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Do you need to install an expansion tank for my DHW?

maybemark
maybemark Member Posts: 1,131
I am reading the manuals for the Lochinvar whn and the squire tank, and in some of the plumbing schematic they only show one expansion tank for the system. When i read the squire it said you might need an expansion tank for the DHW tank.
How do you do it? And if you do it, i have a 40 gal tank, what size would i need?

Comments

  • Zman
    Zman Member Posts: 6,983
    Mark,
    You will need a small expansion tank if you have a check valve either at the meter or between the hot and cold side of your domestic water.
    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    maybemark
  • maybemark
    maybemark Member Posts: 1,131
    Carl
    thanks. I'm sorry about last week. I got out of hand, and i respected to hold off on questions until this week. I figured on not asking until I would hear from you.
    Thinking about it, i don't even have a meter, and there is no check valve at the moment between the hot and cold.
    Chicago is asking everyone that the city will instal meters, but I chose not to get one, and just have a flat rate
    It's nice to hear from you buddy, I really am sorry
    Mark
  • Gordy
    Gordy Member Posts: 9,514
    Like Carl said. The theory is that IF there is a back flow preventer at the meter the hot water expanding has no where to expand to but the house plumbing after the back flow preventer (check valve) . With out the check valve the expansion pressure would be able to transfer to the city supply piping.

    With out the x tank it can do damage to a tank water heater, and other components in the system. Just so you understand the reason Mark. It's all about heated water expanding, and needing a place to go just like a closed loop hot water heating system.
  • Gordy
    Gordy Member Posts: 9,514
    Tank size for water heater LET 2 for Potable water.
  • maybemark
    maybemark Member Posts: 1,131
    Gordy
    thanks teacher
    Mark
  • maybemark
    maybemark Member Posts: 1,131
    what does LET stand for? I imagine the 2 is 2 gallons
  • Gordy
    Gordy Member Posts: 9,514
    edited December 2014
    Just a 2 gal potable x tank is all need be. Tank psi set to city pressure. Fred should know.
  • maybemark
    maybemark Member Posts: 1,131
    thanks
  • RobG
    RobG Member Posts: 1,850
    edited December 2014
    You could also use a Watts Governor 80 on your toilet. It will discharge any overpressure into your sewer in the case of expansion.

    http://www.watts.com/pages/_products_details.asp?pid=7237
  • icesailor
    icesailor Member Posts: 7,265
    edited December 2014
    Expansion Tanks also protect closed systems from "Water Hammer" due to water momentum and check valve slamming shut.
  • maybemark
    maybemark Member Posts: 1,131
    thanks ice