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Radiant heat loop

Hi guys,I just completed a 6000 square ft radiant heat job on a high end residential project.I have 4 separate manifolds with 8 supply lines ad 8 return lines all about 200 ft each.The manifolds are uponor all valved to purge each loop individually.

I have purged all of the three manifolds successfully but for the life of me,I can not not get the fourth one to go.I'm using two hoses, house pressure from a sill-cock in and the other one to purge it back out.

I tried again today but no luck.The drain  hose is still showing air after purging for over 15 minutes per loop.

Just wondering if any of you guys experienced anything like this.

Its really frustrating not to mention no heat for the home owner

All of the piping is 5/16 with the above floor track method.

                                                                                 Thanks for reading this.I'm at my wits end.



  • Harvey Ramer
    Harvey Ramer Member Posts: 2,239
    Have you

    purged out the boiler and distribution piping leading to the manifolds?

    Where would you go if you were air.
  • Ironman
    Ironman Member Posts: 7,376
    Test Pressure

    Did you keep air pressure on the loops while the floor was being put down? A tube could have been punctured.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Paul Pollets
    Paul Pollets Member Posts: 3,656

    The loops need to be purged one at a time at the manifold in question. Close return valve at manifold, close all loop ports and open one at a time until stream from purge valve is solid, with no air. When loop is purged, close it and do the next one. When all are purged, open all ports and open the return valve. 5/16 tubing tends to hold more air bubbles, probably due to capillary action of the smaller bore.
  • jackie c
    jackie c Member Posts: 7
    Radiant heat loop

    Thanks for all your replies.Yes i have done all of the above but to no avail.

    I think tomorrow ,i am going to swap out the manifold and up the pump size to a grundfos 26-009.The piping from the boiler to the manifold is perfectly warm and the mixing valve is doing its job.I really think its got something to do with the 5/16 piping and the manifold,I have purged each loop for at least 15 minutes each but can still see some air bubbles although not a lot.

    If that doesn't work i will have to try a purge pump of some sort.

    I will keep you guys posted.
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