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Runtal UF-2 Radiator Rusting from inside out

haukeghaukeg Posts: 23Member
edited March 12 in Radiant Heating
I have a radiant in floor PEX heating setup on my main floor, however the bonehead installer (who quickly went out of business) installed non-oxygen barrier PEX, so my system has been plagued with corrosion issues over the years. I had to replace my boiler to deal with the rust as well as oxygen removing components in the plumbing. However, the installer that fixed me up said eventually my Runtal Baseboards (in the basement) would “pit” out with rust from within, since they are not meant to be used with oxygen rich water.

Well, the day has come (see photo link below). So I’m starting to investigate options to replacement. It looks like from brief searching (nothing thorough yet), Slant Fin may be an option. Some literature I read on the Fine Line series said it had “rust resistant” from galvanized enclosures, but I’m not certain that isn’t just the cover. Anyhow, looking for any leads or advice on options. Thanks!

photo of rust & radiator


  • Danny ScullyDanny Scully Posts: 1,153Member
    That’s just the cover @haukeg. You need to address that non-barrier piping. Either abandon it or isolate it with its own heat exchanger.
  • kcoppkcopp Posts: 3,324Member
    I have a home out there w/ the exact situation.... Polybutylene non barrier tubing and Runtal rads. One by one they have been clogging and pin holing away. HX is out of the question as the radiators cant be isolated. I have power flushed and been adding Fernox on a yearly basis.
    High output Baseboard would be a decent alternative as its copper.
    I would try to pull as much of the tubing out of the system as possible.
  • Paul PolletsPaul Pollets Posts: 3,169Member
    Radiators don't need to be isolated to install a HX on the boiler. If the non-barrier tubing isn't dealt with, there will be continuous failure of any ferrous components.
  • haukeghaukeg Posts: 23Member
    @Danny Scully - any idea how that could happen to just the cover. I’m assuming from your comment water is not going through that part?
    @kcopp How has the Fernox worked for you, has it helped? Any suggestion on high output baseboard models/makes?
    @Paul Pollets I hear you on dealing with the pex, but it’s hard to say how/if I can effectively, would have to tear all ceiling drywall/insulation out in my finished basement to do so, so I’ve done the best with what I can to make it work. It’s a bitch of a problem. Any suggestions for trying to make it work, this is why I’ve been looking for non-ferrous baseboard rads to help avoid the full pex replcement.

    Thanks guys, appreciate the replies.
  • BrewbeerBrewbeer Posts: 575Member
    Copper fin tube baseboards, lots of options to choose from. Do a room by room heat loss calc and size your new baseboards accordingly. I used Sterling Heat Trim Plus in my recent project.

    Don't dismiss cutting the basement ceiling drywall, it's a really good option.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread:
    System Photo:
  • Danny ScullyDanny Scully Posts: 1,153Member
    @haukeg I was referring to the rust resistant Slant/Fin. That’s the enclosure only not the actually heating element. If the radiant zone is the only zone that non-barrier tubing was used than a heat exchanger is an option. If, however, I’m misunderstanding you and the non-barrier tubing is connected directly to the baseboard, than a heat exchanger is not an option.
  • haukeghaukeg Posts: 23Member
    edited March 13
    @Danny Scully Ah, I see, thanks - I assumed you looked at my photo and determined it was a cover. I believe it's my fear, rust from insider the radiant cavity. Yes, unfortunately the tubing for both in-floor and to the wall mounted baseboards is non-barrier. :(
    @Brewbeer thanks for the tip. On the ceiling, not sure what you mean by "a good option," it's a pretty massive undertaking financially and from a mess/life impact. I've been there before, when we had this bunk pex installed 10 years ago, so I am a bit afraid of reopening and dealing with all new pex runs. Wondering what the long term trade off really is if I got new copper baseboards etc...

  • kcoppkcopp Posts: 3,324Member
    The Fernox certainly helps. The chemistry is something you need to pay attention to. In your case I would clean/ powerflush the system to get as much of the junk out of there. Fill w/ a de-mineralized water and treat.
    As to the baseboard... I like the Sterling Senior. Petite 9 is also good.
  • SuperTechSuperTech Posts: 938Member
    edited March 13
    It might not be a bad idea to consider replacing the Runtal with PEX radiant baseboards. Being able to operate the system at lower temperature would help slow the oxygen ingress. An outdoor reset control would be a good idea.
  • BrewbeerBrewbeer Posts: 575Member
    @haukeg I used that phrase because if you have time and DIY skills, drywall repair is really, really cheap. AND you'd get to install the correct piping this time around and never worry about it again. AND you might be able to save some of the radiators you have that still work.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread:
    System Photo:
  • haukeghaukeg Posts: 23Member
    edited March 14
    @Brewbeer thanks, I hear you, I’ve thought a lot about it. You may be right, but the mess and time is the challenge. Appreciate the point tho.
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