The Australian Nursing Federation (ANF) says it will support its members who refuse to move to the Perth Children's Hospital until an independent third party confirms lead contamination has been eradicated.

The Government and the head contractor, John Holland, have been unable to agree on the source of the contamination.

John Holland said the water being delivered to the building was contaminated, but the WA Chief Public Health Officer disputed that.

The Government said it would not take ownership of the hospital until the lead problem was fixed.

ANF state secretary Mark Olson said proposals like filtering the water to make it safe were not enough, and he has demanded the source of the lead be found and eliminated completely.

"We'd like to have an independent third party test the water to make sure that we don't want to have an Elizabeth Quay-type situation happening again at the Children's Hospital, it's way too important," Mr Olson said.

He said 98 per cent of ANF members declared they would not work in the new hospital until the lead was removed.

"They're not prepared to move over there to look after sick children. They know the risks associated with lead exposure, even minute amounts," Mr Olson said.

"We hoped that the Government would identify the source of the problem and told us all how they were going to fix it, that hasn't happened.

"Now it's getting to the stage where we don't want to see the Government announce some premature opening of this hospital until they have removed the problem of the lead."

Mr Olson said the Government was not providing clear answers or a clear resolution.

"Not just filter it out to a safe level but to actually fix it and get a third party, not the people who have constructed the hospital, not someone from the Government but a third party to confirm that the lead has in fact been removed."

Health Minister John Day said the Government's sole focus was the safe commissioning of the hospital and the safety of staff and patients.

"We will not open the hospital until we are absolutely certain that the water to be used by patients and staff meets Australian Drinking Water Guidelines," Mr Day said.

"The hospital can and will only be opened after approval of the water supply by the independent regulator, the WA Chief Health Officer."