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Rythmically banging pipes.

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  • Rythmically banging pipes.

    I had a service call this morning and the homeowner offered me a surprise problem while there.

    She was able to cause the water piping to bang rhythmically throughout the house. The pipes would bang at an approximate rate of 3 Hz. (times per second). I happened to be in the basement when this happened and immediately grabbed the 1/2" cold water pipe which was bouncing up and down about 2". My grabbing the pipe had no effect on the rhythm.

    It turns out for the pipe to bang in a manner that would make a conductor leading the "1812 Overature" proud a very specific set of conditions was required. The toilet tank had to be filling. The shower in the bath bay adjacent to the toilet had to be running. If the tub filler was operating the banging would not occur.

    I removed the shower head and let the water flow out of the shower arm unencumbered. No banging. I replaced the shower head with a new shower head. The old shower head was a massaging shower head, and I replaced it with a massaging shower head I robbed of a Delta 1700 series tub shower valve I stock in the truck.

    Problem solved. Apparently the old showerhead vibrated at a frequency that excited a ~3 Hz resonance in the pipe/water system which in this case created a feedback loop which further excited the pipe system.

    I ran into a similar issue about five years ago when a ceramic disc cracked in a kitchen faucet. That system differed in that the vibration would continue when the water was off!! Someone in a different apartment would have to go turn their kitchen faucet on and off to get it to stop. (What a pain. You neighbor gets a drink of water at 3 am and you have to get up to stop the banging in your apartment. ) The solution in that case was replacing the faucet since it was some offbrand I couldn't get parts for.

    Here are a couple pics of the showerhead that created the problem was free to the homeowner and was supposed to save water. (While risking their sanity).
    Attached Files
    Time flies like an arrow.

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  • #2
    Re: Rythmically banging pipes.

    Have not run into the shower head as the problem yet. Have had;pressure balancing spools,ballcocks,hose biibs,loose facuet washers,partially closed e stops, vacumnn breakers,solenoid valves cause vibraton like that.

    I will pass this on to the other guys in our shop thanks for the info.