We recently moved back into our beach house after hurricane Sandy. During the storm repair the lower level was rebuilt including moving a bathroom and moving the house valve (only a few feet). We always now hear the sound of water running through pipes (a whooshing sound)even though no water is running. Here is the strange part. When I shut the house walve ( this is inside the house where the water line enters the house which is in the wall behind a panel)the pitch of the sound changes slightly but it does not go away. One would think if there was a leak after the valve the sound would stop. In addition when we run water in the house we hear the usual sound of water running in the pipes layered on top of the first sound. The pitch of the first sound does not change. The plumber is stumped as am I. When could possible cause this? It's pretty annoying.
2Do you have central air conditioning, and is it running when you hear the sound? Maybe a whole house fan? Some other device that is running, and is in close proximity to a water pipe, or passes through the same framing member as a water pipe?– Tester101Jul 12, 2014 at 12:22
Do you have a water meter that would indicate when water was running through the meter? Can you check the flow of any waste water down the drain?– DJohnMJul 12, 2014 at 19:05
Could the water pressure regulator be faulty? It may be "transmitting" pressure changes from the street main into your system. If you neighbor flushes a toilet....you hear a gurgle!– Steve WellensJul 29, 2020 at 4:23
Did you ever get this resolved? If so, please give a check-mark to the answer that helped you the most, or write up your own answer explaining what you did to get it fixed and give yourself a check mark. That will help others with this kind of problem know that this has a resolution and is a good place to look for their answer– FreeManJul 29, 2020 at 17:57
I suspect the sound is from the drain pipes, and comes from a leaky toilet, beacause that's the most common thing that has a stored reservoir of water to keep leaking after you shut off the main valve.
You might try leaving the main water valve shut off for several hours. If the sound eventually stops, go around and look in your toilets to see if any are now empty in the top tank (without you flushing) - or speed the process up and flush all the toilets after shutting off the main water valve and see if the sound then goes away shortly after that.
If you'd like to check on @Tester101's theory, try shutting off the main electric breaker and see if the sound stops or not.