I've searched thru your forums (and they're super helpful!!) but still haven't found the solution to my problem. I'll try to be as specific as possible, and hope your knowledge base of readers can solve my problem.

As posted by numerous others... I too have an occasional noisy water pipe problem. Sounds like a low moaning, groaning, vibrating noise that rattles all the pipes in the house. Hard to detect the actual source of the problem since it rattles all the pipes.

The noise occurs directly AFTER ANY WATER IS USED, Hot or Cold.
The noise occurs after water is used from any source: toilet, faucet, shower, humidifyer.
While the noise is occuring, if I start water flow again, the noise stops.

What's really strange, is that the noise will bother me for a few days... and then without any apparent change in the dynamics of the house, it will just DISAPPEAR?!?

I've checked, and I don't seem to have a PRV in my system.
I do have a whole house water filter, and a softener system.
I've put BOTH the filter and softener on BYPASS, and the noise still occurs.

I have water hammer arrestors on the hot and cold water lines on a recently remodeled shower that's on the first floor of the house. They're pretty large, about 8-10" long.

I DO have an IN HOUSE WATER METER. Could this also be a PRV, and potentially the source of the problem?

Thanks in advance to everyone for you help.