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Radiant Manifold Supply & Return

I'm installing a manifold in a new construction house and am curious if it is generally acceptable to route the supply and return through the concrete slab.


  • STEVEusaPA
    STEVEusaPA Member Posts: 5,689
    If you mean the supply and return to/from the boiler, I wouldn't if you could avoid it.
  • I've done it before with PEX. It can save a lot of time and materials, but if it ever goes bad, it can be very expensive to re-route. I'd do it again and leave a good five feet of tubing exposed at either end.

    Consider that the below ground tubing is protected from exposure to physical damage and UV light.
    Often wrong, never in doubt.
  • GroundUp
    GroundUp Member Posts: 1,406
    The manifold is going to be mounted in a different room than the boiler and you want to run lines between the two rooms? Assuming this is a radiant slab, of course it's okay to embed PEX mains in the slab for a remote manifold. The entire heating system is pex otherwise- if the mains are going to "go bad", so are the floor loops. It's a good idea to insulate the mains so the heat gets where it's supposed to be (the manifold) instead of between the two locations, but as far as embedding it in the slab, absolutely. It's done every day.
  • Zman
    Zman Member Posts: 7,330
    It is done all the time. Insulating them is a good idea.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • tdfontaine
    tdfontaine Member Posts: 5
    I should have clarified from my original post but I was talking about a manifold that is piped as a secondary loop. Unfortunately I was not able to insulate the supply/return before the concrete slab was placed...hopefully I don't regret it later.

    Thank you all for the input!
  • Retired_guy
    Retired_guy Member Posts: 6
    As you suspect, there will likely be excessive radiated heating following those line back to the loop.
  • Paul Pollets
    Paul Pollets Member Posts: 3,509
    It's too late now, but it's preferred to run the S&R 6" under the slab pour, using 3/4" insulation. This prevents the piping from shedding BTU's on its way to the manifold. It also reduces stresses on the piping and a potential "hot spot" striping on the slab. Your method will work, and hopefully the tubing is at least 11/4" under the top of slab.