Drinking Water Standards and Guidelines
Revised March 2012

Standards and guidelines for drinking water have evolved over the past 50 years and are continuing to evolve as knowledge increases. Standards are important in providing a basis for judging the safety of water supplies but they are also important in ensuring the acceptability of drinking water, providing a benchmark for water treatment and in some cases a means of reassuring consumers.

There are many influences on standards and not all standards are based on health so care must be taken in interpreting any exceedence of a standard. The most important standards relate to the prevention of waterborne disease caused by pathogens that reach water sources in faecal matter from humans and animals.

Many chemical contaminants can be found in water from natural sources and as a consequence of human activities. Standards for these are mostly based on health, although some are political. WHO in their Guidelines for Drinking Water Quality provide information on a wide range of potential chemical contaminants but it would not be appropriate to simply incorporate all of these into national standards, which should take into account local issues. Standards for chemicals usually incorporate a significant margin of safety and an exceedence of a standard does not necessarily mean that the water is unsafe. Some of these standards also relate to the acceptability of drinking water, particularly in terms of taste, odour or discolouration.

New approaches to assuring drinking water safety and quality are being introduced, particularly Water Safety Plans, which provide a holistic management tool to prevent problems arising.

This Guide explains and explores how standards are derived, taking account of the above considerations.

Copies of this Guide are available from the Foundation, price 15.00, less 20% for FWR Members.

View the full guide