A report leaked by a whistleblower revealed on Thursday that the health board was told areas of the flagship £800 million Queen Elizabeth University Hospital campus were at a "high risk" of infection before opening in 2015.
Another two reports, also leaked to Labour MSP Anas Sarwar, suggest issues were still pervasive at the hospital in 2017 and 2018.
The death of 10-year-old Milly Main in August 2017 after she had beaten cancer has been linked to an infection caused by contaminated water.
Her mother, Kimberly Darroch, 35, from Lanark, has said she is "100 per cent" certain that contaminated water caused the infection, Stenotrophomonas, listed as a possible cause on her daughter's death certificate.
Speaking to BBC Scotland, Ms Darroch said she was "shocked" by the latest leaked report.
• READ MORE: Mother of Milly Main who died after contracting an infection at Glasgow children's hospital feels 'let down and lied to'She said: "The fact that they've known since since 2015 ... it's absolutely disgusting that nothing was done about it and no action was taken and the hospital was still opened.
"I believe Milly would still be here if action had been taken. I've no doubt in my mind that Milly would be sitting beside me, right now.
"There is no words to describe that pain of knowing that if things had been different, that if things had been sorted with the water, she would still be here.
"I think the health board needs to be held to accountable for the mistakes that they made."
A spokeswoman for NHS Greater Glasgow and Clyde said: "We are very sorry for the ongoing distress that has been caused to Ms Darroch and we want to provide parents with as much support as possible.
• READ MORE: Mother of 3-year-old boy who died at a scandal-hit children's hospital says her family is being ignored"We are in contact with Ms Darroch and would like to meet her to answer her questions if she would be happy to do that."
The health board maintains it was not possible to conclude that infections identified in 2017 were connected to the water supply because it was not required to test for bloodstream infection Stenotrophomonas at that time.
The first of the leaked independent reports carried out by contractor DMA Canyon in 2015 found five of the eight plant rooms that supplied water to the rest of the hospital were deemed to be "high risk" and identified dirty water tanks.
A report on a follow-up inspection in 2017 found "no significant water system alterations" with the tank issue unresolved.
The health board said all issues raised in the inspection reports were acted upon, routine water sampling was carried out since the hospital opening and there is a "safe and effective" water supply.
A public inquiry into issues at the hospital has been called by Health Secretary Jeane Freeman.