plumbing question...rhythmic tapping coming from pipes.

[KinzeMech]

I couldn't figure out what was the most appropriate forum for this question, but I know someone here will know...

My house has 1/2" copper water line. I have an unfinished basement, all the plumbing is accessible directly overhead, in the basement, no drop ceiling or any other overhead obscurement.

When there is water usage (mostly shower/bathtub/toilet fills are most audible) there is a rhythmic tapping coming from the plumbing. It's just a tap tap tap tap sound. The frequency remains fairly constant, but changes in flow can slightly increase or decrease the volume. I've been here almost 4 years, and it's always been that way. Idle curiosity finally drove me to ask about it.

What could be causing this, and is there any possibility it indicates an actual problem I should do something about?

 

[Buckgnarly]

Is it hot water pipes expanding? Mine do that when the washer is first turned on and filling.

 

[WhoWhatNow]

It's water hammer. Air in the pipes.

 

[Rookie2]

could be expansion/contraction of the copper pipes creaking at the clamps that attach to the floor joist. maybe a sticking water pressure regulator.

 

[SweetD]

Good question - I have a similar thing going on with the upstairs shower - kids' bathroom. When they shut the water off in the shower, the pipes rattle for a couple seconds. Always assumed it was a loose fastener to the stud or whatever...or ghosts!



Dave

 

[KinzeMech]

I don't think it's a temperature change, as it occurs with a running shower, or also with a toilet fill (cold flow only).

I thought water hammer due to air in the pipes was more of a thud/bang sound that occurred when a valve was rapidly closed. This is a very mellow tap at a frequency of about 2 Hz, with water flow at a relatively consistent flow rate.

 

[RivennHewn]

Install a few of these near the shower, washer, dishwasher, ect.

http://www.homedepot.com/p/SharkBit...4&srccode=cii_35912516&cpncode=26-393808580-2

 

[KinzeMech]

Install a few of these near the shower, washer, dishwasher, ect.

http://www.homedepot.com/p/SharkBit...4&srccode=cii_35912516&cpncode=26-393808580-2

I've got that built into the original pluming at the kitchen sink and each bathroom sink. The 1/2" copper lines coming in under each of those sinks have a tee fitting with about a 6" vertical length of pipe, capped at the end. I do not know if the toilet/shower/bathtub plumbing contains the same, as it would be enclosed in the wall if it is present.

 

[Beemer533]

Good question - I have a similar thing going on with the upstairs shower - kids' bathroom. When they shut the water off in the shower, the pipes rattle for a couple seconds. Always assumed it was a loose fastener to the stud or whatever...or ghosts!



Dave

This is water hammer...

For the OP's issue, I would have guessed a pipe is rubbing somewhere, but not sure if it would be "rhythmic"..

Maybe a valve in the basement isn't fully open?

 

[RivennHewn]

I have an exterior hose bib that I like to leave on, and use the hose end to shut off the water.
Problem is, when I do that I get a hammering noise when I run water in the house.

Thinking mine may be a faulty anti siphon vacuum breaker.

Backflow preventer on an irrigation system may be a possibility too.

Do you have anything odd hooked up to your system?

 

[NUTTSGT]

Is the copper pipe properly hung or does it need a few more hangers ? My first guess is the pipe is humming from the movement of water.

 

[KinzeMech]

Is the copper pipe properly hung or does it need a few more hangers ? My first guess is the pipe is humming from the movement of water.

I don't know what constitutes properly hung, but this idea has merit.

Where the pipe runs perpendicular to the joists, it is supported every third joist. Where it runs parallel to the joists, it is supported about every 6 to 7 feet, in a rather odd way. There are short lengths of copper pipe with the ends flattened as though by a hammer, with the flattened ends driven into the joists. The fluid pipe rests on top of the short support pipe, and at these points the pipes appear to be soldered together, externally. I've always thought that looked like the oddest way to support a pipe, but I guess 30 some years ago when the house was built, copper wasn't as expensive as it is today.

