stubborn water hammer


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Old 06-06-07, 03:00 PM
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stubborn water hammer

I get water hammer intermittently from the toilets, dishwasher, and even the faucets. This sometimes happens when a valve is opened as well as when it is closed, both hot and cold water. The hot water tank is 2 years old. The only thing that stops the water hammer is shutting off the cold water supply to the hot water tank. Thinking it was a bad valve on the hot water side, I tried closing all the hot water shutoffs and opening the cold water supply to the tank and the hammer returned. Oh yeah....I tried an arrestor on one of the toilets and it made no difference. HELP!....thanks!
 
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Old 06-06-07, 03:27 PM
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oops...just want to add a bit more info. I changed the cold water shutoff valve to the tank, no help. And if I drain the tank and the pipes the problem seems better for a few hours or a day or so, and then returns. The pipes seem tight, though I can't check inside the walls. Given that there is no problem when the water supply to the hot water tank is shut off, is there anything in the tank itself that could cause this?? Thanks again!

Pete
 
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Old 06-07-07, 07:34 AM
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I hate to add frustration to the issue.....and possibly suggest something that may not work, but you can try adding a thermal expansion tank to the water heater.
 
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Old 06-07-07, 08:32 AM
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We just moved into a home that has one of those expansion tanks connected to the water heater.

The inspector mentioned that it prevented water hammer, but I have also heard it was to make sure there is enough water pressure from the water heater...

Not sure that helps, but should be researched as a possible solution. Would love to know what you find out.
 
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Old 06-07-07, 11:36 AM
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Inspectors...blah....they need to go back to school.

Actually it is there for pressure relief caused by thermal expansion in your water pipes. As a side effect it helps prevent the water hammer but isn't designed for that purpose. And it has nothing to do with the water pressure in your lines.
 
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Old 06-07-07, 12:42 PM
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Thanks. I appreciate the input. I've never actually seen one of those expansion tanks in use, and I'm not quite sure why I never needed one in any other house I lived in. I'll look into it though. Perhaps that would explain why draining the tank helps...because it takes a few hours to reheat after it's filled again. It's frustrating because it's intermittent, but today I noticed that the I could definitely feel the bang on the cold water supply line going into the tank and not on the hot output. I've read about some tanks using rubber check valves. Is it possible there is one on the input line and it is causing the problem? Thanks again for your thoughts. Much appreciated!

Pete
 
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Old 06-07-07, 04:36 PM
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Why you wouldn't have seen one before:

They didn't start using backflow prevention devices mainstream until about 10 years ago..least where i lilve. They also didn't go back and install a bunch on old houses..just on new houses. An older house may not have needed one because the system wasn't a 'closed' system where as a house built in the last decade is more likely to be on a closed system....
 
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Old 06-07-07, 05:07 PM
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Smile

Thanks! You're right....the manual for my hot water tank mentions the use of expansion tanks specifically on closed systems. My house is 20 years old and to my knowledge is not a closed system...just the original water meter on the main line.

I've seen this problem on other forums, but never a solution, so in case you're interested: Since I could feel the vibration on the cold water inlet, I removed the nipple from the inlet on the tank. I found it contained a plastic ball that acted as a one way check valve to prevent the heat from escaping up out of the tank. I didn't have another nipple so I just drove the ball out of the one I removed and reinstalled it. Voila! I'll give it a day or two to be sure, but it seems so much better already. I've read about those balls rattling, but in my case I think it was moving up and down so rapidly that it was stopping and starting the flow of water at a rate that produced water hammer. I've also read that some tanks use rubber flappers instead of balls but they may not be as effective. If my hammer is gone I'll try calling Whirlpool to see if they can offer another style that works without the negative side effects. Otherwise, it's back to the tried and true energy wasting days of the past. Thanks again!!
 
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Old 06-07-07, 05:15 PM
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My guess? You fixed the problem. Whenever i install heaters with those 'check valve' types in em i rip em out before installation because they cause that issue as well. Most plumbers do which is why i guess it never crossed my mind. You don't run into that much anymore.
 
 

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