• to make it safe to drink
• to make it clean by removing particles
• to remove any unpleasant taste or odour

HIGH STANDARDS
The quality of drinking water in Britain is controlled by some of the tightest regulations in the world. The European Community Directive sets standards for over 60 different tests applicable to samples taken. Our own Government regulations are even more stringent.

THE LEGAL REQUIREMENTS

In England and Wales, drinking water standards are set by legislation which includes all EC requirements.

The Water Act 1989 established companies appointed by the Secretary of Sate under licence which can, in some circumstances, be terminated. The Act also covers:

• regulation of prices by a Director General of Water Services
• regulation of quality by a Drinking Water Inspectorate (DWI) and gives
• local authorities some additional responsibilities for checking on drinking water quality

The licenced Companies are obliged by law to supply an adequate and continuous supply of wholesome water.

The 1989 Water Act, now replaced by the Water Industry Act 1991, created a new criminal offence of providing water through pipes which is unfit for human consumption. Proceedings for an offence may only be instituted by the Secretary of State or the Director of Public Prosecutions.

The general obligation to supply wholesome water is supplemented by the Water Quality Regulations, which set out in detail the acceptable levels of certain properties, elements and substances allowed in drinking water.

The Regulations specify the standards against which the quality of water supplied for drinking, washing and cooking purposes is to be assessed. They impose requirements in respect of microbiological parameters, which include faecal coliforms and total coliforms, and also certain physical, chemical and aesthetic parameters. They include EC requirements which are set out in the directive relating to the quality of water intended for human consumption 80/778/EEC, which was approved by the Council of Ministers in July 1980 for implementation five years later in July 1985.

EC LEGISLATION

Maximum admissible concentrations are laid down for 44 of these parameters. Guidance and comments are provided for the other 21 parameters.

The directive enables member states to make derogations in order to take account of situations arising from the nature and structure of the ground and situations arising from exceptional meteorological conditions, provided that such derogations do not relate to toxic or microbiological factors or constitute a public health hazard.

RELAXATIONS
Similarly the Water Quality Regulations enable the Secretary of State for the Environment to authorise a relaxation of their requirements as to wholesomeness where he is satisfied that the authorisation:

• is necessary, ie in an emergency to maintain a water supply
• is called for by reason of exceptional meteorological condition
• is called for by reason of the nature and structure of the ground in the area from which the supply emanates

No relaxations may be authorised if a risk to public health is identified.

UNDERTAKINGS
The Secretary of State is obliged to take enforcement action when standards are not met. However under Section 19 of the 1991 Water Industry Act, he has discretion not to enforce when:

• contraventions are trivial
• water suppliers have given an undertaking to take all necessary steps to secure or facilitate compliance and are complying with the terms of the undertaking

These undertakings contain action programmes setting out what companies intend to do to secure or facilitate compliance and by when.

Such undertakings cannot be accepted, if there is any risk to health from continuing non-compliance. These undertakings have been open to view by the public since September 1989.

TESTING WATER
Water is sampled daily at treatment works, service reservoirs and customers' taps. In addition, the water quality is continuously monitored at treatment works. The works are automatically shut down if set limits are exceeded.

Some 8 million water samples are taken and analysed each year About 99% of the legally required samples meet UK and European Community standards. The few which do not meet the standard fail by a low margin.

Laboratory tests broadly fall into three categories:
physical, chemical and bacteriological.

UNITS OF MEASURE

Results are placed on a public register which customers are welcome to see at water company offices.

The units used in measurement are exceedingly small, for example:

• 1 milligram/litre (mg/l) is 1 part in 1,000,000
• 1 microgram/litre (ug/l) is 1 part in 1,000,000,000
• 1 nanogram/litre (ng/l) is 1 part in 1,000,000,000,000

Many of the measurements we make are actually close to the limits of detection even with the most sophisticated instruments.

WHAT IF A TEST FAILS?

When a sample is analysed and fails a test standard, it does not necessarily mean that the water is unfit to drink Sometimes the failures are caused by the householder's own plumbing system, whilst the water in the mains and in neighbouring properties is good. Even a dirty tap can cause a test failure.

But any failure of the standards is taken seriously. Water companies investigate them thoroughly and, where necessary, do everything possible to cure the trouble.