vi Total dissolved solids, mg/l, max.  1500  RS ISO 11923  
vii Chloride (as Cl), mg/l, max.  500 RS ISO 9297  
viii Iron, mg/l, max.  0.1 ISO 6232  
ix Heavy metals (as Pb), mg/l, max.  0.1 ISO 8288  
x Colour, Hazen units, max.  10 RS ISO 7887  
xi Turbidity, NTU, max.  10 RS ISO 7027  
a NOTE  Too low alkalinity and low pH are the most common causes of complaints of taste, odour and eye irritation. At 
pH lower than 7.2, there is an increased tendency for formation of di -chloramine and nitrogen chlorides or similar 
compounds which cause eye irritation.  
4.3 Bacteriological requirements  
Table 2 — Limits of m icrobial  contaminants  for swimming pool water  
S/N Characteristic  Limit  Test method  
i Standard plate count, CFU/ml, max.  100 Annex A  
ii Coliform organisms , MPN/100ml, max.  10 ISO 9308 – 3 
 DRS 189: 2019  
3                ©RSB 2019  - All rights reserved  
 Annex  A 
(normative)  
 
Determination of standard plate count  
A.1 Apparatus  
A.1.1  Dilution bottles and tubes  
Bottles or tubes of resistant glass, preferably Pyrex, closed with glass stoppers, rubber stoppers, or screw caps 
equipped  with liners that do not produce toxic or bacteriostatic compounds on sterilization shall be used. Cotton 
plugs shall not be used as closures. Graduation levels shall be indelibly marked on the side of dilution bottle.  
A.1.2  Autoclaves  
Of sufficient size and sha ll keep uniform temperature within the chamber up to and including the sterilizing 
temperature of 121 °C. They shall be equipped with an accurate thermometer located so as to register the 
minimum temperature within the sterilizing chamber, a pressure gauge  and properly adjusted safety valves.  
A.1.3  Pipettes  
1 ml, straight -sided delivery pipettes. The tips shall be unbroken.  
A.1.4  Petri d ishes  
Of 100 mm diameter and 15 mm depth. The bottom of the dishes shall be free from bubbles and scratches and 
shall be flat so that the medium shall be of uniform thickness throughout the plate.  
A.1.5  Incubator  
Maintaining a uniform and constant temperature of 35 ± 0.5 °C at all times in all parts. The use of water -jacketed 
or anhydric type with thermostatically controlled low temperature el ectric heating units and equipped with 
mechanical means of circulating air shall be preferred.  
The incubators shall have sufficient space to accommodate the culture racks and plates, with at least 2.5 cm 
space between adjacent stacks and between walls and stacks.  
They shall be provided with accurate thermometers and a daily record of the temperature shall be maintained.  
A.1.6  Colony Counter  
An approved counting aid, such as Quebee colony counter. If such a counter is not available, then counting 
may be done with a lens giving a magnification of 1.5 diameters. In order to ensure uniformity of conditions 
during counting, illumination equivalent to that produced by Quebee colony counter shall be employed.  
A.2 Reagents  
A.2.1  Buffered  dilution water  
Dissolve 34.0 g of potassium dihydrogen phosphate (KH 2PO 4) in 500 ml of distilled water, adjust to pH 7.2 with 
1 m sodium hydroxide solution and make up to 1 l with distilled water. Add 1.25 ml of the above solution to 1l of 
distilled water. Dispense in amounts that provide 99 ± 2 ml,  or 9.0 ± 0.2 ml, after autoclaving for 20 min.   
©RSB 2019  - All rights reserved                  4 
 A.2.2  Tryptone glucose extract agar medium  
Add 3 g beef extract, 5 g of glucose, and 15 g of agar of each litre of distilled water. Heat to boiling until all 
ingredients are dissolved. Make up lost weight with hot distilled water. Adjust the reaction so that the pH reading 
after sterilization will be between 6.8 and 7.0. Bring to a boiling temperature, stirring vigorously. Make up lost 
weight with hot distilled water and clarify. Distribute to the desired containers  and sterilize in the autoclave at 
121 °C.  
When the pressure reaches zero, remove the medium from the autoclave and cool quickly to avoid 
