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CPVC pipes making clicking noise in attic after hot water used

Posted by geosulcata (My Page) on
Fri, Oct 26, 12 at 17:29

We live in FL and had our home repiped with CPVC after the copper lines in the slab leaked. The pipes make noise after hot water is used in the mornings...it clicks, like a dripping sound for 10 minutes after the water has stopped. This is in the summer. We had the plumber come back out and they loosened some of the straps. This provided quite a bit of improvement as the issue is only in the mornings now and not throughout the day as it was before. The issue, I think, is because the pipes travel so far. We have a one story house and the pipes are in the attic. It is the strapping, I believe, that is causing the pipes to make the "dripping" sound. It is VERY annoying to me, but it does not bother my husband (he is the one showering in the mornings while I am sleeping). The sound wakes me up. I would have gone with PEX had I known about the sound issue. The concern I have is the stress on the pipes/straps causing damage on the joints/connectors. Also, we are about to have insulation put in the attic, and I want to get this taken care of before hand. Is there anything that can be done? Also, when the children use the bathroom sink, it makes a harsh sound when they turn off the water. Would a hammer arrester (or whatever they are called) help? Can there be too many of those? There are none on the side of the house that has the clicking issue.


Follow-Up Postings:

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RE: CPVC pipes making clicking noise in attic after hot water use

CPVC has a much greater coefficient of expansion than do any of the metallic piping materials. It is going to move as the temperature changes-- period-- not a negotiable matter at all. So the installation MUST be designed to let the piping move without making noise, being damaged by the movement and not damaging anything else as result of the movement. And at the same time being supported per code. It is something that can be done. Long straight runs are not a good idea. Offsets help limit the movement in any section to very small amounts, by creating short straight runs.


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RE: CPVC pipes making clicking noise in attic after hot water use

Would putting insulating pipe wrap on the pipes help in keeping the rise and fall of the temperature of the pipes to be more gradual thereby negating the noise?


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RE: CPVC pipes making clicking noise in attic after hot water use

The coefficient of expansion is different for each size of pipe, but for illustration let us consider 3/4" CPVC.

For 3/4" CPVC the expansion is 1" per 100' of pipe for every 1degF of temperature change.

Assuming the pipe begins at an ambient temp of 70 degress when you start your shower and the hot water is set for the code max of 125 degF the temperature differential in the pipe would be 125-70 = 55degF.

The thermal expansion would then be 55" per 100ft of pipe.

We rarely see a run of pipe longer than 50' in a residential system, but even at 50ft the thermal expansion would be 27.5".

The CPVC installation handbook suggests a 18" expansion loop at every 30' on a straight run and the loop should be located near the center of the run.

To make the expansion loop the pipe is cut and a 90deg elbow is installed. The line is then stubbed out 18" and a 90deg elbow is installed. A short 4 to 6" length of tubing to another 90deg elbow turning back towards the original pipe and then connect the loop to the original pipe with another 90deg elbow. On the ends where the pipe drops down through holes the pipe should be run about 18" to one side of the hole with an 18" offset from the pipe to the hole. IN this manner as the pipe expands the 18" horizontal offsets can flex slightly to absorb the expansion.

Insulating the pipe will not prevent the expansion because the temperature differential results from the temp of the liquid in the pipe, however if the pipe is first insulated, then pipe hangers large enough to fit the exterior of the pipe insulation are installed, the pipe is free to move slightly within the insulation.

If you have your water lines run through the attic space you definitely want the cold water lines insulated, otherwise as the pipe cools from the cold water moisture will condensate on the pipe and drip down on your ceiling causing water damage the same as a leak.


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