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Old 04-07-2005, 10:01 AM   #1
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water hammer question


I have water hammer that only occurs when the hot water is running from any faucet or appliance (dishwasher, washing machine, etc.) and for a minute or so after it is turned off. It begins hammering somewhat rapidly (2-3 times per second) but it the interval between the hammers increases over time as the hot water continues to run. Eventually, after the water has ran for a few minutes, the sounds are far enough apart or eventually stop completely. Note that the pattern continues after I've turned the water off for a minute or so, at the same decreasing tempo. Also note that the tempo/hammering is cumulative; i.e., if I run the hot water for 30 seconds, shut it off for 15 seconds, and turn it back on, it continues at the same rate as before. If I leave the water off for several minutes, it resets back to the original rapid tempo.

Any ideas as to what is causing this and how to address it? Thanks!



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Old 04-09-2005, 10:30 PM   #2
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A classic reason for waterpipe hammer is air being trapped in the line. It is probably trapped in the highest point of your hot water piping system, otherwise it would have bled out from use. Find the highest point in the system and see if there is a way to bleed the air out, if there is none you will have to create one. That is a matter that you will have to give a bit more info on how your system is configured, and what it is made of, i.e., steel pipe, copper, or other...


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Old 04-11-2005, 09:12 PM   #3
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If you're handy, I'd put a little expansion tank in by the service entrance. Just cut in a 't' and hook up a small tank. Sometimes that bladder will obsorb enough of the hammer to make it go away. At any rate it's a cheap place to start. I bet you can find a coffee can size tank and parts for $50.
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Old 09-06-2005, 07:52 AM   #4
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I would try three diffrent things. One is going to the outlet of water that furthest away from your hot water tank and watwer main. Then turn both hot and cold water on. As you walk to the main turn all of your hot and cold water outlets on. Make sure the hot an cold water outlet in the lowest part of the house is on. Then shut the water main off. The pipes should begin to drain from air entering the pipes releasing you air pocket. Let the water drain until it stops. Oh, yeah this would be a good time to drain you hot water tank as well. Releasing, any type particles that might have settled at the bottom. After the water stops draining turn on the main leaving all water outlets open. If you drained the hot water tank let the water run until the tank is filled. because then the air in the hot water will be pused out as well. WHen you see that sink in lowest part of the hous stop spitting out air. Start there and begin shutting off the water out lets take your time. Because you do not want the air to get trapped again. So let the water push out the air. GO to the next nearest outlet shut it off, continue until you have turned all of the running water off. Let the hot water get hot and see what happens. This worked for me
If you have any type of water closets look in them. See if the pipe is just floating and not fasten. If so fasten it.
Last but not least and the most expensive put some of those knock things by each water outlet or where they are need
This went from cheap to expensive
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Old 09-07-2005, 12:13 AM   #5
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You can buy hammer arresters that simply screw onto the pipes that connect your washing machine. Hammer is usually caused by excess pressure or a loose washer. Change the washer in the offending faucet first, that's the cheapest/easiest. Good luck.
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Old 09-07-2005, 03:16 PM   #6
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This is an old thread, however do a search on water hammer. It has nothing to do with air in the lines! Those who give that advice should do their homework and research before misleading someone. It is great to be helpful but let's direct each other in the right direction!!
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Old 02-27-2006, 08:56 AM   #7
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have someone standing by the hot water tank hold their hand on both the cold water side and hotwater side.then turn on a faucet,if they feel viberation from either one then you need to rebrace the line.i had a customer complain about a noise after her washing machine was filled up.it would occur about two to three seconds after the water shut off.turns out it was the hotwater line from the hotwater tank causing the problem.
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Old 04-10-2006, 04:28 PM   #8
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you might need a water hammer arrestor. this site seems to have good quality and large selection of arrestors to help the issue you have going on. http://www.plumbersurplus.com/ProductList.aspx?Cat=240


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