For the last month or so I have had an issue with a loud pulsating sound coming from the water pipes. I’m not sure that it is water hammer, it happens when I flush the toilets mainly. I’ve tried adjusting the PRV up and down with no success. What does seem to stop it is if I partially close the manual shut off located just before the PRV. This seems to make it stop. If I let the water free flow it does it again. Any thoughts? I attempted to change the PRV but it seems seized and wouldn’t loosen at all, so if that is the culprit, I guess a plumber will have to be called.
It may not be the PRV itself, but rather the length of the spur going to the PRV might be just right for resonance with frequencies generated by flow.
What kind of shut-off valve is before the PRV? Is it a ball valve or another type?
EDIT I have a utility sink in the garage on which I had a plumber do the rough-in and I installed the sink, faucet, and connected the ubiquitous braided ss flexible supply lines. At low to medium flow the hot squeals loudly. The cold is fine. I have a minimal tankless water heater. I have not been able to study this and figure out anything.