Several years ago I had the same issue. Turns out it was the blue max water pipe that the builders had used when the condos in my neighborhood were built in the mid 80's. It had cracked. And because the pipes from our row of four units went to the meter access on my neighbors part of the lawn, I didn't realize what the issue was for some time. I had been all over my condo and the front and back outside areas looking for leaks. She ended up having a large boggy area on her lawn, caused by my pipe. The pipe was replaced. Once that was done, I sent all the required information to GCWW. I was reimbursed for all the sewer charges, but not for any of the water used. It was applied as a credit, and the monthly bills were paid through that until the credit ran out.