Thermal Expantion Tank vs Thermal Expansion Relief Valve?

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

  1. Grayfeathers

    Grayfeathers New Member

    Messages:
    27
    Location:
    Pleasant Grove, Alabama
    The Water Works dept. has decided to redo our water mains and install new water meters with a duel-check backflow preventer. The Water Works dept. has requested that the private owner install, or should I say have a professional install a Thermal Expansion relief device. They have suggested either a TE Relief Ball Cock, a TE Tank or a TE Relief Valve. I need some opinions as to what is best to have installed. I'm not planning on being in my house much longer (trying to sell) but I want to make sure that what is installed is up to code and will do the job.

    Thanks so much in advance.
  2. Redwood

    Redwood Master Plumber

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    Location:
    Connecticut
  3. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL
    I would opt for the expansion tank myself.
  4. Gary Swart

    Gary Swart In the Trades

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    Location:
    Yakima WA
    I'm not a pro so there are things I am not aware of. That said, the topic of thermal expansion comes up frequently on this forum. The only way I am familiar with is the thermal expansion tank as pictured in the previous post. These are used when the home has a closed system. A closed system is created when either a pressure regulator valve is installed or a meter with a check valve such as you describe. What happens is as we all know when water heats, it expands. If the system is open, the expansion is absorbed by the city water main. However, when the system is closed, there is no place for the expansion to go, so it will trip the T/P valve on the water heater. The thermal expansion tank is installed in the cold water intake between the PRV or check valve and the water heater. It is air charged to equal the house water pressure and will absorb this expansion. It is really a small volume of water that has to be absorbed, but with the tank, pressure in the water heater will rise rapidly and will exceed the 150 psi that the T/P is designed for. Installation is quite simple, it requires a tee in the cold water line to which the screw adapter is soldered. The tank screws on to the adapter. The tank does have to be very well supported. Tanks cost around $50 and come in at least 2 sizes to best fit the home. You will have to do this if the meter change is made while you are in the home, the T/P will immediately trip once the system is closed and the heater turns on.
  5. cwhyu2

    cwhyu2 Consultant

    Messages:
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    Location:
    Cincinnati OH
    Yes the expansion tank is the way to go .
  6. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    A tank is the way to go...
  7. FloridaOrange

    FloridaOrange Plumbing Designer

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    1,317
    Location:
    SW Florida

    Just to add to your post. Expansion tanks can also help when you have a check valve/backflow preventer and there is fluctuation in pressure on the city side. Your system can experience higher pressure that cannot be relieved back into the city main.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,292
    Location:
    Cave Creek, Arizona
    Te

    A thermal expansion ballcock is the least expensive solution. It will work until someone replaces the ballcock with a standard one.
  9. Grayfeathers

    Grayfeathers New Member

    Messages:
    27
    Location:
    Pleasant Grove, Alabama
    Thanks for all the respnses

    I'll look into getting a Thermal Expansion Tank. Sounds like it's the way to go. I'll probably do it right and get a professional in here and do the job.

    Thanks again for all your help guys.
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