Tapping noise in pipes when water is running

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by ThomasE, Aug 4, 2009.

  1. ThomasE

    ThomasE New Member

    Jul 16, 2009
    Ever since I replumbed my house from rusty galv. to PEX my pipes are generally much quieter. However there is a mysterious, very faint, tapping noise.

    Sounds like a faint rhythmic tapping.The cadence of the tapping changes with water flow, from, say, a couple of taps per second to 5 taps per second. Seems like, the higher the water flow the higher the cadence. The cadence is constant over time for a particular flow rate (does not sound like thermal expansion).

    Happens only when water is running. The noise is present regardless of which faucet throughout the house is on (although the cadence changes with the flow rate). Does not matter whether hot or cold water is on.

    When the flow is low it often sounds like a two pitched tapping, a bit like the tik-tak of an old mechanical grandfather clock.

    The noise is faint and is really audible only under my main bath. This is also where my 1" copper service line enters the house and connects to the 1" PEX line which then goes to the main PEX manifold in the garage. All pipes are in crawlspace.

    The noise is faint so it does not really bother me. I’m just wondering if it may be a sign of a problem.

    P.S. Water Pressure 63 PSI. My water heater is set low (probably 110-120F water temp)
  2. Winslow

    Winslow Plumber

    Dec 30, 2005
    could be either the PRV or the meter.
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  4. ThomasE

    ThomasE New Member

    Jul 16, 2009
    Forgot to mention there is no PRV...

    Also when I turn on two zones at the same time in my sprinkler system (that would make about a 12 GPM flow) then sounds like there's a small helicopter underneath my bathroom. Not loud enough to wake anyone up but a little annoying if you're trying to have a quiet time. But as long as it is not a harbinger of future problems I can live with the noise, no problem.

    P.S. The 1" PEX taking water to the sprinklers branches off the service line just a couple of feet after the service line enters the crawlspace.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    My vote is the water meter...it is the only thing common. Well, if you have an old gate valve for a shutoff, I suppose the gate could be rattling in the flow...that's just a wild guess, never seen it (but I'm not a pro, either). Make sure the main shutoff is fully open.
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