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!
Sounds like “water hammer”. If you google that others can give a way better explanation of why it happens.
I fixed mine by closing the main at the street, and opening the faucet highest and furthest from the main. In my house that was an upstairs faucet at the opposite corner from the main. Released all the pressure and then turned back on the main. Noise left and hasn’t come back for 6~ months. There are knock arresters you can install or have installed that stop the problem before it happens.
So I’ve already done this one. Exactly according to the link posted a bit further down but no dice. I’m really confused as to why this only seems tied to the hot water though
Do you have a PRV? Is the sound worse at the PRV?
The hot water flow making the sound go away isn’t explained by a bad PRV but everything else could be.
PRV? Not sure what that is or where i would find it
Pressure reducing valve. Typically found directly after the water meter to reduce high municipal water pressure to reasonable residential water pressures.
I would also double check and make sure all the valves are fully open.
I think it could be a turbulence inside the pipes that resonates with the pipes and causes the knocking. You could try to fix the pipe to some wall.
I’m not an expert, but it sounds like your pipe is hitting a resonant/natural frequency. If this is the case, your best shot is to change that natural frequency.
Best thing I can think of to do that is to add a pipe support somewhere where the noise is occurring (likely where you have a long unsupported run of pipe). Look into a rubber-cushioned pipe clamp.
Might be caused by sediment in your hot water heater (assuming you are using a tank water heater). If you’re not familiar, there are tons of articles out there on how to clean it out.
A secondary concern is that you seem to have hot water moving through the system when you don’t expect it. Do you have any water circulators on the house on faucets (so you get instant hot water at faucets?). That could explain it. Otherwise, you might have a leak somewhere.
