Drinking Water Standards and Regulations

What are the drinking water standards?

Drinking water must be ‘wholesome’ and this is defined in law mainly by setting standards for a wide range of substances, organisms and properties of water in regulations. There is an additional requirement to make sure that it does not contain anything else that might be a potential danger to human health, as identified by risk assessment. The standards are set to be protective of public health and the definition of wholesome includes factors that might affect the look, smell or taste of the water which needs to be acceptable to consumers. There is good agreement amongst experts worldwide on the science behind the setting of health based standards for drinking water and this expert evidence is documented by the World Health Organisation in the Guidelines for Drinking Water Quality. You can look up all the background information to standards of water safety here: Guidelines for drinking-water quality: Fourth edition incorporating the first and second addenda (who.int). The legal standards in the UK were based on those which were set in Europe in the Drinking Water Directive 1998 and subsequent revisions, together with national standards set to maintain the high quality of water already achieved. The standards are strict and include wide safety margins. They cover:

• micro-organisms

• chemicals such as nitrate and pesticides

• metals such as lead and copper

• the way water looks and how it tastes

The full regulations can be found The Water Supply (Water Quality) Regulations 2016 (legislation.gov.uk). An explanation of the organisms and substances tested for regularly can be found in the Chief Inspector’s Report. This guide also explains how drinking water is regulated in England and Wales.

Terms Explained

Parameter: Substance or organism tested for routinely in drinking water.

Directive requirements: These are the standards and specifications set in the EU Drinking Water Directive and were adopted into national legislation.

National requirements: These are national standards and specifications in the regulations which apply only in the England and Wales.

Concentration or value or specification: Maximum or minimum or range allowed in drinking water.

Point of compliance: The point where the legal standards apply, normally this is the consumers tap but it may be at the water works.

µg/l: Micrograms per litre (parts per billion).

mg/l: Milligrams per litre (parts per million).

Microbiological Parameters

Parameters	Concentration or Value maximum)	Units of Measurement	Point of compliance
Enterococci	0	number/100ml	Consumers’ taps
Escherichia coli (E. coli)	0	number/100ml	Consumers’ taps

Table 1: Part I – Directive requirements

Parameters	Concentration or Value maximum)	Units of Measurement	Point of compliance
Coliform bacteria	0	number/100ml	Service reservoirs* and water treatment works
Escherichia coli (E. coli)	0	number/100ml	Service reservoirs and water treatment works

Table 2: Part II – National requirements

Note: *Compliance required as to 95% of samples from each service reservoir

Chemical Parameters

Parameters	Concentration or Value maximum)	Units of Measurement	Point of compliance
Acrylamide	0.10	µg/l	(i)
Antimony	5.0	µgSb/l	Consumers’ taps
Arsenic	10	µgAs/l	Consumers’ taps
Benzene	1.0	µg/l	Consumers’ taps
Benzo(a)pyrene	0.010	µg/l	Consumers’ taps
Boron	1.0	mgB/l	Consumers’ taps
Bromate	10	µgBrO3/l	Consumers’ taps
Cadmium	5.0	µgCd/l	Consumers’ taps
Chromium	50	µgCr/l	Consumers’ taps
Copper(ii)	2.0	mgCu/l	Consumers’ taps
Cyanide	50	µgCN/l	Consumers’ taps
1, 2 dichloroethane	3.0	µg/l	Consumers’ taps
Epichlorohydrin	0.10	µg/l	(i)
Fluoride	1.5	mgF/l	Consumers’ taps
Lead (ii)	10	µgPb/l	Consumers’ taps
Mercury	1.0	µgHg/l	Consumers’ taps
Nickel (ii)	20	µgNi/l	Consumers’ taps
Nitrate (iii)	50	mgNO3/l	Consumers’ taps
Nitrite (iii)	0.50	mgNO2/l	Consumers’ taps
	0.10		Treatment works
Pesticides (iv)(v)
Aldrin	0.030	µg/l	Consumers’ taps
Dieldrin	0.030	µg/l	Consumers’ taps
Heptachlor	0.030	µg/l	Consumers’ taps
Heptachlor epoxide	0.030	µg/l	Consumers’ taps
other pesticides	0.10	µg/l	Consumers’ taps
Pesticides: Total (vi)	0.50	µg/l	Consumers’ taps
Polycyclic aromatic hydrocarbons (vii)	0.10	µg/l	Consumers’ taps
Selenium	10	µgSe/l	Consumers’ taps
Tetrachloroethene and Trichloroethene (viii)	10	µg/l	Consumers’ taps
Trihalomethanes: Total (ix)	100	µg/l	Consumers’ taps
Vinyl chloride	0.50	µg/l	(i)

Table 3: Part I – Directive requirements

Notes:

1. The parametric value refers to the residual monomer concentration in the water as calculated according to specifications of the maximum release from the corresponding polymer in contact with the water. This is controlled by product specification.
2. See also regulation 6(6)
3. See also regulation 4(2)(d)
4. See the definition of “pesticides and related products” in regulation 2
5. The parametric value applies to each individual pesticide.
6. “Pesticides: Total” means the sum of the concentrations of the individual pesticides detected and quantified in the monitoring procedure.
   The specified compounds are:

 – benzo(b)fluoranthene
 – benzo(k)fluoranthene
 – benzo(ghi)perylene
 – indeno(1,2,3-cd)pyrene.

1. The parametric value applies to the sum of the concentrations of the individual compounds detected and quantified in the monitoring process.

The parametric value applies to the sum of the concentrations of the individual compounds detected and quantified in the monitoring process.

1. The specified compounds are:

 – chloroform
 – bromoform
 – dibromochloromethane
 – bromodichloromethane.

The parametric value applies to the sum of the concentrations of the individual compounds detected and quantified in the monitoring process.

National Requirements

Parameters	Concentration or Value (maximum unless otherwise stated)	Units of Measurement	Point of compliance
Aluminium	200	µgAl/l	Consumers’ taps
Colour	20	mg/l Pt/Co	Consumers’ taps
Iron	200	µgFe/l	Consumers’ taps
Manganese	50	µgMn/l	Consumers’ taps
Odour	Acceptable to consumers and no abnormal change		Consumers’ taps
Sodium	200	mgNa/l	Consumers’ taps
Taste	Acceptable to consumers and no abnormal change		Consumers’ taps
Tetrachloromethane	3	µg/l	Consumers’ taps
Turbidity	4	NTU	Consumers’ taps

Table 4: National requirements