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Thread: Need Suggestions please....Clogged Heat lines.....

  1. #1

    Default Need Suggestions please....Clogged Heat lines.....

    During a recent bathroom addition, I installed a new section of baseboard heat. When I purged the system and bled the air through the bleeder valve I wasn't getting the heat to circulate. I decided to install a purge set up on the loop for the new bathroom (this is a monoflow system or aome call a venturi system. When I Cut out the old return side (black iron pipe) it was packed solid with debris, sludge and rust. I also noticed off the main supply and return the are not producing much heat. I can not get water through the new purge set up because of the blocked pipes. What is recommended here? New heating system piping? That is what I think. Any suggestions? Thanks.

  2. #2
    In the trades Dana's Avatar
    Join Date
    Jan 2009


    This sounds like steam to hydronic conversion at some point in it's history?

    There's no restoring the flow capacity of corroded up iron- it's done. Ideally you could pull the old pipe and be rid of it to use the same chases & holes to snake in some PEX, but there are few cases where that's easy to do. If this is a DIY weekender project, wait until the heating season is over- this could take some time. Oxygen barrier PEX will be nicer to any remaining iron in the system (like iron pumps & boilers) than the cheapest stuff, and will be far easier/cheaper/quicker to retrofit through walls & plumbing chases than sweat copper, etc. If you've been running the system at 180F or higher you'll have to back it off a bit to use PEX (but with the higher flow it'll likely still deliver the heat at 150-160F that it was at a 180F trickle.) If you can, insulate any of the new pipe as you go with 3/4"-wall closed cell pipe insulation wherever it goes through unconditioned or semi-conditioned space like unfinished basements/crawlspaces/attics. (Don't us the cheapo 3/8" wall stuff available at box stores- order it online if you can't find it at your local supply houses. Grainger carries some.)

  3. #3


    OK, so the repipe is in order now. So, what I need is to do some research. Is it possible to keep the old radiators and seperate each bedroom into seperate zones as you would in a newer baseboard loop system? Can you put zone valves on each supply to their respective room? It seems it may work, but I am not sure. Can you eliminate the "supply and return" system and include the existing radiators on a more common loop system, one loop for each zone as you would with a typical hot water baseboard system? Just some questions. I would really like to help my customer out the best way I can. They are not totally opposed to getting rid of the old radiators however, they would much prefer to keep them. Thanks

  4. #4
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona


    The logical question to ask is, "Where did this stuff come from?" A heating system is a closed system so the only thing introduced into it is occassional water to make up for possible loss, and anything in that water should stay in the boiler. The water itself becomes inert, which is why heating systems can use black steel pipe without concerns about it "rusting". Radiators do not respond well to a loop system, and you cannot install individual valves on them when it is done. You mention a "supply and return mains", but a MonoFlow system only has ONE main, and it loops from the boiler around the building and back to the boiler. You may have less of a problem than you think you do, but it would take a person familiar with heating to see where the problem is.

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