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Thread: waterhammer HELP

  1. #1
    DIY Junior Member pipe dr's Avatar
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    Default waterhammer HELP

    I am having a problem with water hammer or reverse hammer (i think) in my house. Every time I run my washing machine and the water is filling I get loud banging sounds like copper pipes are expanding and contracting (knocking i have installed water hammer arrestors on the washing machine hot and cold lines this has had no effect what so ever ). Also, every time I flush a toilet in the house I am getting a banging sound when its done filling and the valve shuts at the water heater (in the basement). I have tried everything (I have installed two water hammer arrestors at the highest point above the hot water tank in the basement, this has been no help). . the banging is also when i quickly shut off the kitchen tap I am out of ideas. Do I need an expansion tank somewhere in the line? Do I need more water hammer arrestors installed? any ideas ?

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    Do you know or have you checked to see what your water pressure is?

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    DIY Junior Member pipe dr's Avatar
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    its a 3 story house. what pressure should i be at ?

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    George the Plumber Gsalet's Avatar
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    What type shower valve do you have? sometimes debris gets in the check valve of a pressure balance shower valve and will cause this problem

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    DIY Junior Member pipe dr's Avatar
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    i have moen posi temps in all 3 bathrooms, the problems seem to have started when i got my new front load washer and dryer .

    would re piping the basement in worsbo help?
    Last edited by pipe dr; 11-03-2010 at 07:37 PM.

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    Forum Admin, Expert Plumber Terry's Avatar
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    Make sure the valves to those fixtures are open. A slightly closed valve, if there is a bad washer can cause some hammer.

    Like Cookie mentions, you may want to pick up a pressure gauge at the hardware store. Anything over 80 PSI needs reducing.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    I recently bought a new front-loader and it operates differently than the typical older top-loaders...it puts in a little water to check the weight and balance of the load, and then when operating, doesn't fill it all at once. As a result, it is turning the water on and off a lot compared with an older style. Same thing on the spin cycle, lots of on/off. For a water hammer arrester to work, it needs to be as close as possible to the offending valve that is causing the water to stop short when closing. If your water pressure is excessive, the water travels faster, and when it stops has more energy to cause the pipe to continue to move. If your water pressure exceeds 80psi, you should install a PRV and an expansion tank to drop it to a safe range. This might slow the velocity down enough to stop the water hammering. But, solonid operated valves generally should be installed with a hammer arrester in place as well.

    Last edited by Terry; 01-01-2011 at 09:59 AM.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Homeowner Thatguy's Avatar
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    Quote Originally Posted by pipe dr View Post
    its a 3 story house. what pressure should i be at ?
    WaCos have told me 20 PSI minimum, 40 PSI as a goal, 80 PSI is too much.

    Try page 32 of this link.
    http://www.rainbird.com/documents/di...atalog2009.pdf

    People who make products that must interface with city water are more forthcoming with info than the WaCos themselves. They are more motivated to have happy customers and they are more accountable for unhappy customers.
    I've had the PoCo, the TelCo and the GaCo "play games" with me.

    You can also use an engine compression gauge as a meter, with proper fittings. That's what I did.
    And your flowmeter is a clock and either the water meter or a large bucket of known volume.

    http://en.wikipedia.org/wiki/Water_hammer
    Last edited by Thatguy; 11-04-2010 at 03:19 PM.

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    DIY Junior Member pipe dr's Avatar
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    would installing worsbo help?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    If your pressure is excessive, fix that first. By worsbo, if you mean Wirsbo pex tubing, probably not, the pipe can continue to move around, but you may not hear it until it rubs on something enough to wear a hole in it.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Homeowner Thatguy's Avatar
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    Pex is 60x more elastic than copper but that may not be enough.

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    DIY Junior Member pipe dr's Avatar
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    would i be better to install 3/4' worsbo than 1/2'

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    Retired Defense Industry Engineer jadnashua's Avatar
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    It's Wirsbo, not worsbo, and water hammer should not be masked by repiping...solve the problem first. Excessive pressure makes it worse. Poorly anchored pipes do as well. True water hammer is the result of inertia of the moving water...when a valve closes quickly, that kinetic energy has to be dissipated somewhere, and it does that by continuing to move the pipes until they hit something. one way to absorb that is with an arrestor - a moving piston or air bladder. Even if you replaced all of the pipe with pex, the pex could and probably would bounce or whip around. This is not good! True, pex isn't hard like a hammer, so if it does hit something, it may not make as much noise, but it's still not good for it! So, check your water pressure; where the banging is worst, open the wall or look in the ceiling to see what it is hitting, and see if you can fix that. Put an engineered arrester as close as possible to each fast-acting valve, and if you water pressure is above 80psi, get and install a PRV and an expansion tank.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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