Water Pipe Knock

Fishin

My water pipe has a knocking sound only when I turn on the hot water. The hot water heater was replaced and still no effect. I have checked under the house and I am positive there are no loose pipes. I am on city water and the pressure seems fine. The house is 45 years old. I even tried a screw on water arrester but that had no effect. Any ideas? Thanks.

MgMopar

I think your water may be too hot. This is just an idea. I am thinking you may be getting bubbles in the hot water causing the noise in the pipes as it flows. I would try turning the temp down a bit on the heater if you think this is a possibility. Then try it again after it has cooled down a bit.


Here are a few questions that may help me and or other figure out what your noise is coming from )
Is it a steady knoking noise or more of a random rumble?
Is it louder in any areas of the home?
Does it change depending on were in the home you turn the water on?

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Mgmopar

Fishin

The water heater is gas and it is on low. The noise is from the same area all the time. Noise is the same no matter where the hot water is turned on. That would be kitchen sink, bath sink, shower and dishwasher. It is random but it starts as soon as the hot water is turned on. I would swear it would be an air pocket but it had to go away. Sounds much like a hammer hitting a 2x4.Thanks.

MgMopar

Hi Fishin

Here is my current best guess, based on what I have so far heard about your situation.
I have actually ran into a similar problem not to say that your is the same but it might be a place to start looking. I will try and explain the cause that I found and what we did to fix it.
A friend of mine had a town house and we would here a creeking/knocking noise in the wall going up o the second floor whenever hot water was used in the upper floor. This noise would last about 2-3 min after the water was started to be used. then it would stop even if hot water was used again. Wait quite a while and again it would do it when hot water was used.
What I found was the copper hot water feed for upstairs was strapped firmly to the 2x4's of the wall. When the hot water caused the pipe to expand it would creek against the wood as it was forced by the clamps. We had to open up the wall to find this but if it is a crawl or basement were the noise is it should be easier. We ended up using a different kind of strap made of a hard plastic and a thin piece of plastic between the wood when re-clamping it. This allowed the pipe to silently expand.
Like I said this may or may NOT be your problem but it is worth looking in to.:confused:

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Mgmopar

Fishin

Thanks Mopar. The next time I go to Lowes I will look for a plastic type clamp. I can get some thin plastic at work. I had added additional copper clamps and I think I even put some thin rubber in between the pipe and the joist. It is easy to get to, once I crawl under the house, so I will try something like that.Thanks for your response!

Fishin

Thanks Mopar. The next time I go to Lowes I will look for a plastic type clamp. I can get some thin plastic at work. I had added additional copper clamps and I think I even put some thin rubber in between the pipe and the joist in some areas. It is easy to get to, once I crawl under the house, so I will try something like that.Thanks for your response!

MgMopar

Hi

I would say get someone to run the hot water after you get into position under the crawl before installing your clamps and stuff. Maybe you will be able to hear or feel the location of the noise so you will know what area your trying to isolate. It might save you a couple trips down there. Bring your repair supplies with so you don't have to get back out

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Mgmopar