decomposition to sugars. Store in a container which provides for maintenance of a temperature of 43 °C - 45 °C.  
A.3 Steril ization of apparatus  
A.3.1  Dilution bottles or tubes  
Sterilize the bottles or tubes in the autoclave at 121 °C for 15 min after the temperature reaches 121 °C.  
A.3.2  Petri dishes  
Wrap the petri dishes in Kraft paper and sterilize in the hot air oven at 160 °C for one hour.  
A.3.3  Pipettes  
Place the pipettes in copper, stainless steel or aluminium cylinders with cover or individually wrapped in paper 
and sterilize in the hot -air oven at 160 °C for one hour.  
A.4 Procedure  
A.4.1  Dilution  
Fill the dilution bottles or tubes with proper amou nt of buffered dilution water so that after sterilization they 
contain the desired quantity with a tolerance of 2 %. The exact amount of water to be placed in the bottle may 
be determined only by experiment with the particular autoclave in use. Only buffer ed dilution water is to be used 
for dilution. Tap water or distilled water shall not be used.  
A.4.1.1  Shake the sample bottle vigorously 25 times. Transfer with a sterile pipette 10 ml, 1 ml or 0.1 ml of 
the sample to the proper dilution bottle, tube or petri dish as required. Shake each dilution bottle or tube 
vigorously 25 times after the addition of portion of the sample and before a second dilution or sample is removed.  
A.4.2  Plating  
The amount of the sample taken should be such as will give 30 to 300 colonies on a plate.  
Ordinarily, it is not desirable to plate more than 1 ml of water in a plate; therefore, when the total number of 
colonies developing from 1 ml is less than 30, it is  obviously necessary to record the result as observed, 
disregarding the rule given above. Take 1 ml, 0.1 ml or other appropriate volume of the sample dilution for 
plating in petri dish. Add not less than 10 ml of liquefied tryptone glucose extract agar med ium at a temperature 
of 43 °C - 45 °C to water in the petri dish.  
Flame the lips of all test tubes or flasks used for pouring the medium. Lift the cover of the petri dish just enough 
for the introduction of either pipette or the culture medium. Mix thoroug hly the medium and sample and uniformly 
spread over the bottom of the petri dish by tilting and rotating the dish. Solidify all plates as rapidly as possible 
after pouring and place them immediately in the incubator. Not more than 20 min shall elapse betwe en pouring 
and plating.  DRS 189: 2019  
5                ©RSB 2019  - All rights reserved  
 A.4.3  Incubation  
Incubation shall be done at 35 ± 0.5 °C. Incubate for 24 ± 2 h. Invert the glass covered petri dishes in the 
incubator. Place the dishes in the incubator as prescribed in A.1.5 . 
A.4.4  Counting  
In determining the standard plate count, only such plates should be considered which saw 30 - 300 colonies 
except as provided in A.4.2 . 
Counting shall be done with an approved counting aid. (A.1.6)  
A.4.4.1  If the same amount of water has been planted in 2 or more replicate plates and of th ese, one shows 
colonies within the limits mentioned in A.4.4, while others show less than 30 or more than 300 colonies, the 
results recorded shall be average of all the plates planted with this volume of sample.  
A.4.4.2  In order to avoid fictitious accurac y and yet expense the numerical results by a method consistent 
with the precision of the technique employed, the recorded number of bacterial per millilitre shall be reported as 
follows:  
Up to 100    to the nearest unit  
More than 100   to the nearest 5 units  
Counts shall be designated as the standard plate count at 35 °C.  
  
©RSB 2019  - All rights reserved                  6 
 Annex  B 
(normative)  
 
Clarity test method  
Place a black disc, 150 mm in diameter and fixed to a white background, on the bottom of the pool at the deepest 
point.  
The disc shall be clearly visible from the sidewalks of the pool at all distances up to 9 m in a line drawn across 
the pool through the said disc.  DRS 189: 2019  
ICS 13.060.99  
 
 
©RSB 2019  - All right s reserved