Mysterious sound coming from basement, related to water pipes

Question

At times I hear these banging sounds (not very loud) when in my living room. I go to the basement (below the room) and it sounds like it's in the ceiling (finished basement). I put my ear to the wall and try different locations to hone in on the location.

At first I thought there was a mouse in there, but it's not consistent with animal sounds. I checked the hot water heater (next room over) but don't hear anything. Now, recently I discovered that when I turn off the main water valve, the sound goes away.

Keep in mind that no water is running in the house at this time. Also, there are no leaks to be found anywhere. When I do put my ear on the hot water heater I hear noises but I'm not convinced it's occurring there.

My latest theory is the sound is being amplified somehow between the floors, perhaps the pipe is moving slightly. But as for what may be causing the pipe to make noise I have no idea.

I do have very high water pressure in my area. The house has a pressure reducer but I've busted a few garden hoses which are not on the reducer.

I tried recording the sound but it's so subtle that my phone playback does not indicate it. It is noticeable enough upstairs that my wife and I stare at each other in horror when it happens

Any ideas? Thanks

Answer 1

It's probably just the pipes expanding and contracting under temperature changes. They can bind on an anchorage, then suddenly break loose. The floor and pipes do reverberate, amplifying the sound. The tension release and sudden movement can be very small, yet the resulting sound rather startling.

If you can identify where the pipe is hanging up, you can replace the anchor with one that has a plastic liner that is resistant to binding. Or simply loosen the anchor or remove it, wrap the pipe with cloth tape, then reinstall the anchor.

It can be difficult to locate all the pops and creaks, they seem to come from nowhere sometimes. You should at least be able to quiet the worst offenders.