The construction of Perth's new children's hospital is complete but the facility won't open until July at the earliest as the government is still dealing with elevated levels of lead in its drinking water.
The government has taken control of the long-delayed project from builder John Holland now that "practical completion" has been achieved, it was announced on Thursday.
However, it is costing the taxpayer $6 million a month while it remains unused, Treasurer Ben Wyatt said.
He said two sections of the $1.2 billion hospital still have elevated levels of lead in the drinking water, caused by lead dissolving from brass fittings.
Phosphate will be flushed through the pipes and although it's believed it will resolve the issue within a week or two, the process will continue for 18 months at a total cost of $120,000.
"John Holland have never accepted and won't accept that it's the brass fittings on their site that is the cause of lead, and that has been a point of contention," Mr Wyatt said.
The Department of Health is now able to access the site without restriction, so final testings can take place before the chief health officer declares the hospital is fit to open.
Health Minister Roger Cook said the commissioning process would take at least 10 to 14 weeks and admitted it was a frustrating situation.
"We will make absolutely sure that the hospital is safe for kids when it opens."
John Holland WA regional manager Lindsay Albonico said the hospital was set to be one of the world's leading paediatric hospitals.
"John Holland made a commitment to the children and families of Western Australia to deliver a world's best hospital, and we are immensely proud of what we have achieved," he said.
The hospital was originally flagged for completion in 2015, but asbestos was found in roof panels last year.