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type of water to use in radiant floor

bradley Member Posts: 18
Hi.  I have a closed loop hydronic radiant system with a cast iron electric boiler.  I do not have an auto water feed.  My boiler manual says to treat the water if it is hard.  Would it be acceptable to used distilled water instead of using tap water and treating it?


  • Gordan
    Gordan Member Posts: 891
    edited February 2011
    Well... sure...

    But how are you going to pressurize it so you can fill the system with it?

    If you don't have a leak (and therefore don't have to constantly replenish with fresh water) the hard water shouldn't pose issues - there simply isn't enough mineral content to do harm. And if you have a leak, fix the leak. That's my opinion, anyway... others may differ.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    I use to say the same thing....

    And in most cases, it stands true, but a friends son in law sent me a report of the well water he'd used in his closed loop hydronic radiant floor heating system, and told me that his TT tank within a tank had completely plugged up, and the lower floors in the basement were completely closed off from the water.


    1,982 μS/cm

    Maximum recommended =800 μS/cm


    60 gpg

    Maximum recommended = 10.0 gpg

    Iron (Total)

    222 mg/l

    Maximum recommended level = 0.3 mg/l

    Iron (Ferric)

    170.2 mg/l

    Iron (Ferrous)

    51.8 mg/l


    33.6 mg/l

    Maximum recommended = 0.05 mg/l



    recommended range = 6.5-8.5

    Total Dissolved Solids (TDS)

    991 mg/l

    Maximum recommended = 500 mg/l

    The home is about 8 years old. It has a Vitodens boiler in it.

    Now, when someone asks me that water question, I give the only correct answer that can be given, that being "It Depends"

    Nasty water eh...


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  • Gordan
    Gordan Member Posts: 891
    And they drink that?!

    I hope they never need an MRI... could get messy!
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853

    They DON'T drink the water. Taste was the first indicator of a problem. They just purchased the house though Freddie Mac, who had taken the house back from the original purchaser. THe house was listed as having a good safe functioning well. Obviously, not safe. They are probably going to have to let Freddie Mac get it back because it is uninhabitable.



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  • bradley
    bradley Member Posts: 18
    filling system

    I haven't figured out how to fill the system, but there has to be a way.  Dan says not to rely on auto fill.  Any ideas?
  • Slimpickins
    Slimpickins Member Posts: 340
This discussion has been closed.