Pipes making knocking sound after flushing

I occasionally hear a fairly loud knocking sound in my pipes...like a hammer...after I flush either of the toilets in my house. Anyone have any idea what might cause that?
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The Amazing Exploding Arab wrote:

A couple of possibilities. It might just be that you need to partly close the valve to the toilet so it fills slower. It may also be water hammer and/or loose pipes.
If you can find the location of the noise, that would help.
If it is at the toilet, then try partly closing the shut off valve.
If it is the pipes themselves, and you can find the location, you can try securing them so they don't bang against what ever they are now hitting. You can also try adding or reactivating a anti-hammer device. That is likely to be in the wall, but you can try reactivating them by shutting off the water and opening up all the cold water valves. Try to make sure one of them is in the basement. You want to empty the pipes. That can empty at water hammer arrester and get it working again. Some designs fill with air after a time.
Beyond that I suggest from your question you will want to call a professional to recheck the cause of the problem and have them fix it. Adding an water hammer device can require some special skills.
It is also possible that it is a problem with the toilet itself. That would require replacing the valve inside the toilet. That is not a really difficult job if needed.
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Joseph E. Meehan

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Interesting response. When my basement toilet tank is filling I'll hear a soound not disimilar for a water pump (pipes banging?) and when I turn on the cold water valve on the basement sink there is a definite sound of banging coming from the water pipes somewhere.
What does an anti-hammer device look like? Can the banging cause cause damage to the pipes?
Mike

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Mike wrote:

Not usually, but it can damage some devices. Anti-hammer devices look like many different things. You can Google to find some images of commercial ones, but many homes have made on the spot devices. These look like an extension on the water line, past the last valve in a room and it ends with a vertical caped pipe located above the last device.
The idea is the rush of water in the pipe will slam against everything along the way when a valve is suddenly closed. Water does not compress so there is a sharp spike of water pressure causing the noise and possible damage. The water is compressible and absorbs the shock.
Commercial units may use things like rubber bladders with air in them to avoid the problem of the air being absorbed in the water and then the water filling the pipe eliminating the function, until someone drains the pipes to get the water out of it. These devices are almost always hidden behind the wall.

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Joseph E. Meehan

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Methinks the "water" in the last sentence should be changed to "air" as air IS comprressible and water ISN'T.
On Sat, 11 Sep 2004 09:38:21 GMT, "Joseph Meehan"

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snipped-for-privacy@vcoms.net wrote:

U is write. :-)

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Joseph E. Meehan

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On Sat, 11 Sep 2004 11:15:15 -0400, " snipped-for-privacy@vcoms.net"

Wow Dude.
Me thinks you got severe brain damage, or drain bamage because if you read what you said, your not making any sense. Get some help dude, and get off da crack before you post a message again !!!
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