thermal expansion tank for water heater?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by scrappy, Mar 10, 2007.

  1. scrappy

    scrappy New Member

    Mar 10, 2007
    New York
    do i need to add a thermal expansion tank to my new hot water heater? old one was 50 gall electric and did not have one. new tank is 80 gall electric?
  2. Randyj

    Randyj Master Plumber

    Nov 25, 2006
    I've seen very few old houses that actually had them. It is recommended for any closed system. Since most modern water supplies have a check valves to prevent water from flowing back into the public water system it is highly recommended.
  3. Sponsor

    Sponsor Paid Advertisement

  4. Gary Swart

    Gary Swart In the Trades

    Sep 1, 2004
    Yakima WA
    When water heats it expands. Unless there is a check valve in the intake supply line, this expansion is absorbed by the water main. Some city meters have a check valve built in, and a pressure regulator valve also is a check valve. It either of these are present, then you have what is termed a closed system. Without an expansion tank in a closed system, the expanded water creates a huge pressure rise in the water heater and results in the TP valve tripping. The size of the tank would not make any difference, so it sounds like you do not have a closed system and do not need an expansion tank.
Similar Threads: thermal expansion
Forum Title Date
Plumbing Forum, Professional & DIY Advice Thermal expansion tank Dec 22, 2016
Plumbing Forum, Professional & DIY Advice Thermal Expansion Valve -- in Toilet! Jul 9, 2015
Plumbing Forum, Professional & DIY Advice Thermal Expansion Feb 7, 2014
Plumbing Forum, Professional & DIY Advice Dripping thermal expansion relief value Oct 22, 2013
Plumbing Forum, Professional & DIY Advice thoughts on thermal expansion tanks Mar 20, 2013

Share This Page