Lead still in water at new Perth hospital

The source of lead contamination in drinking water at the new Perth Children's Hospital still hasn't been found and work continues to flush it out of the system.

Reports of the contamination emerged almost three months ago and were a further embarrassment to building company John Holland, which installed roof panels containing asbestos sheeting at the $1.2 billion facility.

Premier Colin Barnett said the lead levels were well below most international standards but still did not meet Australian standards.

"It is frustrating. The state government and the health department already have 300 staff working within that hospital," he told reporters on Thursday.

"But until this passes all the tests, the children won't be moved across."

The hospital is already a year overdue and deputy premier Liza Harvey said earlier this week the state government's patience with John Holland was wearing thin after it again missed the handover deadline.

It's unclear whether the hospital will open before the March state election as there is no revised completion date.