An "anti-fluoride" official information request in 2019 was what prompted Wellington Water to investigate the performance of its fluoride plants, emails reveal.
The water company has released hundreds of pages of correspondence under the Local Government Official Information and Meetings Act (LGOIMA), following the region's fluoride failure.
An independent review found water hasn't been fluoridated properly for six years, putting children's oral health at risk.
An email sent in the days after the inquiry was announced earlier this year, a Wellington Water staff member flagged something that "may be of interest".
"What prompted us to investigate the performance of the fluoride plants in more detail was ironically an anti-fluoride OIA (official information) request."
A Wellington Water spokesman clarified the information request was received in October 2019 and sought fluoridation dosing data from drinking water plants.
"In developing the response to the LGOIMA request, we identified inconsistent fluoridation levels and so we commissioned a review of the process," the spokesman said.
It turned out all was not well at the region's fluoridation facilities, as the independent report released last week revealed.
The report said oral health was not a priority within the water company, where staff's main focus was on safe drinking water and ensuring the supply was never overdosed with fluoride.
Fluoride had been administered effectively less than 20 per cent of the time at two treatment plants over six years. It reached a point where the plants became so unreliable both were switched off last year.
Many people were copied into emails about the fact fluoridation had been switched off.
"Although a lot of people knew something needed to be done, people were assuming that someone else was taking responsibility for leading the response," the report said.
The report said emails suggested in October 2021 that the councils should be told about the situation, but there was a reluctance to do this until there was a firm plan in place.
Some of those emails were released by Wellington Water along with the one flagging the "anti-fluoride" request.
They reveal staff were also still deciding in October whether the lack of fluoridation should be escalated to Wellington Water senior leadership.
"I am concerned that this is an expectation and one we have not been meeting at Te Marua since May 2021. In my opinion, yes, I think it should be raised at SLT (senior leadership team)," one person wrote.
In November, the question was raised whether the information had yet been escalated to senior leadership, a staff member replied it was still on the "to-do-list".
By December, one staff member pushed for it to be escalated and offered to help draft something.
"Can I gently suggest, that due to the risk associated with this, that we get it to SLT ASAP?"
Finally, a document outlining the problem was sent to all senior leaders on December 17, although it was not clear two treatment plants had already been switched off.
This led Wellington Water's board to tell the public fluoridation had been switched off at Gear Island and Te Mārua in February 2022.
Days later it emerged this statement was incorrect, which the review said was a result of people "talking past each other".
"However, I am confident there was no deliberate attempt to hide the length of time that fluoride had been turned off at the two plants," the reviewer said.
Wellington Water is working to return fluoridation to the treatment plants by September.