01-23-2008, 04:42 AM
If it's a pressure reduction, (pressurized closed pipe on all ends) it may not be a leak as in water leaking. When I had some plumbing work done, a pressure gauge was put on the line for inspection. Well as you guess, it was registering a slow drop in pressure. Every pipe was visually checked and the worry was it may be an underground leak. Well, it turned out that one of the shut off valves to a fixture wasn't closed and that caused a slow pressure equalization from a faucet that opened ever so slightly. The plumber was embarrassed because it's such a common mistake that he should have rechecked all the actual wall shutoff valves not just that all faucets were turned off.