I've got a church that has 3 water meters for irrigation. theyve complained about high water bills, and their plumber said they shut off the backflow and the meter stopped spinning. i confirmed the problem a few days back, shut off the backflow and the meter stopped spinning. I forget the gpm on the meter, but it was rather fast. seemed alot faster than just a stuck diaphragm or something. there are no visible leaks that I can find, and they recently had a new parking lot poured when they added a new building. how in the word can i find the leak? just wait for the parking lot to collapse?