ICS 81.060.20  
 
Reference number
DRS 561: 2023
© RSB2023
  
 RWANDA 
STANDARD  DRS 
561 
 
First edition  
2023-mm-dd 
 
Ceramic water filters — Specification 
   
DRS 561: 2023 
©RSB 2023 - 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 2023 
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 RSB. 
Requests for permission to reproduce 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 561: 2023 
iii                ©RSB 2023 - All rights reserved 
 Contents  
Foreword ............................................................................................................................................................ iv  
1 Scope ...................................................................................................................................................... 1  
2 Normative references ............................................................................................................................ 1  
3 Terms and definitions ........................................................................................................................... 2  
4 Material ................................................................................................................................................... 3  
5 Requirements ......................................................................................................................................... 3  
5.1 General requirements ........................................................................................................................... 3  
5.2 Specific requirements ........................................................................................................................... 3  
6 Packaging ............................................................................................................................................... 5  
7 Labelling ................................................................................................................................................. 5  
8 Sampling ................................................................................................................................................ 5  
Annex A (normative)  Detection of internal cracks ......................................................................................... 6  
A.1 Principle ................................................................................................................................................. 6  
A.2 Procedure ............................................................................................................................................... 6  
Annex B (normative)  Determination of rate of filtration ................................................................................ 7  
B.1 B.1 Apparatus ........................................................................................................................................ 7  
B.2 B.2 Procedure ........................................................................................................................................ 7  
Annex C Annex C (normative)  Test for presence of silver ............................................................................ 8  
C.1 Preparation of the sample .................................................................................................................... 8  
C.2 Reagents ................................................................................................................................................ 8  
C.3 Procedure ............................................................................................................................................... 8  
Annex D Annex D (normative)  Sampling and criteria for conformity .......................................................... 9  
D.1 Lot ........................................................................................................................................................... 9  
D.2 Scale of sampling and criteria for conformity .................................................................................... 9  
D.2.1 General ................................................................................................................................................... 9  
D.2.2 Detection of internal cracks ................................................................................................................. 9  
D.2.3 Tests for rate of filtration, presence of silver and all parameters in Table 2 .................................. 9  
 DRS 561: 2023 
©RSB 2023 - All rights reserved                  iv 
 Foreword 
Rwanda Standardsarepreparedby Technical Committees and approved by Rwanda 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 Standards 
adopted by Technical committees are ratified by members of RSB Board of Directors for publication and 
gazettment as Rwanda Standards. 
DRS561 was prepared by Technical Committee RSB/TC 48, Plastic tanks, pipes, accessories and related 
products.  
In the preparation of this standard, reference was made to the following standard: 
FDUS 2662: 2023, Ceramic water filters — Specifications  
The assistance derived from the above source is hereby acknowledged with thanks. 
