Hard-hitting changes for New Zealand's drinking water are expected in the coming days.

That's the message from Water New Zealand, ahead of the release of the final report of the Havelock North water contamination inquiry.

The Attorney General will release the report in the next few days.

It will focus on systemic failures in the country's drinking water sector which contributed to the 2016 water contamination crisis.

The campylobacter outbreak struck down more than five-thousand people with gastro, hospitalised 45 and has been linked to three deaths.

Water New Zealand's principal advisor on water quality Jim Graham said he's expecting the inquiry panel to want all drinking water in New Zealand to be permanently treated.

"Water suppliers would either have to accept treatment, or they'd have to considerably upgrade the way they provide water if it's not treated."

Graham said big changes need to happen to the Drinking Water Assessors role.

"Some of our Drinking Water Assessors work part time, are severely under resourced, they are over worked, they work under a lot of pressure."