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Closed loop w/pex... need exp tank?

jim_59 Member Posts: 12
I've got a secondary closed loop that I heat with a wood fired boiler. The loop will get up to 190 degf and it's probably about 200' of 3/4" pex. I'm thinking I might not need an expansion tank because maybe the pex will expand as the pressure goes up. I this a reasonable design or should I put a tank in?


  • kevin coppinger_4
    kevin coppinger_4 Member Posts: 2,124
    Dan talks...

    about these twp guys who used to think out of the box w/ polybutylene and did not use an extrol tank years ago....that being said....the temp swings are so high in your case and the amount of water in the system...that makes it out of the question...put one in. kpc

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  • Brad White
    Brad White Member Posts: 2,398

    isolated body of water in a closed system needs an expansion tank and a relief valve.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Those two guys...

    were being experimental cheapskates, and the county no longer allows them to do stupid things like, not putting in expantion tanks, using water heaters as heat sources, nor allowing the combined use of potable and space heating water (legionairres generator).

    And their box of opportunity is quickly closing in other uncontrolled areas...:-)

    If it is non barrier tubing, they make stainless steel and phenolic lined tanks. Just make sure the air pressure is properly adjusted.

  • jim_59
    jim_59 Member Posts: 12
    Thanks for the recommendations.

  • jp_2
    jp_2 Member Posts: 1,935
    NOT thinking out of the box

    I wouldn't call that thinking out-of-the-box.

    Now if these guys calculated the expansion of pex of their system and found a direct correlation to the expansion of water in the system then you have thinking out of the box, I doubt that was the case.

    I still have not found an equation for DV/DT for water.

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