The noise is more difficult to discern in the portion of the pluming that runs across the joists. Maybe the better support there is either preventing or dampening the sound.

 

[NUTTSGT]

Can you post a picture of these homemade hangers ?

 

[The Cobbler]

.... it is supported about every 6 to 7 feet, in a rather odd way. There are short lengths of copper pipe with the ends flattened as though by a hammer, with the flattened ends driven into the joists. The fluid pipe rests on top of the short support pipe, and at these points the pipes appear to be soldered together, externally. ....

...

The plumber did that instead of using wood 2x blocking to support the pipes

 

[KinzeMech]

Can you post a picture of these homemade hangers ?

I had that idea too. I've only ever seen that on this house, and have been wondering if it was a common practice or not. I can do that after the weekend. My wife is out of town for the weekend, and she knows where the camera is.

 

[A_Pmech]

Copper expands at .000009" / inch / degree F.

If the pipe is 20 feet long and the water temperature changes 5 degrees, the pipe becomes 11 thousandths of an inch longer or shorter.

Small changes in temperature will make the pipe move enough to make a creaking noise.

 

[KinzeMech]

This is true, but copper is rather conductive. I think that 10 minutes into the shower, the pipes have reached thermal equilibrium with the water, yet the tapping continues.

There may be temperature changes involved in the first minute or two, but there is no change in the sound. It is the same approximate volume and frequency, from the beginning of the shower, to the end. When my wife gets home with the camera (gone for the weekend) I may try to catch a short video that includes the sound. I don't feel I'm describing it adequately.

 

[RivennHewn]

I'm thinking it's more a pressure issue than temp. or attachment.

Do you have a expansion relief tank on the WH and a PRV on the main coming into the house?

 

[BruceH]

I just went thru this. The pressure regulator failed after 14 years. Replaced it and problem was gone as the old one could not hold the pressure steady and was fluttering and causing spikes. Apparently this is common.

 

[The Cobbler]

water meter ?

 

[steel 35]

Do you have a expansion relief tank on the WH and a PRV on the main coming into the house?

I added one a few weeks ago, put it on a drop tube that had a plug for kicks!
It really helped with the hammer from a toilet flush or Dishwasher, and the constant rattle of either hose spigot, and the variable squeal of the shower.
I know my pipes are loose attempted to tighten once and it helped briefly.
Best of luck.

 

[tipsy]

Does original poster have a water softener? These have a flow meter in them to gauge when to regenerate automatically. Sometimes that flow meter will tick tick tick as it's got water flowing through it usually because it's going bad or sometimes just because it has some mineral deposits caught up in it.

 

[LS6 Tommy]

I just went thru this. The pressure regulator failed after 14 years. Replaced it and problem was gone as the old one could not hold the pressure steady and was fluttering and causing spikes. Apparently this is common.

^^^THIS^^^

Tommy

 

[tcianci]

Only one guy so far guessed correctly, it's the water meter itself. Check it out next time you're running the water, and notice how the volume of the noise increases with the volume of water you're using. Hot, cold, makes no difference. Mine sounds like a machine gun when the irrigation is running!

 

[ColoMid]

First Post Here.........
I had a similar problem in my former home of 40 yrs.
An odd knocking sound would appear after shower use.
After months of looking, listening in the basement, I shut/drained the water
and removed the pressure reducer valve assembly. All seemed ok.
Also cleaned the dirt trap screen. Still the knocking continued.
Weeks later I got curious and pulled the valve again.
Something caught my eye this time. The brass valve seal washer cup had
shiny places on it. Looking into the valve seat I saw similar matching spots.
Turns out the washer was worn too thin and the metal parts were hammering
each other. A new (thicker) washer solved the mystery.
BTW, there was a bladder expansion tank installed.
Cheers, -=Dean=-
P.S.....Love this web site. Working on my garage & shop.