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Water Pipe Banging

Posted by mistopheles52 (My Page) on
Wed, Dec 16, 09 at 16:18

Hello all. This is a problem I would like to solve quickly as it will eventually drive me to insanity. When the 'HOT' water is on in the bathroom (beside the master bedroom) it starts making this weird banging noise in the wall. I tried an experiment and filled the sink up with hot water. The pipes do not bang....nothing happens until I drain the hot water and it starts running through the pipe. This is when the noise starts resonating louder and then it slowly stops after the water has gone through the pipe. Does anyone know what this is....it just started doing it and it is literally driving me crazy as my hubby starts running hot water at 5:45 am and then the noise starts. HELP Please!!


Follow-Up Postings:

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RE: Water Pipe Banging

How long and straight is the drain pipe below the sink until it leaves the house?


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RE: Water Pipe Banging

Baymee: I'm not sure what you mean? We are on city water.


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RE: Water Pipe Banging

The only thing I can think would be that water is dropping a long distance down a drain pipe.

The description of your concern doesn't make sense to me. Do you have some sort of addition to your piping behind the wall or under the sink, like a tempering valve?

Filling a sink wouldn't stop anything connected with your supply, but maybe with your drains.


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RE: Water Pipe Banging

Baymee: Thanks for replying. I just realized after reading original post that the noise does not appear under the sink but is in the wall oppositie the sink. The bathroom is not large. The sink is on one wall, the toilet beside it and then the bathtub. The noise is heard on the opposite wall at the end of the bathtub as you enter the bathroom. It baffles me (??) BTW, there is no addition of any sort and this just started recently.


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RE: Water Pipe Banging

The only other thing that might cause banging is steam in the line. Is the water excessively hot. Clueless on this one.


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RE: Water Pipe Banging

Two possible different issues- water hammer bangs pipes when a valve closes on the water supply line. Classic examples are washing machines which have solenoid valves that close very quickly. It's basically a shock wave as all that speeding water stops quickly. FWIW, this happens slightly at my place when we shut off the kitchen faucet (need to fix that).

That doesn't sound like what you're seeing, since it's only happening when you drain the sink, not when you shut off the water (even if you shut it off and wait 5sec or so). The other thing that could be going on is that you have a blocked vent stack and a tall column of water that's trying to pull a vacuum in the pipe and is making the drain line rattle.


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RE: Water Pipe Banging

I have 4 or 5 sounds of banging under the sink in the kitchen when i push the handle all the way up quickly. if i ease the handle up it does not do it. hot or cold direction does it equally.
when i shut the water off and turn it back on it doesn't make the banging noise. if i wait 15-30 minutes and turn on full force it does the banging again.


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RE: Water Pipe Banging

And you revived a thread from Dec 18, 09 instead of starting a new one why?


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RE: Water Pipe Banging

The problem you are describing is often called water hammer. Knocking pipes occur because the water supply pipes in your home are under pressure.This is required so your plumbing system can function. In addition to the pipes that carry the water, there are air chambers built into the pipes that cushion the pressure when you turn on the faucet.
The knocking occurs when the air in the pipes naturally depletes. When you turn on the faucet without the normal amount of air in the pockets, the water slams into the air or the end of the pipe, producing the dreaded knocking sound.


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