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Cleaning water boiler system before installing condensing gas boiler

bob eck
bob eck Member Posts: 930
Water boiler system installed new in 1957. The boiler is now fired with oil owner wants to install a condensing gas boiler. What product can be added to the water in the boiler and system to help flush and clean out the system before installing the condensing gas boiler? What is the best way to clean out the old system? With the old boiler still installed or flushing the system after taking the old boiler out? This is a building with eight apartments and all are on one zone.


  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    If the new boiler has aluminum heat exchanger, ...

    ... do not flush the system with trisodium phosphate (TSP) as you cannot get it all out and your heat exchanger will not like it. Weil-Mclain recommend you get in touch with Rhomar Water Management, Inc. You may wish to look here:

  • Ironman
    Ironman Member Posts: 7,339
    edited May 2012
    Flushing System


    I would recommend removing the old boiler and flushing the system before the new one is installed.

    I would first flush with plain water until it runs clear on each loop. Then, if needed, use chemicals as needed and recommended by their manufacturer.

    A lot of debris/rust, etc. can be removed with white vinegar and a pump cart. A very cheap but effective method.

    If the piping is too complex to flush each loop separately, then there are chemicals that can be temporarily left to circulate in the system, but I would still try to flush as much out as possible with the boiler disconnected. Also, install a strainer or dirt separator as close to the boiler in the return line as possible.

    As JDB pointed out, Rhomar has some good products.

    Fernox is another very good product. Boyertown Supply is carrying it. Fernox also makes a filter with rare earth magnets that is great for collecting rust and iron debris.

    Mark Eatherton also has a method of using a chemical feeder with magnets placed in it that he's posted here previously.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Thanks Bob, but...

    That was Brad White who'd done that before, on his own system as I remember. I use magnetic water conditioners, but have yet to deploy them in a closed loop, although Caleffi just made it real easy to do with their new dirt separator...

    My friend, the Heatmesiter has a new water treatment system that he moves from system to system, and he has magnets in it, and he said you'd be AMAZED at what he's getting out of these non O2 barrier systems.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • gennady
    gennady Member Posts: 839
    edited May 2012
    system cleaning

    for initial cleaning sentinel x400, for conditioning sentinel x100, disconnect old boiler first.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Gennady reminded me of something.

    In the W-M installation manual, they recommend Rhomar for boiler water treatment products.

    Soon after I got my Ultra 3 boiler, W-M came out with a recommendation to put Sentinel X-100 in it. They even supply it with each new boiler.

    I have no idea what is in either of the two products (the stuff you leave in), but each seems to have a similar product.

    They each also make a cleaning solution you put in, run for a while, and then remove.
  • Ironman
    Ironman Member Posts: 7,339
    Thanks for the correction Mark

    I knew it had to be one of you two very clever gentlemen and you were the one that came first to mind.

    Regarding the amount of rust produced by using non barrier pex: I've gone behind others who have done this and found the results extremely damaging.

    I just installed a Knight WHN in place of a Munchkin Contender that was 2 years old and was connected to 7500 feet of non barrier radiant floor piping. The heat exchanger was leaking like a sprinkler and the MBR was plugged with rust. All the piping is coated with about a 1/16 inch of rust. But the installer saved a few $$ by using non barrier pex! I isolated the new boiler from the system by using an indirect and will return next week to begin the clean-up of the piping.

    I'll post some pics after then.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
This discussion has been closed.