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fresh water system

Discussion in 'Post Yacht' started by about time, Jan 13, 2015.

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  1. about time

    about time Member

    Joined:
    Oct 17, 2009
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    109
    Location:
    ponce inlet fl
    I am looking for suggestions. I am experiencing a "pressure bang" in my fresh water system. When my dish washer or washer dryer goes through their cycles a water "knock" occurs. I am concerned that eventually damage will occur to my system, I have copper lines. Not to mention it irritates me. I know in a house the solution is to dead end a leg and trap air in a coil of copper tubing. I don't think that is practical for a boat. I have an expansion tank in the 12v boat side of the system, when I am using dock water a pressure valve closes and excludes the expansion tank from the system. I am aware of the potential disadvantages of using dockside pressure, and try to be diligent turning it off when no one is aboard.
    Will my expansion tank handle the 60 psi from the dock, if so I can replumb the system to include it on the dockside. Should I purchase another expansion tank that will tolerate the pressure, or is there a simpler solution?
  2. Pascal

    Pascal Senior Member

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    Feb 29, 2008
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    Miami, FL
    Usually most expansion tanks are rated to handle pressure from water pumps which is has high as regulated dockside pressure.
  3. Capt J

    Capt J Senior Member

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    Fort Lauderdale
    I agree, expansion tanks should be rated for dockside pressure and should be in the system when connected to the dock.
  4. Eroc

    Eroc Member

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    Apr 8, 2010
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    Location:
    CT
    You definitely need to run an expansion tank, most tank manufacturers have a max working pressure of at least 100psi. Not sure what you have currently but Amtrol is hands down the best if your looking into another
  5. dennismc

    dennismc Senior Member

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    1,175
    Location:
    Vancouver BC
    These appliances usually have a fast closing solenoid valve on the water supply, this will cause water hammer, if the exp tk is too far from the appliance then the tank may be ineffective, if it persists it can cause pipe rupture, a manufactured water hammer arrestor is the best fix, s/b available at local hardware, they are sized to suit the appliance served.
  6. about time

    about time Member

    Joined:
    Oct 17, 2009
    Messages:
    109
    Location:
    ponce inlet fl
    Thank you,
    Googled water hammer arrestor, will decide which one works best for my application. Did not know they existed. Exactly what I was looking for.
  7. mikewheels

    mikewheels New Member

    Joined:
    Feb 10, 2012
    Messages:
    25
    Location:
    North West Palm area
    Another possible solution is to put a pressure regulator on the hose end when using dock side water. I bought one at West Marine and this does reduce the pressure considerably. I wanted to reduce the water pressure on my older water lines.