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I am on city water. I recently replaced my galvanized pipe water line with PEX in my home (every fixture), and I now have violent pulsation in my water lines when I turn on a fixture. The PEX is well strapped, and I have tried two, brand new pressure reducing valves to no avail.

The pulsation happens when I turn on fixtures, not when I turn them off. I have shut the toilet valve, so I know it is not that.

When I turn off the valve to the irrigation hose bib and sprinkler box, the pulsation is less violent, but still exists.

The home is a single level home, so everything runs along the crawl space and up into the fixture. I have one bathroom, one kitchen, and one laundry room.

I'm using a tankless water heater, but the pulsation was there a week ago when I had a tanked water heater. Pulsing happens with hot or cold water.

When I put a pressure gauge on my hose bib, the black needle shows 40. The red needle goes past 200 psi.

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Tee goes right to hose bib (galvanized pipe) and sprinkler box (PVC). To the left leads to the house fixtures

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Check out the video of the violent pulsing by watching this video

And check out my water line, from where the city comes in to where it leads to the fixtures by watching this video

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  • Is it just when it opens or it keeps going while water is running? What if you test pressure inside?
    – rogerdpack
    Nov 1, 2023 at 6:19
  • Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.
    – Community Bot
    Nov 1, 2023 at 10:21

1 Answer 1

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Every time water flow changes direction, the change in momentum causes a steady force. Increase the flow rate and the force magnitude increases. That heavy concentration of fittings around your PVC shaped into a U (including the incoming water's elbow and tee) really grabs my eye. The movement of a fitting somewhere is disrupting pressure to cause a change in force at another fitting, where the two (or three or four or...) are resonating. Rather than tracking down the exact resonating parts, the solution is to stiffen up all points where there are turns in the pipe. Basically all of the 90s and tees.

@FreeMan suggests bending pex around corners instead of fittings. Good advice. It's cheaper and more reliable. Just remember that these turns will also have a force associated with changing momentum, so they still need to be secured.

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  • One of the best parts about PEX is that it bends quite nicely, eliminating the need for any elbows at all, except in the tightest of spaces. The short sections coming from (?) the PRV(?) - that could have easily been 1 piece of PEX bent in a nice, smooth arc - could even have had a $2 "curve holder" (or whatever they're called) snapped on to ensure the bend radius wasn't too tight and to screw the pipe to the rafter. The PVC "U" could have been redone into a simple "T" by the looks of it...
    – FreeMan
    Nov 1, 2023 at 12:37
  • @FreeMan, I've seen Us like that, where I always assumed that they were detailed to relieve stress from thermal elongation. Now that I think about it, that detail looks out of place with soft material like PEX instead of something like steel.
    – popham
    Nov 1, 2023 at 18:15

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