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Can Viega Fostapex be connected to hydronic pex piping?

Radiant heat system was installed in my home, by my contractor's HVAC guy, combining Viega Fostapex & Pex. The coupler & connecter failed, flooding our basement with hot water. HVAC co. now out of business & I'm having a hard time finding someone that knows how to repair this system.


  • kcopp
    kcopp Member Posts: 4,188
    You should be able to do that. You will need to strip away that first layer. Then a standard sdr9 coupling will allow you to crimp on the coupling.
  • Ironman
    Ironman Member Posts: 7,119
    edited November 2018
    Or, you can use a combination of a male and female adaptor, one from each type of pipe that you're trying to join. Such as a male Fostapex joined to a female pex, or vise versa. It depends on what's available to you.

    Are you referring to where the pipe connects to the manifold?

    A pic or two of what you're dealing with would help.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.

  • hot_rod
    hot_rod Member Posts: 19,278
    Looks like a poor attempt to strip back the aluminum layer on the FostaPex? There is a factory tool to do that properly. Inside the pex is the same dimension as the HePex and any barbed coupling should work.

    I'm not a huge fan of those chinch ring rings.

    It's alway best to use the manufacturers connection, the FostaPex coupler would match the HePex and provide the best coupling, but you need Viega tools to crimp it properly.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Thank you for the replies. I'm told my system was installed incorrectly with too many connections, fostapex connected to pex & pex pipe going to to oil burner, (plumber said it should be copper off the burner).

    Apparently, there are several connections like this through the system, rather than home runs to air handler.
  • hot_rod
    hot_rod Member Posts: 19,278
    At the very least they should be using the Viega strip tool. I would rather see a Viega coupling used for the transition, I trust their stainless crimp cup best.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Paul Pollets
    Paul Pollets Member Posts: 3,620
    Use Viega fittings and crimp tools and stripper for best results. Otherwise, you'll likely have more leaks.
  • GroundUp
    GroundUp Member Posts: 1,573
    No problem connecting the two, but as was mentioned, that aluminum has not been stripped properly. The stripped pipe should be black in color. I too hate those cinch clamps, but they will hold if the joint has been prepped. Viega uses the stainless crimp collars which will also fit the pex