dishwasher hammering

Why would a dishwasher make a hammering sound when filling? It severely shakes the copper fill pipe. Thx
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It could be that the valve is opening and closing rapidly causing water hammer.
That answers your question. Now I suppose you are going to ask:
Why would a dishwasher fill valve open and close rapidly?
Could be:
1 - A faulty fill valve 2 - A faulty float switch sending erroneous signals to the control board 3 - A faulty control board.
Cleaning the float switch would be my first suggestion.
Bench testing the valve would be my second (or test it in place with an external power supply if possible) I don't know how you would test the control board. Are there any diagnostics listed in the manual?
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On 2/5/2013 11:40, dumbstruck wrote:

Have you checked your water pressure? Ideally it should be around 50 PSI. If it's considerably higher you need a reducing valve on the main line.
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On Tuesday, February 5, 2013 5:36:19 PM UTC-10, Bob wrote:

Oh dear. It started when they raised our water pressure. From the scary sound, I took it as a sign to replace a severe kink in the feed pipe with a sharkbite, because i was warned here the kink would eventually leak. This went well for about a minute, then gave thunderous chattering.
Well, i have checked the float valve, and next will crank down the hot water valve down to near closed. I also may have pulled out a control wire when jamming the machine into its cubby hole. Yhanks all.
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On 2/5/2013 11:40, dumbstruck wrote:

Have you checked your water pressure? Ideally it should be around 50 PSI. If it's considerably higher you need a reducing valve on the main line.
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Does it do it only once each time when the water shuts off because it is sufficiently filled?
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wrote in message wrote:

Does it do it only once each time when the water shuts off because it is sufficiently filled?
***
Buy and install a water hammer arresting device as shown in this short video clip. I have one on my dishwasher and washing machine and it solved the problem.
http://youtu.be/vQf_qCYeeqs

http://youtu.be/vQf_qCYeeqs

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On Wednesday, February 6, 2013 1:04:54 PM UTC-10, snipped-for-privacy@sbcglobal.net wrote:

It make machine gun noises when filling, but not at other times. I did seem to hear the pipes filling at one point with no chattering. Our water pressure went up, but not to an unusual degree.
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On Wed, 6 Feb 2013 16:54:00 -0800 (PST), dumbstruck

Our water pressure went up, but not to an unusual degree.
You already said this started when they raised your water pressure, so you need to get a pressure regulator for the water source to that dishwasher. go to a plumbing supply place and get one. Problem solved!
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What would you consider a "usual degree"?
Have you checked the pressure before and after the pressure went up? If the pressure was already approaching the upper limit of what the fill valve was comfortable with, it wouldn't take much of an increase to cause problems.
When my PRV valve failed, I didn't really notice much difference in what came out of the faucets and showers, but the pipes would make a bump-bump-bump sound for a few seconds after any fixture was turned off. I put a pressure gauge on the utility sink and found that the pressure was above the normal range of 55 - 60 and approaching 80. As soon as I replaced the PRV, all the noise went away.
Head over to a hardware store and get one of these:
(Amazon.com product link shortened) I don't know if you have a PRV in your system, but you want to make sure that you test the pressure after the PRV, assuming the dishwasher is after the PRV, which it should be. My house has a hose spigot in the front and back that are at street pressure, so there's no sense in me testing the pressure there. I have a utility sink with a "hose connector faucet" that allows me check the pressure after the PRV.
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