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Runtal Radiator Corrosion - Help

MattVis Member Posts: 1
Hi and thanks for reading this.

I hired a contractor to install a boiler system with a mix of Runtal and Buderus panel radiators in 2016. The contractor ran non-oxygen barrier PEX for the supply and return lines by mistake and we didn't catch the error until a year later when the first Runtal failed. At that point the lines had been buried in closed cell insulation foam and all the finish work was done, drywall, etc. From speaking with Runtal support, they require the use of oxygen barrier PEX and apparently this has voided my warranty on the Runtal radiators.

In 2017 one of the welds at a supply thread failed on a Runtal and we lost a lot of boiler water on the floors. In 2020 my expansion tank developed a pin hole leak in the side and had to be swapped out. Yesterday I found a pin hole leak in the center of a radiator panel and upon closer inspection, I can see paint bubbling up all over all of the radiators. I sanded some of them down and it's rusty underneath.

Over the last 5 years I've tried to convince the contractor that the system is compromised by the use of the wrong PEX and they've taken some amount of responsibility; replacing the first radiator and doing yearly water testing for oxygen and adding chemicals. They keep assuring me that it isn't as bad as I think it is and that the chemicals are doing the job of scavenging oxygen, but the leaks are telling another story.

If you've worked with Runtal radiators before, is this consistent with what you'd expect in a system with non-oxygen barrier PEX?

Should I be concerned about the lifespan of the Buderus panel radiators? I talked to their tech support and they don't require barrier PEX, but said it "was a good idea".

Is the oxygen in the water going to be an issue for the cast iron pumps?

Are there any options for saving this system, short of replacing the PEX and/or the radiators?

I love these radiators and would hate to replace them with fin tube, but the thought of opening up everything again to replace the PEX is enough to make me consider it. I'd be interested in replacing the Runtals with more Buderus if I could be assured they wouldn't eventually fail.

thanks again for any advice. I appreciate it.



  • hot_rod
    hot_rod Member Posts: 22,142
    yes any ferrous metal in the system will corrode with ongoing O2. Hydronic chemicals can help, first they provide a thin protective coating on the metal, to protect from attack. Then the O2 scavengers should handle some ongoing ingress.
    The system needs to be cleaned well for the treatment chemicals to be able to do their job. Any oil or grease, flux, pipe dope left over will hamper the chemicals.

    I would get the test kit from the chemical provider so you could keep an eye on the treatment level.

    How often you need to boost depends on O2 ingress. The hotter you run the system the higher the rate of O2 permeation through the tube wall. Run the system on an outdoor reset control to keep supply temperatures to a minimum.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • MattVis
    MattVis Member Posts: 1
    thanks for the information Bob

    The testing is being done by the contractor at this point and they're telling me everything looks great, although components of the system keep failing. That makes me wonder.

    Do you happen to know of any labs that work directly with homeowners? I've looked around online and was unable to find anyone that would analyze single samples. They all were more geared towards industrial or commercial clients with lots of samples per year. Any recommendation would be appreciated.
  • Zman
    Zman Member Posts: 7,569
    Rhomar will test your water and provide recommendations.
    They will test an individual sample. I would fill in something for the company name is case they have an official policy of working with companies. They don't have a list of companies to compare.
    In your case, the "Commercial Analysis" would be a good choice so you can get an idea of how much metal is being eaten.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Derheatmeister
    Derheatmeister Member Posts: 1,542
    edited March 2021
    We have to deal with "Contractors" making this "Mistake" all of the time..
    If replacement of the tubing is not a option the following should be performed:
    1. Eliminating any ferrous Materials such as Boiler,Circlulating pumps,Expansion tanks,Fill valves,Air eliminators,flanges,Radiators and the replacement thereof for Brass,Bronze,Stainless Steel or other non ferrous materials.
    2. Reverse flushing the system.
    3. Installation of a Cleaner and allowing it to make contact with your system. In order to loosen up the FE debrie sometimes a special flushing machine should be utilized.
    4. Flushing of the Cleaner and making sure that no traces of the cleaner are left in the system.
    5. We use Deionized Water using a PREMIUM Mixed Resin Bed down to about 10 Microsiemens per CM as per VDI 2035.
    6. All this is in conjunction with a Sacrificial anode . Magnetic extraction of magnetite is also recommended.
    6. Annual check of the System fluid ,ON SITE within 15 minutes of extraction using a meter that has undergone a recent three point calibration measuring the following:PH,EC,TDS and Salinity. Total hardness, FE and CU should also be checked.
    7. Replacement of the Sacrificial anode if was consumed.
    8. Removal of Magnetite
    9. Installation of a Deionizing filter in the makeup line.
    I am surprised that Buderus would give you a "Green light" on such a install..
    Buderus Panel radiators are not made of Stainless Steel and can not be subjected to higher oxygen levels, They will eventually also fail and most likely cause trouble with other system components such as your Circulating pumps,expansion tanks and your Boiler.
    In my opinion Playing with Chemicals is for Chemist,not Plumbers or Heating Contractors.
    Finding the proper balance on O2 scavengers and the constant upkeep can be very challenging.
    I understand that changing the tube can be very intrusive, but if i had this situation in my home this would be my remedy towards this situation.
    Hope this helps :|
    Paul PolletsRich_49