Click here to Find a Contractor in your area.
In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Need to contact us? Visit

Gunk in the Onix

Hello folks I've been tasked with removing antifreeze from a staple up radiant floor. The tubing used is Onyx. Now I haven't started this yet but from some past experience I've found black gunk in the systems where Onyx has been used. I would like to know if there is any thing I can use to "clean" this and or neutralize the spread of the gunk?

thanks for any advice.



  • kcoppkcopp Member Posts: 2,744
    edited February 2013

    Glycol in Onix is bad news... I had one system it killed the tubing. Rohmar products work well for me. I have another system in town that I flushed out as much crap w/ water at street pressure. Then added the 9100 and ran it in the system for a month. Flushed out the crap (looked like black coffee) and then added the 922. It has run that way for 9 mo. It should have a check up in the spring... good luck.
  • BobAlsBobAls Member Posts: 7
    Onix and Glycol seem OK to us.

    We've never actually seen the mysterious "gunk" in Onix tubing with glycol. As a safeguard I add only distilled water to the glycol mixture, and because they are usually closed sytems, a feeder system (such as an Axiom) is added to maintain the pressure and fluid balance. So is the gunk "really" a problem with the Onix, or is it based on the on-site water condition?

    Any ideas?

  • Matthew GrallertMatthew Grallert Member Posts: 109
    Gunk, Onyx and Glycol

    Thanks a bunch for the reply kcopp. This could be a silly question but here goes, are 9100 and 922 rohmar products? Ill look Rohmar up my self just thought i'd ask. And yes unfortunately there is glycol in the system. Been there for about five years. Fingers crossed.

    Thanks again for the input.


  • BobAlsBobAls Member Posts: 7
    Heatway or Onix ?....age of tubes.

    Just another quick question. How old is the tubing in the house? Is it actually Onix (which is black) or is it Heatway (which is usually tannish)? The older Heatway stuff had all kinds of problems, really wasn't great stuff. The newer Onix seems OK.
  • SWEISWEI Member Posts: 7,356
    9100 & 922

    Both come from Rhomar.  Good stuff.
  • Matthew GrallertMatthew Grallert Member Posts: 109

    Bob it's Onix. Black. I remember the Heatway orange tubing. Lots of issues. I run across it sometimes and when I do I suggest isolating it from the system with a HX of some kind.

  • kcoppkcopp Member Posts: 2,744
    RE..Onix and Glycol...

    If you are taking all the precautions to add distilled water to a heating system then you are most likely flushing and cleaning the system before you add the Propylene glycol and Distilled water... You are to be commended! Most people don't do that and therefore the crap in the system kill the oxygen inhibitors in the mix in short order. The system then goes acidic sooner and attacks the tubing. As a general rule I don't think a lot of contractors pay much attention to boiler system chemistry and that is a shame.
This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!