Recently, we replaced the old galvanized pipe in out home with copper. When the hot-water is turned on in the tub we get a popping/banging sound that is most intense for the first minute or so that the water is running. The intensity of the noise decreases but continues for about 10-15 minutes after the hot-water is turned off. It may help to know that this is the longest hot-water run in the house. I have read elsewhere about water-hammer but am not sure this is the problem. It really sounds more like the expansion of the pipes due to the heat from the water. Am I right or is it something else? If I am right, how do I relieve this, loosen the clamps, etc?

Thanks for any advise.

A very long straight run with copper can expand 1/4 inches. Doesn't sound like much but it will cause lots of noise when it heats up. Additional clamping may help but could even make the noise loader. Any chance you can cut the pipe and add some left/right zig zags to the straight run. It would give the pipe room to move.

A very long straight run with copper can expand 1/4 inches. Doesn't sound like much but it will cause lots of noise when it heats up. Additional clamping may help but could even make the noise loader. Any chance you can cut the pipe and add some left/right zig zags to the straight run. It would give the pipe room to move.

For clarity, I would say that this run is probably around 30'. I can try some additional clamping and this may be the issue. I know that the run passes through/over a bathroom in the basement and there was very little room for clamping in this area due to the excessive amount of plumbing/electrical in this area. The house is built in such a way as nearly all of the plumbing is located in this area. I will check on the offsets. I believe that there is already one there, again due to the excess of goodies in the bathroom.

If I were to observe the popping while someone turned on the hot-water and try to feel where the pipes are moving the most I would assume that this would be a good place for a clamp. Does that sound right?

Thanks. Again.

Sounds like a good place to start. However, clamping is not going to stop the expansion, just the direction the pipe moves. It may not solve the problem but could lessen the noise.

Idd, At least clamp that straight run at both ends and every 10' in between. Another way to stop sidekick banging is to install pipe insulation. That should cover it. :D nm

[chuckles]
The clamping is the problem. [giggles] you put more clamps on this thing it will make more noise. When the pipes heat up they expand and contract. This causes the pipe to rub on the wood and squeek. To best remedy this put a small bit of insulation or tape or paper so the pipe does not rub.

Hi doug,

I agree with what you recommend in part. Unfortunately, clamping compliance is required in the UPC and I believe there is a mention of this also in the IRC. I am an old timer holdout because of the outgassing of plastic into standing water pipes that has been proven by lab testing. Pex can lobby and lie all they want but I will keep piping with copper. I have experienced that pipe creep can be stopped with insulation even when clamped with vinyl nailors or wire straps. Have you tried these yet? Nm

Wirez, that was my whole point

Idd, At least clamp that straight run at both ends and every 10' in between. Another way to stop sidekick banging is to install pipe insulation. That should cover it. :D nm

Hi again Idd,
I must add to this recommendation, any copper to galvy pipe will cause pipe leak erosion eventually. A dielectric union isolating the two pipe systems will inhibit the potential future leak problems. nm

wirez, that was my whole point

Sorry doug,
I must have misread part of your reply. I will work on my reading habits. Tx, nm

[chuckles]
the clamping is the problem. [giggles] you put more clamps on this thing it will make more noise. when the pipes heat up they expand and contract. this causes the pipe to rub on the wood and squeek. to best remedy this put a small bit of insulation or tape or paper so the pipe does not rub.

Does any type of insulation or tape work better. For example, masking tape, duct tape, electrical tape?

Also, I do have to say that this does not sound anything like a squeek. However, the clamps, which are 2-hole clamps, did seem a little tight. So I can see where your point might be correct yet with a different sound. If you had said that it might me that the popping sound I am hearing is the pipe disloging itself from the grip of the clamp as it expands I would definitely understand that.

Thanks to everyone who has posted so far.