Noisy Pipes?


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Old 08-28-07, 06:58 AM
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Question Noisy Pipes?

We live in a 7 year old house. We have lived here for 4 years. For the first time about a month ago we started hearing what sounds like water pipes knocking. The sound usually (but not always) goes knock, knock, knock, creeeeeak. The sound seems to come from the interior basement wall behind our hot water heater where our main water turn-off is. The weird thing is this sound usually happens in the middle of the night WHEN THERE IS NO WATER RUNNING! The water heater is NOT filling, there are no toilet leaks, no water is running, but the pipes knock intermittently.

There is no knocking sound when we turn on/off any faucets or flush toilets, etc. so it doesn't seem like water hammer (which I've experienced before in previous houses and fixed by emptying the water lines).

Thanks for any ideas, we're completely stumped.
 
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Old 08-28-07, 11:33 AM
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sounds like a thermal expansion problem. it could be that when you hear the pipes knock, that is also when the heater is heating. the main problem could be that an insulator is missing or that a pipe is too close to a stud or a hole was drilled way to small and the pipe was forced though. all of these will creak if the pipes are expanding just a bit. you could try an expansion tank at the inlet of the water heater to see if it helps. make sure that the nipples on the water heater don't have check valves in them first though.
 
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Old 08-28-07, 03:00 PM
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We Have An Expansion Tank...

Thanks for the idea, although we have an expansion tank connected to the hot water heater (inlet line), so it must be something else. It actually sounds like two pipes knocking against each other and then one of them rubbing on wood. This happens when no water is running and the (natural gas) hot water heater is not heating (just the pilot light is on without the whole burner going). The weird thing is we never heard the problem in the previous 4 years we've been in the house, just this last month. If something worked itself loose, then why does it not knock all or most of the time?

Thanks for any more ideas, I really appreciate it.
 
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Old 08-28-07, 05:00 PM
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If this does this all the time, you coud experiment by turning off the pilot for one night. And do nothing different other than that. If problem goes away you know it is expansion issue.

Does expansion tank have air in it?
 
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Old 08-28-07, 09:09 PM
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Good Idea

Thanks for the idea. The expansion tank definitely could have air in it. I drained the hot water heater a few weeks before we started hearing the noise. What's the best way to get air out of the expansion tank? In the meantime, we'll try turning off the gas and pilot light to the hot water heater.
 
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Old 08-29-07, 07:01 AM
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It's Not Thermal Expansion

I turned off the pilot light last night and early this morning heard the same knocking noise. The pipes going into and out of the hot water tank were both cold to the touch. Any other thoughts are greatly appreciated. Thanks!
 
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Old 08-29-07, 10:52 AM
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you want air in the expansion tank so don't do anything if it's still inflated. it's basically a pressure type tank, with a rubber bladder to keep the air and water separate. it's the air that absorbs the expansion.
 
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Old 08-29-07, 03:28 PM
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Makes Sense

I thought that might be the case, after I posted my last message. It's hard to tell whether there's air in it or not, it has a rigid metal case so I can't tell if there's a bladder inside or if it's inflated or not. I suppose it doesn't matter since the knocking continues (once in a while, usually in the very early a.m.) even with the hot water heater off.
 
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Old 08-29-07, 04:45 PM
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You on city water or well. And how close is your nearest neighbor?
 
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Old 08-29-07, 08:37 PM
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City Water

We're connected to city water. We have a neighbor north of us about 60 feet away and another neighbor west of us about 100 feet.
 
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Old 09-12-07, 08:07 PM
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Solution, Maybe...

After doing some more reading and talking to someone in our city's Public Works department who said that excessive and variable water pressure is common in our neighborhood, I think the problem is that our Pressure Reducer Valve needs replacing. I'm going to purchase a pressure guage and test the pressure when the pipes start knocking again.

I'll probably need to hire a plumber to replace the valve, if that's the problem...
 
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Old 09-26-07, 07:06 AM
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Solution: New Pressure Reducing Valve

I didn't do this myself, but I hired a plumber to replace the Pressure Reducing Valve. Before, the water pressure in our pipes measured from 75-125psi. Now, it is set at a steady 50psi and best of all, NO KNOCKING PIPES!

The old pressure reducing valve was broken. The new one definitely does the job!
 
 

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