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New in floor build

Goos afternoon guys,

I have researched this to death I think and have learned a lot. Thanks for all the great free knowledge.

What I have is a 32x56x14 detached garage on an outdoor wood boiler. I live in SE Michigan where the winters go from mild to sub-zero. I have a 6" slab with above 1800' of 1/2 pex in it. The current setup is 1 zone with a plate exchanger and 1 pump. The question I know have is what do I fill it with? Soft water, Well water, distilled water, glycol, or no glycol? I'm so lost.

Thanks again and have a great weekend.


  • Ironman
    Ironman Member Posts: 6,695
    If it’s subject to freezing, I’d use a mixture of 40% glycol and 60% water minimum.

    As to the source of your water, that would depend upon its content.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • TurboStyleline
    TurboStyleline Member Posts: 2
    Thanks for the reply. Any idea what quality of water would be desired? PH level, dissolved solids, etc...
  • GroundUp
    GroundUp Member Posts: 1,311
    Did you install an air eliminator, expansion tank, and mixing valve between the heat exchanger and the pump? Pump must be located between the mixing valve and supply manifold. I too would recommend a propylene glycol solution, but 40+% is a little extreme unless it will be frozen regularly IMO. 30-35% will be sufficient for the occasional shutdown. It'd probably be best to buy pre-diluted inhibited glycol to the desired concentration and pump it in straight, that way the inhibitors will be proper for whatever dilution method was used.
  • hot_rod
    hot_rod Member Posts: 15,392
    You would need to know what is in your well water. Hydronic water should be below 7 gpg hardness, ph mid range TDS below 150 ppm

    If not bring in some deionized water to fill or blend glycols. Softened is better than. Extremely hard, but you add some chlorides and raise conductivity. Sometimes it is the lesser of two evils.

    On my detached garage I decided to skip glycol and run the pump continuously. I imagine your wood furnace is straight water?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream