Water charges in Canterbury could reach a point where people simply cannot afford to pay, a Selwyn councillor says, as thousands call for the district's pricing system to be reviewed.

An 18 percent water bill hike took effect in July when council-owned organisation Selwyn Water issued its first invoices, a year after the entity was first established.

A petition calling for changes to the pricing structure has attracted 2500 signatures in a matter of days.

Rolleston ratepayer Byron Clarke said the price increase had been a real shock.

"It's a massive rise for anyone to actually deal with at a time when we've got lots of other financial challenges due to the fuel crisis and the knock-on effect on food and so on," he said.

"I can see myself ending up paying over $6000 a year for my rates and the water. That's a massive increase and a real concern for the future."

Selwyn councillor Tracey MacLeod said she understood the frustration and households could only absorb so much.

"I'm a ratepayer here, I live here. My friends and family that live here are also seeing the same stuff," she said.

"I am very aware that rates increases and water increases may well reach a point where we're all looking around going nobody's going to pay this."

MacLeod said the council had already pushed back on the size of the increase, which Selwyn Water initially proposed at 24 percent.

Clarke said ratepayers deserved a clearer explanation of why costs had risen so much, questioning whether they were paying for future development in the fast-growing district.

"It looks like current residents are paying the price for the future and things are not ideal," he said.

"If we can understand why these things have happened, why that massive increase has happened, it might make it a bit more bearable."

Selwyn Mayor Lydia Gliddon said costs were being driven by higher drinking and wastewater standards set by central government, repairing ageing infrastructure and the demands of a growing district.

Gliddon said the council had asked Selwyn Water for a one-year water services strategy so costs, charging arrangements and efficiencies could be examined before longer-term decisions were made.

Selwyn Water deputy chief executive Heather Geddes acknowledged the 18 percent increase had been difficult for some households.

She said some confusion had also resulted from water charges previously included in council rates now appearing on a separate Selwyn Water bill.

"We know [the 18 percent increase] is for a lot of our customers is still a little bit too much to bear and we need to work on that," she said.

Geddes said about 75 percent of the charges passed on to customers related to infrastructure renewals and compliance requirements, while about 23 percent relates to servicing debt.

Selwyn Water was gathering data during its first year to inform future pricing options and planned to consult ratepayers on what constituted fair charges.

"We're really interested in understanding what the community think are fair charges across the district and how we might be able to create different options to make that happen for them," Geddes said.

Selwyn Water and the district council were also working to fix historic water billing issues.

An investigation revealed that council systems failed to capture about 2700 properties between July 2024 and December last year, resulting in up to 2.9 million in unbilled water charges.

A council committee would consider a water billing report on Thursday.