Committee membership  
The following organizations were represented on the Technical Committee on Plastic tanks, pipes, 
accessories and related products, (RSB/TC 48) in the preparation of this standard. 
Entreprise URWIBUSTO 
Kigali Water Limited/METITO 
MILTEC 
ROTO Ltd 
Prowater Ltd 
RWACOM industry 
Rwanda Plastic Industry 
Rwanda Water Board (RWB) 
SPOUTS OF WATER 
Water Sanitation Corporation WASAC DRS 561: 2023 
v                ©RSB 2023 - All rights reserved 
 Rwanda Standards Board(RSB) – Secretariat DRS 561: 2023 
1                ©RSB 2023 - All rights reserved 
 Ceramic water filters — Specification 
1 Scope 
This Draft Rwanda standard specifies requirements, sampling and test methods for ceramic water filter used 
to filter water for human consumption. 
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 editioncited applies. For undated references, 
the latest edition of the referenced document (including any amendments) applies. 
ASTM D3866-18, Standard Test Methods for Silver in Water 
RS ISO 9308-1, Water quality — Enumeration of Escherichia coli and coliform bacteria — Part 1: Membrane 
filtration method for waters with low bacterial background flora 
RS ISO 11923, Water quality — Determination of suspended solids by filtration through glass-fibre filters 
RS ISO 15681-2, Water quality — Determination of orthophosphate and total phosphorus contents by flow 
analysis (FIA and CFA) — Part 2: Method by continuous flow analysis (CFA) 
RS ISO 17378-2, Water quality — Determination of arsenic and antimony — Part 2: Method using hydride 
generation atomic absorption spectrometry (HG-AAS) 
RS ISO 15681- 2, Water quality — Determination of orthophosphate and total phosphorus contents by flow 
analysis (FIA and CFA) 
RS ISO 4832, Microbiology of food and animal feeding stuffs — Horizontal method for the enumeration of 
coliforms — Colony-count technique  
RS ISO 5961, Water quality — Determination of cadmium by atomic absorption spectrometry  
RS ISO 6222, Water quality — Enumeration of culturable microorganisms — Colony count by inoculation in 
nutrient agar culture media  
RS ISO 6333, Water quality — Determination of manganese — Formaldoxime spectrometric method  
RS ISO 6461-2, Water quality — Detection and enumeration of the spores of sulfite-reducing anaerobes 
(clostridia) — Part 2: Method by membrane filtration  
RS ISO 6777, Water quality — Determination of nitrite — Molecular absorption spectrometric method   
©RSB 2023 - All rights reserved                  2 
 ISO 6785, Milk and milk products — Detection of Salmonella spp.  
RS ISO 6888-1, Microbiology of food and animal feeding stuffs — Horizontal method for the enumeration of 
coagulass-positive staphylococci (Staphylococcus aureus and other species) 
RS ISO 7027-1, Water quality — Determination of turbidity — Part 1: Quantitative methods 
RS ISO 7887, Water quality — Examination and determination of colour  
RS ISO 7888, Water quality — Determination of electrical conductivity  
RS ISO 7890-3, Water quality — Determination of nitrate — Part 3: Spectrometric method using sulfosalicylic 
acid 
RS ISO 7899-2, Water quality — Detection and enumeration of intestinal enterococci — Part 2: Membrane 
filtration method 
RS ISO 8288, Water quality — Determination of cobalt, nickel, copper, zinc, cadmium and lead — Flame 
atomic absorption spectrometric methods  
ISO 10359-2, Water quality — Determination of fluoride — Part 2: Determination of inorganically bound total 
fluoride after digestion and distillation  
RS ISO 10523, Water quality — Determination of pH  
RS ISO 12846, Water quality — Determination of mercury — Method using Atomic Absorption Spectrometry 
(AAS) with and without enrichment 
RS ISO 16266-2, Water quality — Detection and enumeration of Pseudomonas aeruginosa — Part 2: 
Membrane filtration method  
RS ISO 17378-2, Water quality — Determination of arsenic and antimony — Part 2: Method using hydride 
generation atomic absorption spectrometry (HG-AAS)  
RS ISO 21567, Microbiology of food and animal feeding stuffs — Horizontal method for the detection of 
Shigella spp.  
3 Terms and definitions 
For the purposes of this standard, the following terms and definitions apply  
3.1  
ceramic 
brittle, corrosion and heat resistant, inorganic non-metallic material produced by high-temperature processing DRS 561: 2023 
3                ©RSB 2023 - All rights reserved 
 3.2  
firing 
controlled heat treatment of ceramic ware in a kiln or furnace, during the process of manufacture, to develop 
the desired properties 
3.3  
unglazed 
hard, dense material of homogeneous composition, deriving colour and texture from materials of which the 
body is made 
4 Material 
4.1 The ceramic water filter shall be fired, unglazed porous ware and subsequently, suitably treated 
chemically so that fine silver is embedded in the body of the filter. 
4.2 The manufacturer shall provide a suitablefood grade material for cleaning the ceramic water filter. 
5 Requirements 
5.1 General requirements 
The ceramic water filter shall: 
a) be properly fired so as not to shed particles under conditions of normal use; 
b) be free from cavities, warpage, uneven firing and protrusion; and 
c) not haveany cracks. 
d) not have carbon traces 
 
