Officials have admitted lead contamination is not the only major problem at the Perth Children’s Hospital yet to be fixed.

A raft of issues have been outlined at a budget estimates committee hearing by WA Child and Adolescent Health Service head Robyn Lawrence, including problems at the onsite childcare facility, mental health unit, isolation rooms and anaesthetic gas delivery.

“The childcare centre and the surrounds around it are incomplete, there's issues in the kitchen still to be resolved,” she said.

“Within the mental health unit there are requirements for safety and the enclosure of balconies and balustrading that need to be dealt with.”

Ms Lawrence said there were problems with the function of the isolation rooms and anaesthetic gas equipment.

“Whilst some of these do have dates for conclusion, not all of them and one of the biggest ones ... the brains of the building management system and the integration with the clinical systems such as nurse call bell and the security systems, remain to be completed,” she said.

The works are the responsibility of head contractor John Holland.

The $1.2 billion project is over two years behind schedule, and will not open until 2018.

The best-known issue is lead contamination in the drinking water, which remains unresolved.

WA Health director-general David Russell-Weisz has defended the Government's decision to accept John Holland’s claim that the hospital had been completed.

“We ... knew at the time then that we would take practical completion with a number of defects listed at practical completion,” Dr Russell-Weisz said.

“The most significant issue here, or advantage, was we got control.

“There is not a parallel universe we could go on if we hadn't, but on how the builder has operated to date, I would imagine we would be in a much worse situation than we are now.”

The WA Government is soon expected to announce when the hospital will open.

Reports say a legal battle between the state and John Holland is increasingly likely too.