We recently purchased a place with damage from frozen pipes. About 30% of the pipes have been replaced, along with the water heater, the toilets, all sink faucets, all shower valves, the water meter, the pressure regulator, the main water valve, all under-sink valves and supply lines, toilet valves and supply lines. Essentially, almost everything that comes into contact with water has been replaced (with reason - they were leaking).
Because I'm paranoid about this, I turn the main water valve off when leaving the house. This is when I first noticed the problem. After the main valve has been turned off for a few hours, turning it back on produces a small rush of water into the system (as recorded by the water meter). According to tests (shown below), this seems to be leaking about 1/2+ gallon per 24 hours. This has been going on for over two months, so 30+ gallons has leaked out so far. The problem is, I have visual access to all of the water pipes. I've found leaks of less than an ounce of water, but this 30 gallons seems to have disappeared. It's not inside - nothing is wet. It's not outside - there are only two hose bibs, no sprinklers, and no sign of water anywhere. In addition to just turning off the main valve, I've also tested this by turning off ALL the valves in the house in case there was a slow leak through something like the toilet. Same results.
I've done the following tests:
Water pressure test: Hooked up water pressure gauge to cold water laundry supply hose bib (there is no washing machine currently hooked up). Starts at 50psi. Turn off main valve. Without using water, it loses approximately 4 psi per hour until it gets down to about 15 psi. It's not a constant 4psi per hour, but rather starts at 4psi and then slows as the pressure is reduced. At 15psi, it seems to stop, but I'm not sure yet if it would go to 0psi if given the opportunity.
Water volume test: Clear pipes of all air (run the water everywhere until it stops spurting air). Turn off main valve. Drain the water from the lowest faucet (includes opening upper faucets to get more water to drain. Drained water measures 205 ounces. This is repeatable. Turn main valve on. Clear air from pipes again. Turn main valve off. Without using water, wait 12+ hours. Drain water again as before. Drained water measures 165 ounces. This is repeatable. This is about .3 gallon of water. When the main valve is turned back on, the water meter registers about .1 gallon. I suppose this could somehow be a result of a loss of pressure without a loss of water?
Water meter test: Clear pipes of all air. Turn main valve off. Wait 12 hours without using any water. Turn main valve on. Meter records 1/10th of a gallon of water rushing into the system. The meter is rated to record 1/16th gpm and higher so it could never detect a small leak. Note that, in conjunction with the water volume test above, the meter records inaccurate (low) numbers in relation to the measured drained water.
Pressure spikes: I can't see that this has anything to do with the phantom leak, but it might be relevant. In daily use, the water pressure will spike from 50psi to 80psi and sometimes higher (up to 110psi so far) after any use of hot water. According to the city, their meters don't include a dual-check valve and excess pressure should be able to backflow into the main line. I'm planning on installing a dual-check valve and thermal expansion tank anyway because of the pressure spikes, but haven't gotten around to it yet. I don't know what the city's water pressure is.
This probably won't help, but here - http://www.use.com/e0cd78ebeb032f51faa7
- is a picture of the main line (a) coming into the house, (b) past the main valve, (c) past the water meter, (d) past another valve, (e) past the pressure regulator. The water meter has been replaced since this picture was taken as it had a slow leak.
My question: Is there any way this could be something other than a water leak? Even though there is zero evidence of water, if it still sounds like a leak, is there any way I could test for it? Air pressure test and a stethoscope? Any suggestions at all on how to find out what's going on here? I'm having dreams of water pooling up somewhere and when it reaches 1,000 or so gallons, it all comes pouring out.
Thanks so much for any suggestions!