Inside the house, especially in two of four bathrooms, sounds like water is running to an outside tap. Not loud, but you can hear water moving through pipes. However, no taps are on, toilets are not running, no discernable leaks, outside taps not on. What could it be? When I shut water off to hot water heater, noise stops. But why would it continue to fill for hours?

To check to see if you have a hidden leak first shut down everything in the house, no flush, no drinks of water, and if you are on a meter go out and check the little pointer in the gage. It should not move or creep. If it does you have a leak. If you're on a pump then check the pressure gage after the pump builds up to pressure and shuts off. The gage should not fall and the pump come back on. If so then you have a leak. Hope this helps and thank you for rating my reply, Tom