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Thread: Loud vibration coming from pipe, Pretty sure it's NOT water hammer

  1. #1
    DIY Junior Member aboynamedmoose's Avatar
    Join Date
    Jun 2013
    Marietta, GA

    Default Loud vibration coming from pipe, Pretty sure it's NOT water hammer

    Hello all,

    This is the first time I've posted on this site. I know there are many threads about water hammer but I'm pretty sure that's not my situation, I could easily be wrong though. I live in a two story ranch house with the basement unfinished and the top floor finished. About a week ago my wife heard a loud noise in our basement that sounded like it came from our copper plumbing pipes, she said it only lasted a few seconds and then stopped, she said it happened several minutes later and stopped again. I was asleep so I didn't notice it. The next night before I went to bed I heard the noise so I ran downstairs to the main line that comes in the house from the street and sure enough it was vibrating so fast and loudly it was almost as loud as an air compressor. I put my hand on the pipe and could feel it vibrating. It only lasted a few seconds and then went away. I have lived in this house for 35 years and have never heard the pipes make a noise like this. The next day I went and bought a water pressure gauge and put it on the spigot outside closest to the PRV, it read 140 PSI. I knew that was too high considering the current PRV was set at 50 PSI from the factory. So I went out and bought a new Watts brand PRV - same model as the old one but lead free now, and replaced it along with my main line shut off valve. I had the old style shut off valve that you have to turn a hundred times to turn off or on so I replaced it with a quarter turn ball valve. After I was finished I turned the main valve back on and let water run out of the tub, faucets, etc so all the air was out and then I checked the pressure again and it was at 50 PSI so I figured that would fix the problem. Unfortunately it didn't, I've heard the same noise every day at least once since then and I heard it earlier tonight and it lasted longer and was louder than I've ever heard it.

    A little about the house:

    All the supply pipes in my house are copper.

    The main line comes in from the meter up close to the road and underground and under my driveway into my cinder block wall and up the inside of the wall to the plumbing pipes that are attached to the bottom of the floor joists.

    About a month ago or so I got a letter from our county water system stating they would be replacing the meters in a few months and they would be installing a back flow preventer on the meter. The letter went on to say that I would need to install an expansion tank to my hot water heater if I didn't have one (which I don't right now). I thought the county messing with the water line might have been the problem but they haven't even touched my meter yet and I haven't seen the working in the neighborhood either.

    The noise DOESN'T happen while a faucet is on or the water is running or someone has just flushed the toilet, it will happen out of the blue when no water is running in the house.

    If anyone has any suggestions or solutions I'd be extremely grateful because the noise/vibration will drive me nuts out of worrying and I don't want to mess up my appliances or pipes.

    Thank you,


  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    A PRV creates a closed system. The check valve the water company will create a closed system - reinforcing the one you already have. ALL closed systems need an expansion tank. So, add one! As you use hot water, it gets replaced with denser cold water. When you stop using, the WH heats that cold, dense water, creating hot, lighter, expanded water. Your pipes don't generally expand to accommodate it...something has to give. It's probably the weakest valve in the house, but it could easily be a supply hose or the check valve in the PRV (it might have a high-pressure bypass) or more commonly, the T&P valve on the WH. Regardless, if the water pressure gauge you bought has a tattle tale hand, leave it on for say 24-hours...my guess is that the water pressure will spike at least once above the 50psi setting because of water expansion...stop that, your noise will probably go away. Where I live, all houses are required to have an expansion tank, regardless of whether it is a closed system or not to allow for the addition of a check valve...check valves prevent potentially polluted water from your house from getting back into the supply system and are a safety device many places are adding, or already have.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Junior Member jjtrindc's Avatar
    Join Date
    Jun 2006
    District of Columbia


    Your problem sounds a lot like mine. Not that I can help you, but we can monitor each others responses...


  4. #4
    DIY Junior Member ksopworker's Avatar
    Join Date
    Nov 2013


    Did it ever got solved? I am having the same problem

  5. #5
    DIY Senior Member kcodyjr's Avatar
    Join Date
    Nov 2013
    Chelmsford, MA


    Just a wild guess, since he didn't come back looking for something else to try, either the expansion tank worked, or he hired a pro and didn't take the trouble to tell us about it.

    Either way, the point stands, if you don't have an expansion tank in your hot water system, you need one ASAP.

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