Pressure tank and water hammer

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by Chris611, Apr 6, 2009.

  1. Chris611

    Chris611 New Member

    Messages:
    2
    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. Redwood

    Redwood Master Plumber

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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: Apr 6, 2009
  3. Chris611

    Chris611 New Member

    Messages:
    2
    How is it that this is the way all my projects go.....:D

    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
  4. Redwood

    Redwood Master Plumber

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    No debate there!
    Hammer Arrestors work, air chambers don't.
  5. valveman

    valveman Moderator Staff Member

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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.
  6. seaofnames

    seaofnames DIY Senior Member

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    Hammer arrestors for the win!
  7. Terry

    Terry Administrator Staff Member

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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.

    [​IMG]
    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: Apr 9, 2009
  8. Gary Slusser

    Gary Slusser That's all folks!

    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.
  9. Redwood

    Redwood Master Plumber

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    Location:
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    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.
  10. vinbar

    vinbar New Member

    Messages:
    3
    Location:
    Victoria, British Columbia
    vinbar

    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. Gary Slusser

    Gary Slusser That's all folks!

    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: Apr 12, 2009
  12. Terry

    Terry Administrator Staff Member

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    Location:
    Bothell, Washington
    [​IMG]
    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.

    [​IMG]

    Or a box with shutoffs

    Attached Files:

    Last edited: Sep 13, 2014
  13. Redwood

    Redwood Master Plumber

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    Location:
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    Terry, those Sioux Chief OX-Boxes with the hammer arrestors rock!
    On of my favorite plumbing products...

    [​IMG]
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