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.

Underground Steam Pipes

brandonf Member Posts: 205
Good evening folks.
Does anybody have any experience running steam pipes underground for short distances?
I'll be buying a house soon that has a 1000 square foot garage in the back.
It was originally heated with steam in the early 1900s.
The original system is gone.
I may not want to heat it some winters since there's nothing I need to keep from freezing so I was thinking to have the boiler in the basement of the house and run the steam pipes underground to the garage.

The basement floor is about 5 ft lower than the garage floor.
The garage is 35 feet away from the house. I know how people run water and Electric underground to buildings but I'm not sure how it works with steam.
The house currently has a steam heating system as well.
All ideas and thoughts are welcome.
Homeowner, Entrepreneur, Mechanic, Electrician,

"The toes you step on today are connected to the butt you'll have to kiss tomorrow". ---Vincent "Buddy" Cianci


  • Jamie Hall
    Jamie Hall Member Posts: 22,892
    Insulate insulate insulate. And then some more. Both the steam main and the return.

    I would pipe it as a two pipe system with both the steam main and the dry return pitched back to the house. The main will be counterflow, so you won't have to worry about a drip from it -- collect the condensate from the main back in the boiler room. I'd use a crossover trap at the end of the steam main into the dry return, rather than a vent at that location, and put the vent back in the boiler room on the dry return.

    If it were mine, I'd be very inclined to put both pipes (and whatever else needs to go out there!) into a "utility tunnel" rather than direct burial, but that's getting a little fancy -- but it would radically reduce the heat loss from the steam main.

    You won't really have to worry about draining things if you do it right -- the only thing that will hold water at all will be the bottom of the radiator and a little water in the trap (if any). You can start it up by just hitting it with the steam, although if it's really cold you may want to make provision for heating the radiator trap until the radiator warms up some (above freezing).

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 15,300
    I would pipe the main counterflow (low in the house -high in the garage). That way when you shut it down the garage in the winter the underground will be "Dry" no water in it.

    Size the main as a counterflow main and pitch it like a conterflow main. You going to have to run a return line as well. Pitch that lower end in the house as well.

    With only 5' of vertical your going to have to use a condensate pump on the return. It's doubtful you can get the condensate back to the boiler without one. So basically your going to have to pipe the garage as a 2 pipe steam system.

    Or pipe a hot water loop off the boiler with a heat exchanger and glycol the garage size. You gould use Pex underground

    Might be cheaper $$$$ for hot water than steam.

    Unless you figure out a way to not need a condensate pump but I doubt it
  • The Steam Whisperer
    The Steam Whisperer Member Posts: 1,214
    If the whole setup was piped as a counterflow one pipe system, you should be able to start the steam main just a little above the water line and pipe it up hill to the garage. However, you would need to push the frost line up around the chase to keep it from heaving. Insulating above and a few feet out from the chase should take care of the frost issue and reduce the heat loss.
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • brandonf
    brandonf Member Posts: 205
    I was thinking as deep as possible with the tunnel and coding the top of it with 2 inches of spray foam before covering it with topsoil.
    the original boiler was in the garage in its own boiler room but I would have to keep it running all winter long or at least keep the boiler room warm all winter long.
    Homeowner, Entrepreneur, Mechanic, Electrician,

    "The toes you step on today are connected to the butt you'll have to kiss tomorrow". ---Vincent "Buddy" Cianci
  • mattmia2
    mattmia2 Member Posts: 9,404
    You may have to keep it 12" below ground minimum. Michigan's code was pretty vague, it really only talked about water piping, but I took that as applying to hydronic piping as well and that was what the inspector wanted to see.
  • dopey27177
    dopey27177 Member Posts: 887
    Since you may not want to heat the garage a good way is to install a unit heater hung from the ceiling with a separate "T" stat
    to control the desired temp. say about 45 degrees.

    You can do this by using the hot water from the boiler to supply the heat needed for the unit heater.

    Although this method is used to supply hot water to a second floor radiator it can be adapted for your purposes.

    This method negates the need for an underground steam supply and return pipe.

    The piping for this system can be Type L copper with sweat joints.

    If you do this be sure to insulate all the piping in the garage area.

  • mattmia2
    mattmia2 Member Posts: 9,404
    I'd do that but I'd use a HX (or even a tankless coil) and fill the loop to the garage with glycol.
  • Kjmass1
    Kjmass1 Member Posts: 241
    Might be cheaper to throw a minisplit in there rather than dig for all that piping. And you’d get AC too.