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What are these pipes?

mculik5 Member Posts: 30
I'm new to steam heat. I'm doing some work in my house, and made a simple 3D model to help me understand the system. It's a one pipe system. Please see attached picture.

The red pipes are the main supply pipes from the boiler. These are run along the ceiling of my basement. The yellow pipes are the riser pipes running to each of the radiators in my house (some on first floor, some on second floor).

What are the green pipes?

I thought steam and condensate use the same pipes in a one pipe system. So what purpose do the green pipes serve? Parts of the green pipes are below the water line of my boiler, so they are always full of water. Why not just eliminate them and have everything run through red/yellow pipes?



    ALIGA Member Posts: 194
    green pipes are returns

    in a one pipe system, there are two types:

    parallel and counter flow.

    i will let the experts answer the rest.
  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    Your system

    is set up as a parallel flow, one pipe system.  What this means is that the steam and the condensate flow in the same direction in the steam mains.  The green pipes collect the condensate at the ends of the steam mains and return it to the boiler.

    The steam mains should all be pitched away from the boiler, towards the green lines at the ends.

    In a counterflow system, the condensate flows back to the boiler, opposite to the steam.  This requires larger pipes.

    I trust that there are main vents at the ends of the steam lines?  If not, adding them will help you get more even heat, faster.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • BobC
    BobC Member Posts: 5,477
    The water has to get back somehow

    The return pipes are for bring water back to the boiler. Your steam main probably starts high above the boiler and slowly slopes down as it goes along, if so it needs some way to get the condensing steam back to the boiler and the green returns do that job. If my description is accurate it is a parallel flow system.

    If the mains started low above the boiler and increased in height as they went along you would have a counterflow system and the mains might have to be larger because the steam and condensate would be flowing in opposite directions.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • mculik5
    mculik5 Member Posts: 30

    Based on Aliga's comments, I figured I had a parallel flow system. Thanks for confirming. And yes, there are vents at the ends of the mains.
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