5.2 Specific requirements 
5.2.1 The ceramic water filter shall comply with the specific requirements given in Table 1 when tested in 
accordance with the test methods specified therein. 
Table 1 — Specific requirements for ceramic water filter 
S/N Parameter Requirement Test method 
i Detection of internal cracks To pass test  Annex A 
ii Rate of filtration, l/hr To pass test Annex B 
iii Presence of silver To pass test Annex C  
©RSB 2023 - All rights reserved                  4 
 5.2.2 Plastic receptacles that are used with ceramic water filter shall conform to FDEA 1080. receptacles other than 
from plastic product shall meet relevant requirements.    
5.2.2 The ceramic water filter shall comply with the performance requirements given in Table 2 when the 
filtrate is tested in accordance with the test methods specified therein. 
Table 2 — Performance requirements for the filtrate 
S/N Parameter Requirement Test method 
i.  Suspended matter Not detectable ISO 11923 
ii.  pH  6.5 – 8.5 ISO 10523 
iii.  Conductivity, µS/cm, max. 1 500 ISO 7888 
iv.  Colour, TCU, max. 15 ISO 7887 
v.  Turbidity, NTU, max. 5 ISO 7027-1  
vi.  Silver, mg/L, max. 0.1 ASTM D3866-18 
vii.  Arsenic, mg/L, as As, max. 0.01 ISO 17378-2 
viii.  Cadmium, mg/L, as Cd, max. 0.003 ISO 5961 
ix.  Lead, mg/L, as Pb, max. 0.01 
ISO 8288 
x.  Copper, mg/L, as Cu, max. 1.000 
xi.  Mercury (total as Hg), mg/L, max. 0.001 ISO 12846 
xii.  Manganese, mg/L, as Mn, max. 0.1 ISO 6333 
xiii.  Nickel, mg/L, as Ni, max. 0.02 ISO 8288 
xiv.  Nitrate as NO 3-,mg/L, max. 45 ISO 7890-3 
xv.  Nitrite, mg/L, max. 0.003 ISO 6777 
xvi.  Phosphates, mg/L, as PO 43-, max. 2.2 ISO 15681-2 
xvii.  Fluoride, mg/L, as F, max. 1.5 ISO 10359-2 
xviii.  Escherichia coli , in 100 ml Absent ISO 9308-1 
ISO 4832 xix.  Total coliforms, in 100 ml Absent 
xx.  Total viable counts at 22 ºC, ml, max.a) 100 
ISO 6222  
xxi.  Total viable counts at 37 ºC, ml, max. a) 50 
xxii.  Staphylococcus aureus in 100 ml  Absent ISO 6888-1  
xxiii.  Sulphite reducing anaerobes in100 ml  Absent ISO 6461-2  
xxiv.  Pseudomonas aeruginos a fluorescence in 100 ml  Absent ISO 16266-2 
xxv.  Streptococcus faecalis in 100 ml  Absent ISO 7899-2  
xxvi.  Shigella spp. in 100 ml  absent ISO 21567  
xxvii.  Salmonella spp. in 100 ml  Absent ISO 6785  
aThis parameter is for monitoring the system at source. Total time before analysis should be not more than 6 h at 4 
ºC. Determination of total viable counts shall start within 12 h after collection of the potable water sample.  
 DRS 561: 2023 
5                ©RSB 2023 - All rights reserved 
 6 Packaging 
The ceramic water filters and its components shall be packaged in suitable packaging material that ensure the 
product’s integrity. 
7 Labelling 
7.1 The ceramic water filter shall be legibly and indelibly labelled with the following information: 
a) manufacturer’s name and recognized trademark, if any; 
b) rate of filtration, in litres per hour (L/hr); 
c) capacity of filtering element in litres; 
d) lot/batch number; 
e) country of origin; and  
f) physical address of the manufacturer. 
7.2 The manufacturer shall provide an information leaflet with the following information: 
a) “Clean the ceramic water filter every 7days or when clogged”; 
b) “Scrub the ceramic water filter with clean water and a suitable food grade material, as provided by the 
manufacturer. DO NOT use soap to clean the filter pot”; 
c) “Wash the bucket, tap and lid with clean water and soap”; and 
d) “Replace the ceramic water filter after two (2) years of use or when the filtration rate is reduced”. 
8  Sampling 
The sampling procedure and the criteria for conformity shall be as given in Annex D.  
©RSB 2023 - All rights reserved                  6 
 Annex A 
(normative)  
 
