Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Indirect hot water heater with gas steam boiler?

I am converting to gas heat and hot water from oil.  I am getting different opinions on whether it is advisable to have an indirect hot water heater with a steam boiler.  Some plumbers say that while it will work initially, within 2-5 years the heating coils will become clogged with rust and debris and will fail.  Others say no, that a filter can be placed and that the indirect system should work fine.  Does anyone have experience with this and can comment?


  • Wethead7
    Wethead7 Member Posts: 170
    Steam & hot water

    I would not use a coil installed in the side of the boiler(oil or gas). I would use a indirect with a non wet rotar pump. You may find lower first cost using a stand alone water heater. Tank type or tankless would be less costly , most likely than an indirect. The indirect should least costly to operate. The tankless installed in the boiler most likely lowest installed cost, but comes with the highest operating cost. The stand alone tank type next up on installed cost, then tankless stand alone. Indirect most likely top end of the installed cost.

    Your installer should be able to help you with your choices. You may have other issues like space, flue, fuel source and others that could limit your options.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    non wet rotor pump

    I am curious why you recommend a non wet-rotor pump. My boiler and indirect hot water heater manufacturer recommended a  Taco 007 circulator for the smaller size boilers and indirect tanks, and 0010, 0011, 0012, 0013, and 0014 for larger boilers and indirect tanks. All these are wet-rotor type circulators. They basically want from 6.4 gph to 22 gph depending on the sizes.
  • Montykitty
    Montykitty Member Posts: 3
    Correction to question

    Sorry, I wasn't clear.  The plumbers were saying that the coils within the indirect water heater become clogged - not anything in the boiler.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    The reason for non wet rotor pumps

    The ferrous oxides from the cast iron system (essentially an open system) will lock a wet rotor pumped up tighter than a drum. There is not enough filtration available to get it out of the water.


    There was an error rendering this rich post.

  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666

    I infer your reply applied only to steam boilers. I know next to nothing about them.
  • jp_2
    jp_2 Member Posts: 1,935
    can't you

    force a steam boiler only to make hot water in the summer?   seems this would be possible?   would save money if you can run the steamer at 170F during summer for making DHW.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,322
    Yes jp

    The boiler runs with an aquastat for the indirect when the system does not call for steam to heat. On some systems I wire the aquastat to turn on the boiler only when the indirect calls for heating fluid. This makes it a cold fire instead of keeping the steam boiler hot all day just incase the system needs to heat the indirect.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
This discussion has been closed.