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DHW Issues

pqc Member Posts: 2
Question can a Therma-Flow coil (625-5, resident in a Weil McClean boiler) be back flushed? Although I know I am on borrowed time with the boiler, I would like to mitigate the lack of hot water pressure and consistent temp. The unit is 23 yo, but I cannot afford to change it out yet...and, besides the coil, the unit is in good shape. I swapped out the mixing valve, which increased water temp by about 20 dg...but coil is definitely blocked...and yes, we are on well water. The $600 or so that it would cost to have someone come out and change it doesn't make sense, if I swap boiler out in the spring...thoughts?


  • Jamie Hall
    Jamie Hall Member Posts: 17,060
    Try to see if you can rig up an arrangement to circulate a strong vinegar and water solution through the coil. Or, if you can't circulate it, at least get it in there to soak for a while. That won't help with the scale on the boiler side of the coil, but it may get rid of some of the scale on the DHW side. Can't hurt anything...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • GBart
    GBart Member Posts: 746
    Just go to an indirect SS water heater, hook it up to your current boiler, it will match any boiler, Weil McLain cast iron boilers can last a lifetime
  • pqc
    pqc Member Posts: 2
    Jamie Hall...thanks - sounds like a good idea...I was just thinking of running water [backwards] through it...the vinegar may aid in the cleaning...!
  • GBart
    GBart Member Posts: 746
    edited October 2018
    Has anyone ever tried this over the counter remedy?

    CLR Calcium, Lime & Rust Remover is a powerful formula that quickly and easily dissolves and removes tough calcium and lime deposits as well as surface rust stains from bathtubs, toilet bowls, sinks, glass, chrome, fiberglass, stainless steel, most coffee makers, humidifiers, dishwashers, washing machines and showerheads. The formula also is perfect for use on RVs and boats. CLR Calcium, Lime & Rust Remover is part of the EPA’s Safer Choice Program and contains no phosphates and is Septic Safe .

    I've used it for faucets, shower heads, shower walls floors, etc etc, but it never dawned on me to run it through a coil.....hmm, you can use it in coffee makers and dishwashers but not water heaters with tanks, it has to be completely flushed out.
  • hot_rod
    hot_rod Member Posts: 15,027
    I have use this high power acid, it is approved for DWH use, but pay attention to the directions. 2018-10-10 18.29.41.png?dl=0
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream