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Watts Onix radiant heating tubing system

bob eck
bob eck Member Posts: 930
Anyone installing the Watts Onix radiant tubing system.
Customer looking at using this tubing for a radiant heating job on a staple up system.
I know when using Viega pex tubing on a staple up job they recommend using aluminum heat transfer sheets.
Are aluminum heat transfer sheets needed with the Watts Onix tubing?
Any drawbacks to using Watts Onix radiant pex tubing?


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    I wouldn't do it (staple up) with ANY tube. Most smart manufacturers are getting away from staple up due to inherent baggage it brings to the game.

    As for Onix, although it does have a metallic (mylar) oxygen barrier, each place where the tubing is cut to place the tube on a manifold represents a parallel path for oxygen to diffuse into the system fluid. I am hearing from a lot of people in the field that their ferrous components are dissolving on systems with this tubing in it. In order for it to have a good conductive "bite" on the subfloor, it requires being stapled about every 6", and they prefer that the tubing be just a little distorted to provide a better surface contact between the hose and the floor. This distortion also equates to higher pressure drop on flow due to all of the occlusions into the flow stream.

    If he has no option but to do it from below the floor, I'd STRONGLY recommend the use of EXTRUDED aluminum heat transmission plates.

    The baggage that comes with staple up is noise, higher temperatures of operation, and trans zone heat flow in certain situations. Even applying a good ODR will not completely negate the noise issues.

    Proceed with caution.


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  • hot_rod
    hot_rod Member Posts: 22,261
    What Mark said. I'd look closely at the loads in each area to determine if staple up can work adequately.

    Transfer plates add not only better transfer, but more consistent floor surface temperature, and lower operating temperatures.

    I had to go around again this season and tweak all my rubber tube barb clamps, they tend to seep every few years me. I used 3/4 rubber to run to my remote manifolds and a few thin slab areas.

    Radiant Design and Supply in Bozeman has a nice on top system. They design, and provide the layout and supply the plates and return bends, you buy the plywood locally for the filler strips, and your choice of PEX. Saves the cost of shipping plywood across the nation.

    Getting the tube and plates close to the final finished flooring speeds performance and allows for lowest SWT.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream