I removed an old water softener that sat for 15+ years and used PEX to reconnect the copper lines. Shortly after that I noticed a sound that has me feeling quite uneasy. You can hear what sounds like a repeating water hammer in this video

Why is this sound happening and how do I stop it?

** EDIT **

While working on this issue I've found that

  • the source of the knocking seems to be coming from a very close proximity to the pressure regulator
  • I can feel the floor shaking above where the pressure regulator is and about a 10' radius around that spot
  • I have an outdoor, frost-free spigot near the pressure regular which is also the first valve on the line and the water staggers in a rythm that matches the frequency of the vibrations.
  • 1
    Sounds like classic "water hammer" to me. Give the site a search for that and see if it gets you anywhere. That might also resolve your earlier question. Popham mentioned it there.
    – isherwood
    Feb 12 at 17:59
  • I was going to delete this question but I turned the water pressure down which fixed the repeated "water hammer" sound while the water is on but now the water pressure is so low that we can't have multiple faucets running at the same time. I'm starting to wonder if perhaps my pressure regulator is going out? That seems to be the source of the repeating hammer sound.
    – Jacksonkr
    Feb 12 at 22:26
  • @isherwood As far as I understand it, "water hammer" is a sound at the beginning / end of water being turned on / off whereas this is a consistently repeated sound about 3 times a second for the entire duration of while a faucet is on. Turning down the water pressure has helped but with multiple faucets on inside the home it's just as chaotic. This is the most insane sound I have ever heard coming from inside a home, there is nothing safe and/or natural about it.
    – Jacksonkr
    Feb 14 at 2:09
  • There a restriction somewhere. Either junk in the pipe or a valve not open enough. The junk is flopping around or the valve is getting played like a reed. Working DT once where the pressure is more like 60 instead of 40, I had a valve do that until I was brave enough to just quickly open it fully. - That ain't no WH.... that's the scene from Goonies!
    – Mazura
    Feb 14 at 2:39
  • 1
    Water hammer can absolutely be a continuous, repeating event. My grandparents house had a drinking water faucet in the sink that would rattle like a machine gun if you opened it just a little.
    – isherwood
    Feb 14 at 14:37

1 Answer 1


This issue has resolved itself. Here are my notes, in chronological order:

Leading up to the problem

  • I removed a water softener and replaced the missing section with pex
  • Before thinking to bleed the pipes above the site of work I tested the water on the faucet before the splice
  • I experienced the continuous water hammer and started researching that, in the mean time toilets were flushed and showers were taken - business as usual

Leading up to the "fix"

  • I bled all lines inside and outside of the home, problem stayed unchanged
  • I tampered with the water pressure and reduced the home to 40psi to reduce the sound to inaudible
  • I purchased a pressure gauge and hooked it onto the new section of pipe I'd previously put in
  • I cranked the water back up to 80psi
  • About this point in time is when I noticed the water hammer sound was starting to change
  • I re-bled the upstairs and got a small sputter from air at one point.
  • after fussing with the psi again I'm back up to 80psi in the home with no noise.

My best guess is that there was trapped air in the home but not in a way that caused an air lock. I suspect that through the violent shaking of the pipes from the problem and the changing of psi the air eventually worked it's way out but all I can really do is speculate.

Thank you to every who contributed to this resolution, especially "Tommy" a retired plumber who works part time at Lowes.

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