Operating theatres have been closed at Fiona Stanley Hospital in Perth and ambulances diverted after more flooding at the $2 billion health facility.

It comes after sections of the hospital were flooded in April when a water pipe burst, forcing the closure of eight operating theatres.

That incident led to the cancellation of elective surgery and also affected hot water and air-conditioning systems in the hospital.

Western Australia's Health Minister Kim Hames said he was not sure how many surgeries had been cancelled this time.

"There has been another leak and it looks as though another join has burst; it started in a small room that was for staff but I gather that water is now spreading to other parts, so it's really early days," Dr Hames said.

"We don't know how bad it is but it's certainly a serious leak.

"Some of the theatres have had to close down but other parts of the hospital are being closed as well.

"We only found out an hour or two ago that the leak had occurred...but further info is coming in to say the water is spreading and that is causing further difficulties."

Repairs underway, Fiona Stanley Hospital says

In a statement, Fiona Stanley Hospital described the water leak as large and said the cause had been identified.

"A replacement part has arrived on site and is currently being installed," the statement said.

"The hospital is on ambulance diversion as a precaution.

"There has been no water damage to the operating theatres.

"However, theatre cases have ceased temporarily as a safety measure.

"The hospital anticipates returning to the majority of normal operations by late afternoon."

Labor's health spokesman, Roger Cook, said it was unacceptable for the same problem to happen more than once.

"This is the hospital which was over 12 months late in opening so they could get on top of these issues, but what we see today is more operations cancelled, more patients inconvenienced for simply the same reason that the operating theatres were flooded back on April 19," he said.

"The Minister needs to be answerable for the fact this multi-billion-dollar hospital is simply not functioning properly."

Dr Hames said the flooding was very concerning.

"You'd have to ask why now we've had two sections of pipe burst — areas that are not of any particular note," Dr Hames said.

"The first one was a join, a part that's supposed to last for 100 years, and it burst and you'd think 'oh well, it's a one-off thing'.

"But happening a second time [it] certainly raises concerns, and we'll have to go now presumably to look at all those areas to see if there are other areas that aren't up to scratch.

"These things are meant to last for long periods of time."

The damage bill from the flooding in April remains unclear, along with who will have to pay for it.

Dr Hames said if the leaks were caused by the same problem, it raised serious questions about the quality of the hospital construction.

Earlier this year, the State Government set up an independent review of clinical services at the hospital following a series of highly publicised patient complaints about treatment.

Since the hospital opened, it has been plagued by a number of issues including surgical equipment not being properly sterilised, medical consultants quitting because of excessive workloads, and concerns about the delivery of intravenous drips and other medical supplies to wards.

Concerns about surgical equipment not being properly sterilised prompted the Government to strip private contractor Serco of its sterilisation services contracts at the southern suburbs hospital.

Problems plaguing the hospital are also currently being investigated by a powerful parliamentary committee inquiry.