I have a shower with a Moen Posi-Temp valve.
Sometimes when in use it will start to vibrate at
maybe around 8 Hz.
It sounds like thump-thump-thump,and pretty strong.
It sounds worse if I am standing in the kitchen,
which is under the hot water heaters; sounds
like somebody is up there hammering on them.
Is this just an obnoxious noise,
or is it a hazard of some kind?
How can it be fixed?