Local Government Minister Simeon Brown is determined to get to the bottom of Wellington's water issues, which are causing the region to lose more than 40 per cent of its potable water, by demanding answers from its local councils.

Brown wrote an open letter to Wellington Mayor Tory Whanau and Upper Hutt Mayor Wayne Guppy asking both councils about the work done so far to quell the water losses - but this isn't his first attempt to get a clear answer on the matter.

Talking to Summer Breakfast this morning, Brown admitted he'd first tried writing to the Wellington Water Committee before Christmas about the issue, asking what the councils were doing.

He said he received a response from the committee on Thursday which did not include a response from Wellington City Council or Upper Hutt City Council - which didn't help the minister in his goal to uncover what was occurring.

"Therefore, I wrote to them specifically with a range of questions asking what they'd done to address the challenges," he told Summer Breakfast.

"They said they will now be providing me with that information, which is good, but the reality is it's not just about this summer but about future summers.

Brown lamented the 41 per cent of water lost in Wellington and up to 50 per cent, or half, of all water in Upper Hutt being lost - comparing the figures to Auckland's water challenges from back in the day when it was only losing 13 per cent of its water supply.

With Wellington's water restrictions set to kick off last week, Summer Breakfast previously asked the head of regulatory services for Wellington Water, Charles Barker, about the water shortages and what was needed to solve the issue.

Barker had claimed the problem would require a billion dollars a year to fix the infrastructure deficit.

When asked if the money claim was a local or central government issue, Brown said his coalition Government would be aiming to introduce reforms around local water through their strategy called Local Water Done Well.

"[This] will ensure that local councils can form regional council-controlled organisations [CCOs] which are able to be financially sustainable and independent to be able to attract that long-term money," said Brown.

"Wellington Water isn't quite in that league, it relies on the council's budgeting each year to be able to do their work, and so if the council decides not to invest in water, they don't get money from that council to invest in water and that's why I've written to the councils asking what their plans are and what they're doing."

Brown said a CCO that has ring-fenced funding and has revenue sufficiency to borrow and make the necessary investments was the model that the Government would be implementing in order to allow all regional CCOs to be able to do that.

"At the moment, it's up to those councils to make those decisions on a year-to-year basis, and I'm asking what those councils are doing to address those issues," he said.

"We want to see the money paid by ratepayers, whether that's through water charges or rates, going into water rather than into other priorities for the council. We need that ringfenced."

According to Barker, a commonality across all the parties involved with water was their frustration with the quality of infrastructure and the age of the city's pipes and water systems.

Wellington Water would like to see these improved and Barker said the agency would support any reform and changes that would achieve that. He called the infrastructure very old and "historically very underinvested in".

Barker said his team was doing the best it could to navigate the challenges the lack of water and ageing infrastructure presented but understood the frustration around slow progress.

"I can give assurance that the sector is very efficient and effective at using that funding but the councils are under a lot of pressure too," he said on January 12.

"They're doing the best they can to give us the funding we require but everyone knows the different pressures the councils are under."