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Thread: Pressure tank and water hammer

  1. #1

    Default Pressure tank and water hammer

    My house is hooked up to rural water. The pressure of the water is about 82 psi. When we moved into the house, we notice some water hammer, but after a new dish washer was installed, it has gotten worse. Almost any fixture will cause the water hammer to some extend. I bought a small pressure tank and installed it where the water comes into the house. I was hoping this would solve the water hammer for the entire house. It didn't. The water comes in and goes to a water softner, then a hot water heater and so on. I've tried putting the pressure tank at different pressures to see if that changed anything and it didn't. Any advice on what to do? Is there a whole house solution or do I have to put an arrestor/air chamber on each faucet?

    Thanks
    Chris

  2. #2
    Master Plumber Redwood's Avatar
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    I would look towards making sure that pipes are adequately mounted and install hammer arrestors at the points of use that have the problem.

    The pressure tank is in the wrong location to absorb the water hammer...

    Kinda like if you bought a car and only got one bumper but had to choose where to mount it. So you decided to put it on the front but at the first light you get rear ended... Dang it didn't work!
    Last edited by Redwood; 04-06-2009 at 03:29 PM.

  3. #3

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    Quote Originally Posted by Redwood View Post
    Kinda like if you bought a car and only got one bumper but had to choose where to mount it. So you decided to put it on the front but at the first light you get rear ended... Dang it didn't work!
    How is it that this is the way all my projects go.....

    Thanks for the reply. I will look into arrestors on the worst faucets. Now I have to sift through the debate on air chambers vs purpose built arrestors.

    Later
    Chris

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    Master Plumber Redwood's Avatar
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    No debate there!
    Hammer Arrestors work, air chambers don't.

  5. #5
    Moderator valveman's Avatar
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    It is the velocity of water going through small pipes that causes the problem. When the toilet float valve or the dishwasher solenoid valve shut off, it causes water hammer when the velocity of the water is shut off abruptly. Just use the hose bib or shut off valve to choke back on how fast the toilet or washing machine fills. Reducing the velocity or how fast the machine fills, will keep water hammer from happening when the float or solenoid valve shuts off.

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    DIY Senior Member seaofnames's Avatar
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    Hammer arrestors for the win!

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    Forum Admin, Expert Plumber Terry's Avatar
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    Where I plumb, and quck closing valve gets them on a closed system.
    Adding a pressure reducer means you need hammer arrestor protection.
    Just dropping the pressure does not fix the water hammer.
    There are plenty of homes with 65 PSI with water hammer problems.
    Having a closed system is the problem.
    UPC Plumbing Code
    Hammer arrestors for:

    Washer
    Dishwasher
    Ice maker.

    It's a pretty simple fix.


    The one on the left is for a washer.
    The one in the center can be soldered onto a tee.
    The one on the right can be used inline like for a lav supply or an icemaker line.
    Last edited by Terry; 04-09-2009 at 09:10 AM.

  8. #8
    That's all folks! Gary Slusser's Avatar
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    If it was mine I'd install a PRV and set it to like 65 psi. That will slow down the water and prevent hammer.
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

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    Master Plumber Redwood's Avatar
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    Quote Originally Posted by Gary Slusser View Post
    If it was mine I'd install a PRV and set it to like 65 psi. That will slow down the water and prevent hammer.
    That is an excellent idea!
    Your pressure at 82 PSI is just a smidgion over the max of 80 PSI allowed in most plumbing codes.
    If you use a lazy hand gauge to record the high pressure over a 24 hour period you probably will find the pressure is boosted higher overnite as the water co. refills it's tanks and moves water around in the system.

    With the installation of a PRV a closed system is created and a thermal expansion tant should be added to the water heater inlet line between the valve and the tank.

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    DIY Junior Member vinbar's Avatar
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    Default vinbar

    Quote Originally Posted by valveman View Post
    It is the velocity of water going through small pipes that causes the problem. When the toilet float valve or the dishwasher solenoid valve shut off, it causes water hammer when the velocity of the water is shut off abruptly. Just use the hose bib or shut off valve to choke back on how fast the toilet or washing machine fills. Reducing the velocity or how fast the machine fills, will keep water hammer from happening when the float or solenoid valve shuts off.
    Is this a viable option for reducing water hammer at a washing machine? I have already installed hammer arrestors at the hose bibs but continue to get a thumping noise as the machine fills. The fill hoses jump quite noticeable as the solenoid on the washing machine opens and closes. This is something new since I bought a front load machine. Would installing an expansion tank help with water hammer? Thank you for your advice.

  11. #11
    That's all folks! Gary Slusser's Avatar
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    Then you need to reduce the pressure. Eighty two during the day can/will go higher as people/businesses on the system stop using water. Or install an arrestor at the washer.
    Last edited by Gary Slusser; 04-12-2009 at 10:03 AM.
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

  12. #12
    Forum Admin, Expert Plumber Terry's Avatar
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    The one on the left is for a washer.

    I don't install washer valves without the hammer arrestors anymore.
    If you have water hammer, you should install "hammer" arrestors.
    Expansion tanks don't do a thing for water hammer.
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    Last edited by Terry; 04-12-2009 at 11:34 AM.

  13. #13
    Master Plumber Redwood's Avatar
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    Terry, those Sioux Chief OX-Boxes with the hammer arrestors rock!
    On of my favorite plumbing products...


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