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Open Loop Water Heater Leaking (With Non Oxygen Barrier PEX)

torgo Member Posts: 4
edited January 2023 in Radiant Heating
So. My water heater is leaking for my open loop radiant floor system. I've wanted to get it replaced to be closed loop for awhile since I am concerned about cross contamination with the potable water.

Call up a water heater replacement company. They are confused at my system.
Call up a radiant flooring company. We determine that I have non oxygen barrier pex and it shouldn't be used with a combi due to oxygen diffusion and rust. He is coming Wednesday though to give me options.

I just replaced my floors and painted my whole place. It doesn't seem to be an option to replace my PEX. And it doesn't seem an option to go to closed loop. So I am confused on what I should do. Stop using radiant floor and get minisplits or something? Unfortunately I don't have a lot of thinking time due to the leak (though small).


  • Larry Weingarten
    Larry Weingarten Member Posts: 3,304
    Hi, How much heat should the floors use hourly, in worst case (design day)? That number will help determine what sort of heat maker is appropriate.

    Yours, Larry
  • torgo
    torgo Member Posts: 4
    I dunno the flooring heat transfer characteristics.
    It's only two zone system. Probably 500 sqft of radiant flooring.
    Current water heater is gas, 65000 btu/hr, 49 gallon
  • kcopp
    kcopp Member Posts: 4,432
    edited January 2023
    You can use a combi boiler to do both.
    Make sure the combi mfg allows for non-barrier tubing in the system... I only know of one that allows.

    On the heat side make sure every part in the system has only brass, copper or stainless steel.
    No iron or steel.

    Add and maintain a good O2 inhibitor in the system.
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
    a flat plate heat exchanger and isolate the non barrier tubing from the system water. Like the Taco X-Block
  • GGross
    GGross Member Posts: 1,050
    Yeah I would use a flat plate heat exchanger to separate the new boiler from the non-barrier pex. That would be preferred. Most likely when your guy comes back that is what they will propose.