The Kawerau District Council has put a temporary stop to chlorinating the town water supply, while it looks to solve water discolouration issues.
There has been sporadic yellow to brown discolouration of the town's tap water since chlorination began in July last year.
Chlorine in the water pipes caused staining from natural manganese in the water and dislodged bacterial material which had built up in the system over many years, but the water has been safe to drink.
The council decided to start using chlorine following the Havelock North water contamination in August 2016, which made more than 5000 people sick.
The subsequent Government inquiry report recommended chlorine was the only way to ensure the safety of reticulated drinking water supplies.
Kawerau had previously used UV treatment, which did not provide continuous disinfection of water.
This left the water at risk of being recontaminated by E.coli and other bacteria once it entered the reticulation system.
As a result, Kawerau experienced some low-level E.coli contamination and was not compliant with New Zealand drinking water standards on those occasions.
Council will flush the whole reticulation network and trial cleaning the pipes by air scouring, to resolve the discolouration issue.
It will revisit chlorinating the water supply to meet the drinking water standards, once the discolouration has been solved.
Last week Kawerau mayor Malcolm Campbell said: "The issue is because our water has never been chlorinated before there is a lot of gunk on the pipes that has built up over years".
"The chlorine is stripping it off, which is why it has turned that colour. It is not occurring everywhere, it is sporadic.
"We had the most pristine water in New Zealand, we did not want to have to chlorinate it.
"We were told it could take three to four months for the colour to clear, but it has been much longer and we are not happy about it."