Twenty-seven councils have been given until June 30th, 2024 to produce funded plans for installing protozoa barriers on water supplies.
Without them, hundreds of thousands of New Zealanders could be at risk of bugs such as cryptosporidium.
Christchurch City Council has the biggest potential impact - with more than 168,000 residents relying on two non-compliant supplies.
The Council declined RNZ's interview requests, as did Waimakariri and Taupō councils, which could affect 29,000 and 8000 people respectively.
Taumata Arowai head of regulatory Steve Taylor spoke to Guyon Espiner.
