Drinking Water

IS 10500:1991

Characteristics For Drinking Water

Substance or Requirement Undesirable effect Permissible limit
Characteristic in the absence of Remarks
(Desirable Limit) outside the desirable limit alternate source

Essential characteristics Extended to 25 only if toxic
25 substances are not suspected in
1 Colour 5 Above 5, consumer
Hazen Units, Max acceptance decreases absence of alternate source

2 Odour Unobjectioable -- -- a). Test cold and when heatedb).
-- Test at several dilutions
3 Taste Agreeable -- 10 Test to be conducted only after
5 No relaxation safety has been established
4 Turbidity 6.5 to 8.5 Above 5, consumer --
NTU Max acceptance decreases
300 --
5 pH Beyond this range it will
affect mucous membrane
6 Total hardness ( as CaCO3) and water supply system 600 --
mg/L, Max
Encrustation in water supply
structure and adverse effects
on domestic use

7 Iron (as Fe) 0.3 Beyond this limit taste/ 1 --
mg/L, Max appearance are affected, 1000
has adverse effect on -- --
8 Chlorides (as Cl) 250 domestic uses and water To be applicable only when water is
mg/L, Max supply structures, and chlorinated. Tested at consumer
promotes iron bacteria end. When protection against viral
9 Residual, free chlorine 0.2 Beyond this limit, taste, infection is required, it should be
mg/L, Max corrosion and palatability Min 0.5 mg/L.
are affected
--
--
--
Desirable Characteristics
--
10 Dissolved solids 500 Beyond this palatability 2000
mg/L, Max 75 decreases and may cause 200 --
gastro intestinal irritation 1.5
11 Calcium (as Ca) 0.3
mg/L, Max Encrustation in water
supply structure and
12 Copper (asCu) 0.05 adverse effects on domestic
mg/L, Max use

13 Manganese (as Mn) 0.1 A stringent taste, discoloration
mg/L, Max and corrosion of pipes, fitting
and utensils will be caused
beyond this

Beyond this limit taste/
appearance are affected,
has adverse effect on
domestic uses and water
supply structures

14 Sulphate (as SO4) 200 Beyond this causes gastro 400 May be extended upto 400 provided
mg/L, Max intestinal irritation when (as Mg) does not exceed 30
50 magnesium or sodium No relaxation
15 Nitrate (as NO3) 1 are present 1.5 --
mg/L Max 0.001 0.002
0.001 Beyond this methaemo- No relaxation --
16 Fluoride (as F) 0.01 globinemia takes place No relaxation
mg/L, Max 0.01 No relaxation --
0.05 Fluoride may be kept as No relaxation
17 Phenolic compounds 0.05 lowas possible. High fluoride No relaxation To be tested when pollution is
(as C6H5OH) mg/L, Max 0.05 may cause fluorosis No relaxation suspected
Beyond this, it may cause To be tested when pollution is
18 Mercury (as Hg) objectionable taste and colour suspected
mg/L, Max To be tested when pollution is
Beyond this, the water suspected
19 Cadmium (as Cd) becomes toxic
mg/L, Max To be tested when pollution is
Beyond this, the water suspected
20 Selemium (as Se) becomes toxic
mg/L, Max To be tested when pollution is
Beyond this, the water suspected
21 Arsenic (as As) becomes toxic To be tested when pollution is
mg/L, Max suspected
Beyond this, the water
22 Cyanide (as CN) becomes toxic
mg/L, Max
Beyond this, the water
23 Lead (as Pb) becomes toxic
mg/L, Max
Beyond this, the water
becomes toxic

24 Zinc (as Zn) 5 Beyond this limit it can cause 15 To be tested when pollution is
mg/L, Max 0.2 astringent taste and on 1 suspected
0.05 opalescence in water No relaxation
25 Anionic Detergents -- -- To be tested when pollution is
(as MBAS) mg/L, Max Beyond this limit it can suspected
0.01 cause a light froth in water
26 Chromium May be carcinogenic To be tested when pollution is
(as Cr 6+) mg/L, Max above this limit suspected

Polynuclear aromatic May be carcinogenic --
27 hydrocarbons (as PAH)
Beyond this limit undesirable
mg/L, Max taste & odour after
chlorination take place
28 Mineral Oil mg/L, Max 0.03 To be tested when pollution is
Toxic suspected
29 Pesticides mg/L, Max Absent 0.001
-- -- 0.11 --
Radioactive materials 200 600
30 a). Alpha emitters Bq/L, Max 0.03 Beyond this limit taste 0.2 --
1 becomes unpleasant 5
b). Beta emittersBq/L, Max Cumulative effect is reported --
to cause dementia --
31 Alkalinity mg/L, Max --
--
32 Aluminium (as Al)
mg/L, Max

33 Boron, mg/L, Max

Bacteriological Examination

Water in the distribution system

Ideally, all samples taken from the distribution system including consumers’ premises should be free from coliform
organisms. In practice, this is not always attainable, and the following standard of water collected in the
distribution system is therefore recommended when tested in accordance with IS 1622:1981.

a) Throughout any year, 95 percent of samples should not contain any coliform organisms in 100 mL;
b) No sample should contain E. coli in 100 mL;
c) No sample should contain more than 10 coliform organism per 100 mL; and
d) Coliform organism should not be detectable in 100 mL of any two consecutive samples.

Source: Indian standard drinking water - specification (First Revision) IS-10500:1991. BIS, New Delhi, India