Access to safe drinking-water

This indicator presents statistics on the population who have access to safe drinking-water in Aotearoa New Zealand. 

What is 'safe' drinking-water?

Safe drinking-water is vital for human health. The presence of microbes or chemicals in a drinking-water supply may render that water unsafe to drink. Water that is contaminated with pathogens may cause diseases, particularly gastrointestinal diseases. These waterborne diseases can cause diarrhoea and vomiting. Careful selection of the source and treatment of drinking-water supplies can ensure the water is safe to drink. Registered drinking-water supplies in New Zealand must be regularly tested for microbiological and chemical compliance with the Drinking Water Quality Assurance Rules.

Whether or not a drinking-water supply complies with the Rules is generally based on three measures (Water Services Authority 2025[1]), though in some cases other assessments are used:

• The water supply should be fitted with a means of preventing protozoa such as Cryptosporidium from contaminating it, a ‘protozoa barrier’.
• The supply should feature a means of preventing bacterial contamination (e.g. from coli), referred to as a ‘bacteria barrier’.
• The supply should add a low concentration of a disinfecting agent, such as chlorine, to protect against microbiological contaminants that may remain or enter after the water leaves the treatment facility. This is known as ‘residual disinfection’.

A consumer advisory (eg. a ‘boil-water notice’) may be issued to residents by a supplier if there is a heightened risk that tap water may have microbial contamination, and therefore is not safe to consume. The notice indicates that tap water may not be safe for consumption and must be boiled before use. A temporary notice is issued if there is a short-term heightened risk, as can happen following extreme weather events. A long-term boil-water notice indicates an ongoing heightened risk of microbial contamination.

Information about this indicator

This indicator presents information based on analysis of the supply-level summary dataset for the Drinking Water Regulation Report, published on Water Services Authority – Taumata Arowai’s website, as well as zone-level summary data provided to EHINZ at our request.

The analyses used for this report include all registered supply types, including private community supplies, but exclude 250 single-zone supplies as they lacked associated population data, making them unusable for population analysis.