The World Health Organization, 2021 estimate around 829 000 people die each year from diarrhoea as a result of unsafe drinking-water, sanitation, and hand hygiene. The quality of water, whether used for drinking, agriculture or recreational purposes, is significant for health in all populations.

In Wales, water companies supply drinking water that is safe and meets relevant water quality standards. Water not supplied by water companies – a ‘private’ supply – is also monitored and assessed against drinking water standards to ensure its quality. About 80,000 people in Wales have a private water supply (Public Health Wales, 2021). Occasionally, elevated levels of harmful chemicals may be present in water, from natural sources, agricultural or industrial activities, or following accidental release. Consuming water that has been contaminated has the potential to lead to ill-health both in the short and long term. Drinking water may also be responsible for the spread of infectious diseases if biologically contaminated.