I have a thrumming sound in the plumbing. It is like a vibration---something like 50 cycles per second.. It sounds like it is in the ceiling of the downstairs bath. Almost all of the plumbing feeds through above that bathroom.
Unlike "pounding" this happens ONLY when NO water is running.
All I have to do to stop it is open a tap so a stream of water about 3/32 of an inch is running. It does not matter if it is hot or cold. A larger stream of water does not seem to make a difference.
If there is noise and I open a faucet it stops. If I close the faucet again, it stops again. If I let the water run for awhile and close the faucet, the noise may not start again for a few minutes or hours. It seems like the more water I run, the longer it will stay quiet.
When it is quiet, I can tell when the thrumming will start again because it makes a faint squeaking sound for a few seconds before the thrumming noise starts. Turning on water during the squeak will prevent the thrumming for awhile.
I tried turning off the main water valve--- to the entire house. Then I opened faucets and let water drain. This stopped the noises for a few hours, but then it was right back to ground zero. I have opened valves upstairs and downstairs and hose bibs. I have let the hot and cold water run full blast several times---one time for 30 minutes. I have tried opening different combinations of faucets when draining and when starting up again.
One time only: After doing the water off, drain the system routine I opened the main valve. I was in the downstairs bathroom. I opened the lavatory sink faucet (I'm pretty sure it was on all cold...but not positive.) and a full column of water came out as normal, except it looked like black ink. This lasted approximately 3 seconds. It has not happened again. The color was not dark brown, it was as black as black India ink.
I have been trying different things for two days now. I turn off the main valve whenever I can---especially when we go to bed---Who wants to get up in the middle of the night to turn on a water faucet?
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