I had a PRV that was leaking. Replaced it and things seemed fine for a few days. After that I started getting humming, vibrations in the pipes whenever a a faucet or water source was opened. It went away or seemed to if two or more faucets were opened at same time. No noise when water was off. No hammering. Drained the pipes of air. Was fine for a few days then sounds came back. Turned the pressure up to sixty PSI. Was fine for a few days and the noises came back but not as loud. I put in another new PRV and the story repeated itself. Any suggestions on what to do next?