WA Premier Mark McGowan says he was not aware of corrosion problems at the Perth Children's Hospital, despite his government releasing two separate reports which detailed the issue earlier this year.

It has been revealed some sections of the stainless steel drinking water pipes at the hospital have had to be replaced three times after they corroded at an extraordinary rate.

The problem was mentioned in two reports released by the State Government in April — one from the Building Commission and one assessing the potable water system, known as the Jacobs Report.

The corroded pipes were last replaced in March by a new company, but they are not scheduled to be checked inside for signs of corrosion until next year.

Mr McGowan was asked on Wednesday whether that internal testing should be brought forward, to ensure there was no risk of leaks when the hospital opens.

"The story yesterday was news to me, I hadn't heard of that issue before," he said.

"Clearly we will make sure that before people are in the hospital, that the water is safe.

"There will be an ongoing program of monitoring and before people, patients, staff are in the hospital, it will be safe."

The opening date for the $1.2 billion facility, which was supposed to accept its first patients 18 months ago, has been repeatedly pushed back and it is still not clear when it will open.

The Government is still grappling with a separate water quality problem with lead contamination.