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Tapping noise in pipes…

Posted by orourke (My Page) on
Sun, Aug 2, 09 at 1:55

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)

Follow-Up Postings:

RE: Tapping noise in pipes…

Hi. I'm not sure if this is a valid answer, but I have the same issue SINCE about 1 year ago when I turned the MAIN water valve off to the house.

I had to do a bit of repair work to the shut-off valve going to the commode, and my main valve to the house hadn't been turned off in about 10 years since I bought the house. (It actually wouldn't shut the water off all the way, and I've since had to have it replaced.)

When I turned it back on, 'junk/small pieces' came out of several of the faucets, and in the bathroom (which is right behind the laundry room and main valve/water meter), I noticed this tapping you're talking about. At first I was nervous as I thought it was dripping behind the wall. I usually only notice it when the washer is filling up though, but like you said, its speed depends on the water speed. It is constant, but if I turn the sink on while the washer is filling, the tapping speed increases, and then decreases when I shut the sink off.

I did notice that if I put my hand on the main valve (which is just inches before the water meter) when I hear the tapping, I can feel the tapping in the valve, and in all honesty, it sounds like it's coming from the water meter to me.

A plumber recently listened and said it is not unusual for the meter to make that sound, and it basically reverberates throughout the pipes.

Whether that's true or not, I don't know, but since I turned the main valve off for the first time in a decade and turned it back on, I get the same sound you're referring to.

Perhaps someone here can verify that and let us know if it's true or not, or if it's indicative of a problem.


RE: Tapping noise in pipes…

I had not thought about the meter as a possible noise source. I have to say, it does sound like a gear going around with a few missing teeth or a gear bouncing around a worn out bearing.

This morning, I went out to my service line where the line enters the house and I can the tapping there if I put my ear on the pipe. Then I went to the sidewalk and opened the meter and I can still hear the noise at the meter but it is faint. It is actually louder in my bathroom than it is at the meter. But perhaps the noise travels through the water and shows up under my bath which is where my main copper service line is clamped to the joist?

RE: Tapping noise in pipes…

Our office/bedroom is right above the water meter, when the sprinkler for the garden is running you can hear the meter. TV, radio and washing machine noise blankets the sound the rest of the time.

RE: Tapping noise in pipes…

Following your suggestions I did some more targeted "googling" and the most plausible cause seemed to be noise from the water meter (BTW, I have actually heard similar noises at the gas station pump when filling up gas…). What still puzzles me though is, how come the noise seems louder in my house than at the meter when the meter is 40’ away from the house by the sidewalk?

Also would changing the service line from rusty galv ¾" to 1" copper (as I did recently) enhance transmission of any water meter noise to the house? At another site, I read somebody mentioning that the increased water flow could have dislodged some sediment from city pipes which can then get stuck in the meter and make noise…

RE: Tapping noise in pipes…

That's when mine started... when I had to turn the water off to the house, then when I turned it back on, small 'sediment' or something corroded/broken came out of one or two faucets, and my tapping started.

My meter is inside the house. I can 'feel' the tapping in the meter when I put my hand on/by it, although I can't really hear it much there, but when I go in the bathroom, I can hear the tapping quite clearly in the pipes.

I don't know whether the sound is magnified because of the water/pipes, but I really think the meter is the source in my circumstance.

Hasn't seemed to cause any problem, just annoying since it didn't used to do that before the sediment/stuff made it through the lines.

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