Detection of internal cracks 
A.1 Principle 
This test is to detect internal cracks on the filter element. 
A.2 Procedure 
A.2.1 Submerge a filtering element in water only up to its rim, without letting water flow into the filter. 
A.2.2 Hold It for about 10 s to see if any water seeps through the walls of the filter. 
A.2.3 If water seeps through the walls of the filter after being submerged for the 10 s, it is an indication of 
internal cracks and the filter has failed this test. 
  DRS 561: 2023 
7                ©RSB 2023 - All rights reserved Annex B 
(normative)  
 
Determination of rate of filtration 
B.1 B.1 Apparatus 
B.1.1 Calibrated T-Device  to measure the change in water level 
B.1.2 Stop watch  
B.2 B.2 Procedure 
B.2.1 Soak the filtering element for 24 hin a pool of water. 
B.2.2 The soaked filter pots are removed from the pool and laid on a raised platform (racks). 
B.2.3 Fill up the pot with clean water to full capacity. 
B.2.4 A stopwatch is set for 1 h. 
B.2.5 After 1 h of filtration, the water level in litres per hour is read from the calibrated T-Device. 
B.2.6 The acceptable rate of filtration shall be as declared by the manufacturer. 
NOTE See Figure B.1. 
 
Figure B.1— Setup for determination of the rate of filtration 
 
©RSB 2023 - All rights reserved                  8 
 Annex CAnnex C 
(normative) 
 
Test for presence of silver 
C.1 Preparation of the sample 
Break the ceramic water filter, take sufficient quantity of pieces in agitated pestle and mortar and grind to fine 
powder to give more than 5 g of powder. 
C.2 Reagents 
C.2.1 Dilute nitric acid,  50 %, (v/v) 
C.2.2 Dilute hydrochloric acid  35 %, (v/v) 
C.2.3 Liquor ammonia  
C.3 Procedure 
C.3.1 Take 5 g of finely agated ceramic water filter material, wash with distilled water, allow the mixture to 
settle and decant the supernatant and wash out at least thrice. Decant the supernatant liquid. 
C.3.2 Digest the residue with 50 ml of dilute nitric acid on a hot plate and allow settling.  
C.3.3 Decant the supernatant liquid into a suitable glass tube.  
C.3.4 Add into the glass tube a few mills of dilute hydrochloric acid.  
C.3.5 If the solution shows white turbidity, confirm presence of silver by adding an excess of liquid 
ammonia, when the turbidity disappears. 
 
 
 
 
 
 DRS 561: 2023 
9                ©RSB 2023 - All rights reserved 
 Annex D 
(normative) 
 
Sampling and criteria for conformity 
D.1 Lot 
D.1.1 In a consignment all the ceramic water filters, manufactured from the same type of material and 
belonging to the same batch of manufacture shall be grouped together to constitute a lot.  
D.1.2 Each lot shall be tested for conformity to the requirements of this standard. 
D.2 Scale of sampling and criteria for conformity 
D.2.1 General 
D.2.1.1 The number of ceramic water filters to be sampled from each lot depends on the size of the lot 
and shall be as given in Table D.1. 
D.2.1.2 The ceramic water filters shall be selected at random making use of random number tables. 
D.2.2 Detection of internal cracks 
D.2.2.1 The number of ceramic water filters to be sampled for examining the above parameter is given in 
Column 3 of Table D.1. 
D.2.2.2 Any ceramic water filter failing in one or more of the tests shall be termed defective. 
D.2.2.3 The number of defective ceramic water filters shall not exceed the acceptance number in Column 
4 of Table D.1, if the lot is to be accepted.  
D.2.3 Tests for rate of filtration, presence of silver and all parameters in Table2 
D.2.3.1 The number of tests to be conducted for each of the above parameters is given in Column 5 of 
Table D.1. 
D.2.3.2 For conducting these tests, sample test pieces shall be obtained from the sample ceramic water 
filters as described in the respective test methods. 
D.2.3.3 No failures shall occur, if the lot is to be declared satisfactory.  
©RSB 2023 - All rights reserved                  10 
 Table D.1 — Scale of sampling and criteria for conformity 
S/N Lot size Sample size 
for detection 
of cracks Acceptance 
number Number of tests for rate of 
filtration, presence of silver and  
all parameters for Table 2 and 
Table D.1 
i.  Up to 25 3 0 1 
ii.  26 to 50 5 0 1 
iii.  51 to 100 8 1 2 
iv.  101 to 200 13 1 3 
v.  201 and above 20 2 4 
 DRS 561: 2023 
 
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