# The Private Water Supplies Regulations 1991, Schedule 2: PRESCRIBED CONCENTRATIONS OR VALUES


Table A
Item
Parameters
Units of Measurement
Concentration or Value (maximum unless otherwise stated)
Note: (i) If silver is used in a water treatment process, 80 may be substituted for 10.
1.
Colour
mg/1 Pt/Co scale
20
2.
Turbidity (including suspended solids)
Formazin turbidity units
4
3.
Odour (including hydrogen sulphide)
Dilution number
3 at 25°C
4.
Taste
Dilution number
3 at 25°C
5.
Temperature
°C
25
6.
Hydrogen ion
pH value
9.5
5.5 (minimum)
7.
Sulphate
mg SO4/1
250
8.
Magnesium
mg Mg/1
50
9.
Sodium
mg Na/1
150
10.
Potassium
mg K/1
12
11.
Dry residues
mg/1
1500 (after drying at 180°C)
12.
Nitrate
mg NO3/1
50
13.
Nitrite
mg NO2/1
0.1
14.
Ammonium (ammonia and ammonium ions)
mg NH4/1
0.5
15.
Kjeldahl nitrogen
mg N/1
1
16.
Oxidisability (permanganate value)
mg O2/1
5
17.
Total organic carbon
mg C/1
No significant increase over that normally observed
18.
Dissolved or emulsified hydrocarbons (after extraction with petroleum ether); mineral oils
μg/1
10
19.
Phenols
μg C6H5OH/1
0.5
20.
Surfactants
μg/1 (as lauryl sulphate)
200
21.
Aluminium
μg Al/1
200
22.
Iron
μg Fe/1
200
23.
Manganese
μg Mn/1
50
24.
Copper
μg Cu/1
3000
25.
Zinc
μg Zn/1
5000
26.
Phosphorus
μg P/1
2200
27.
Fluoride
μg F/1
1500
28.
Silver
μg Ag/1
10(i)
Table B
Item
Parameters
Units of Measurement
Maximum Concentration
Note:
(i) The sum of the detected concentrations of individual substances.
(ii) The sum of the detected concentrations of fluoranthene, benzo 3.4 fluoranthene, benzo 11.12 fluoranthene, benzo 3.4 pyrene, benzo 1.12 perylene and indeno (1,2,3-cd) pyrene.
1.
Arsenic
μg As/1
50
2.
Cadmium
μg Cd/1
5
3.
Cyanide
μg CN/1
50
4.
Chromium
μg Cr/1
50
5.
Mercury
μg Hg/1
1
6.
Nickel
μg Ni/1
50
7.
Lead
μg Pb/1
50
8.
Antimony
μg Sb/1
10
9.
Selenium
μg Se/1
10
10.
Pesticides and related products:
(a) individual substances
μg/1
0.1
(b) total substances(i)
μg/1
0.5
11.
Polycyclic aromatic hydrocarbons(ii)
μg/1
0.2
Table C
Item
Parameters
Units of Measurement
Maximum Concentration
Note: (i) Analysis by multiple tube method.
1.
Total coliforms
number/100 ml
0
2.
Faccal coliforms
number/100 ml
0
3.
Faccal streptococci
number/100 ml
0
4.
Sulphite-reducing clostridia
number/20 ml
≤1(i)
5.
Colony counts
number/1 ml at 22°C or 37°C
No significant increase over that normally observed
Table D(i)
Item
Parameters
Units of Measurement
Maximum Concentration or Value
Note: (i) See regulation 3(3)(d).
1.
Conductivity
μS/cm
1500 at 20°C
2.
Chloride
mg Cl/1
400
3.
Calcium
mg Ca/1
250
4.
Substances extractable in chloroform
mg/1 dry residue
1
5.
Boron
μg B/1
2000
6.
Barium
μg Ba/1
1000
7.
Benzo 3,4 pyrene
μg/1
10
8.
Tetrachloromethane
μg/1
3
9.
Trichloroethene
μg/1
30
10.
Tetrachlorothene
μg/1
10
Table E
Item
Parameters
Units of Measurement
Minimum Concentration(i)
Note: (i) See regulation 3(4).
1.
Total hardness
mg Ca/1
60
2.
Alkalinity
mg HCO3/1
30

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Source: https://www.legislation.gov.uk/uksi/1991/2790/schedule/2 (the official version)
Page: https://openlegislation.uk/private-water-supplies-regulations-1991/schedule-2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.