I have a very odd issue that I can't solve, perhaps someone here could help. The pipe attached to my main shutoff valve is emitting a soft knocking sound at around 120 beats per minute. The sound persists as long as there is any amount of pressure, and I can feel it in the pipe nearby as well as in the valve handle itself. The weird part is that if I turn on any hot water tap, the noise vanishes. I'm a new homeowner so I don't have much experience, so any help would be appreciated. What I've checked so far:
Drained the system completely and refilled
Turned the water off overnight and checked toilets for leaks
I don't feel the pulse at the water meter line
Turning hot water on anywhere in the house stops the noise.
Thanks in advance!
Pressure reducing valve. Typically found directly after the water meter to reduce high municipal water pressure to reasonable residential water pressures.