The dam walls of Sydney's main drinking water supply likely to need fixing.

Warragamba Dam may need the remedial work because of engineering issues, according to briefings given to the NSW government.

Ministers have been briefed on the need for possible repairs, Premier Chris Minns said on Tuesday.

"There are geotechnical risks associated with the dam wall which means that Water NSW and the Board of Water NSW may have to take action in relation to remediating the structure from an engineering point of view," Mr Minns said.

"I can confirm I've had briefings from engineers at Water NSW about the next steps and we'll have more to say in the coming days."

It comes after the government staunchly opposed raising Warragamba Dam's wall during the state election campaign, arguing the project had been unfunded by the then Liberal government and could cost between $2b and $3b.

The Liberal-National coalition proposed raising the dam wall by 14m, saying it could prevent 10,000 homes in western Sydney from inundation during a record flood and stop 70,000 needing to be evacuated.

The plan's effectiveness was questioned by Labor, which said close to half of the tributaries responsible for flooding did not flow into the dam and raising the wall would inundate the surrounding National Park and Indigenous World Heritage sites.

"I think it's important, given it was a key issue in the election campaign to reaffirm our opposition to raising the wall by 14m," Mr Minns said.