I have a water leak (I think) but no water leak anywhere in my condo. I heard the hissing noise a week ago and still no water anywhere. My condo is upstairs and my garage (and neighbor garage) below. I've been here for about 20 years and water leaks started to happen about 10 years ago. It was really annoying ... I would get one every 6 months but being upstairs mean the leaks where on the garage ceiling and walls. Easy for me to fix...so I did several times (copper pipes and solder). Then the Home Owners Association (HOA) had a company add something to the water supply and the leaks stopped. It's been about 5 years since I've had a leak. Now I hear the hissing sound. I shut off the water to the water heater and still there. If I close the main shut off valve the sound stops after about a minute. This is why I figure I have a leak...probably underground.
I hear the noise loudest from the area of the water heater. I've ruled out the water heater pilot noise and the fluorescent lamp buzzing.
The picture with the vacuum is from 15 years ago when I change the water heater and I installed a bypass for the cold water line. The bypass goes from a little below the main supply in point to a little below the cold water valve for the washing machine. The blue line shows how it is. There was low pressure for the cold water line when using the washing machine ...it used to take forever to fill. The bypass fixed that. The cold supply keeps going up to the ceiling where it goes to several places in my condo.
The bypassed line (3/4 in) still goes underground. I didn't see a reason back then to cut and cap it. There are two pipes that go underground next to the water heater discharge pipe (there are two more to the left but I think those are the hot water). A 1/2 in and a 3/4 in. I'm thinking of cutting the 3/4 in pipe and cap it first and see if the hissing sound goes away. But this only makes sense if the hissing sound of water is the source point of the leak?
The leak could be the 1/2 in pipe. I'll have to bypass/cut/cap it ... a bit more work. Then I'll be out of ideas. So before I start tearing dry wall out ... any chance the hissing sound is not where the leak is?