consumption across participants is 263 litres per person per day, but there is a large spread in residential water efficiency in different areas. In the 2019 fiscal year, participants reported 119 million cubic meters of water was lost in their water supply systems, equivalent to over 47,000 Olympic-sized swimming pools. This constituted 18% of the 555 million cubic meters of water supplied to the system. Treatment of drinking water Most drinking water supplied through reticulated networks in New Zealand is disinfected using chlorination. However, some communities have water sources derived from deep aquifers that they consider are "secure" or low risk without chlorination. There is opposition to chlorination in some of these communities. However, Water New Zealand, the industry association that represents 1900 water engineers and specialists, advocates for chlorination of all public water supplies. Water supplies in New Zealand generally have low concentrations of naturally-occurring fluoride, at levels that are insufficient to promote good dental health. Fluoridation of public water supplies is undertaken in most public water supplies, typically at a rate between 0.7 and 1.0 mg/L. A report by the Office of the Prime Minister's Chief Science Advisor issued in 2021 confirmed previous studies that showed a positive impact of fluoridation on dental health, and no significant adverse effects. In 2021, the Health (Fluoridation of Drinking Water) Amendment Bill was passed, transferring control over the decision to fluoridate drinking water from local councils to the Director-General of Health. Drinking-water quality Havelock North contamination 2016 From 12 to 29 August 2016 the town of Havelock North experienced New Zealand's largest recorded outbreak of waterborne disease. Campylobacter entered the town's water supply. Of the town's 13,000 residents, 5,500 fell ill, 45 were hospitalised and four died. Inquiry In September 2016, the Government announced an Inquiry into the outbreak, in two stages. Stage 1 focused on identifying what happened, what caused the outbreak, and assessing the conduct of those responsible for providing safe drinking water to Havelock North. Stage 2 of the Inquiry addressed lessons learned for the future and steps to be implemented to reduce the likelihood of such an outbreak occurring again. Findings The drinking water for Havelock North was sourced from an aquifer under the Heretaunga Plains (the Te Mata aquifer) that was thought to be a confined aquifer secure from contaminants. The District Council did not treat water drawn from this aquifer before it was distributed to