"Moaning" pipes in new construction?

k9fanNovember 14, 2012

Ever since we moved back into our house after extensively remodeling it, including almost all new plumbing, we've noticed (especially at night, when other sounds are low), a frequent "moaning" that lasts a second or two at a time. It can be quite intrusive when the house is quiet. We haven't been able to identify the source or a trigger for the sound, but our best guess is that is has something to do with the water pipes. For the record, we have tankless water heaters (two) serving the house and a small apartment. The sound occurs even sometimes when there is no obvious water use going on, but we just don't know what else could be causing it.

We are quite surprised to have such a problem in a house with new plumbing. Is this a common/known problem in new construction? Is there something we can do to fix it, hopefully without tearing holes in the new walls? Thanks for any ideas.

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Thermal expansion of ductwork in the house can cause a moaning sound when the furnace kicks on and starts putting out warm air. This can happen when the duct is not properly mounted and is rubbing against a fixed structure or object. Isolating the exact location of the problem can be frustrating because you have to be looking at the right time, insulation can hide the problem location and the sound can echo through a large section of ducting.

    Bookmark   November 14, 2012 at 10:12AM
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Water pipes change size when the line is used, then slowly shrink back as they cool to ambient.

Hot water pipes are usually worse since the temperature swing is larger than the cold water line.

It takes a while for everything to come ot ambient since the water in the pipe AND the pipe both need to adjust their temperature.

'Moaning' type noises are often a pipe rubbing on a hole through a wood structural member.
Sharper noises can be the pipe stick/slipping over it hangers (especially plastic pipes since plastic has a higher coefficient of thermal expansion than metal pipes).

All you may need is a few turns of even paper (I prefer wax paper) where the pipe goes through a structural member or a holder.

Wrap it around the pipe about two turns than slide it into position so it is between the pipe and anything it is touching tightly or resting on.

It can be a rel PITA on finished work with pipes inside finished walls.

    Bookmark   November 14, 2012 at 11:23AM
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You don't live in Amityville, right?? ;)

    Bookmark   November 14, 2012 at 5:18PM
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Thanks for those replies. Nope, not Amityville :-)

It can't be the furnace, because this happens whether or not the furnace is in use. It even SEEMS to happen whether or not the water is in use, but perhaps the tankless heaters have their own ideas about when to turn on and off. The thing is, some days it seems to go on and on and others days we don't notice it, making it hard to bring in a professional to maybe deal with it.

Annoying to think that the builders didn't make sure to install the pipes in such a way as to avoid this problem (I hear it as I type this!) Well, maybe someday we'll stake out the basement and try to track down the locations ... hhough leaving the basement door open doesn't seem to make the sound any louder.

    Bookmark   November 15, 2012 at 8:34PM
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Water lines near duct-work or hydronic lines move as the air temperature around them changes.

    Bookmark   November 16, 2012 at 5:40PM
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