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If a private water supply is to be used as a source of drinking water, it is essential that it complies with The Private Water Supply Regulations for water which is intended for human consumption. Your local authority may insist on testing your supply. The Regulations define a number of “Prescribed Concentrations or Values” (PCVs) relating to a range of chemical and bacteriological parameters.

Drinking Water Standards
Prescribed concentrations or values (maximum unless otherwise stated).
The Water Supply (Water Quality) Regulations 2016

Parameter Unit Concentration or value
Acrylamide µg/litre 0.10
Aluminium µg Al/litre 200
Ammonium mg NH4/litre 0.5
Antimony µg Sb/litre 5
Arsenic µg As/litre 10
Benzene µg/litre 1.0
Benzo(a)pyrene µg/litre 0.010
Boron mg B/litre 1.0
Bromate µgBrO3/litre 10
Cadmium µg Cd/litre 5
Chloride mg Cl/litre 250
Chromium µg Cr/litre 50
Coliforms (faecal) number/100ml 0
Coliforms (total) number/100ml 0
Colony Counts number/ml no significant increase
Colour (filtered) mg/litre Pt scale 20
Conductivity µS/cm 2500 @ 20°C
Copper mg/Cu/litre 2.0
Cyanide µgCN/litre 50
1, 2 dichloroethane µg/litre 3.0
Epichlorohydrin µg/litre 0.10
Faecal streptococci number/100ml 0
Fluoride mg F/litre 1.5
Iron µg Fe/litre 200
Lead µg Pb/litre 10
Manganese µg Mn/litre 50
Mercury µg Hg/litre 1
Nickel µg Ni/litre 20
Nitrate mg NO3/litre 50
Nitrite mg NO2/litre 0.5
Odour dilution number 3 @ 25°C
PAH (Polycyclic Aromatic Hydrocarbons) µg/litre 0.1
Pesticides (total) µg/litre 0.5
pH pH value 6.5 (min) – 10.0 (max)
Selenium µg Se/litre 10
Sodium mg Na/litre 200
Sulphate mg SO4/litre 250
Sulphite reducing clostridia number/100ml 0
Taste dilution number 3 @ 25°c
Tetrachloroethene/Trichloroethene µg/litre 10
Tetrachloromethane µg/litre 3
TOC (Total Organic Carbon) mg C/litre no significant increase
Trihalomethanes µg/litre 100
Tritium (for radioactivity) Bq/litre 100
Turbidity NTU 4
Vinyl Chloride µg/litre 0.5

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