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Steam mains connected at ends?

BrianF Member Posts: 17
Ran into this the other day and I’ve never seen it before. Just curious if there is some sort of reason for connecting the mains. There is one 3”x 82’ main and one 3” x 36’ main. The ends connect with approximately 10’ of 2” pipe. I can’t see if it’s original or not under the fiberglass insulation. Whoever did it piped it in did it so that it won’t hold water  

It runs pretty smoothly, no noises, no surging or anything. They do have major balancing issues, wet steam and clogged pigtails which I partially addressed for now. Just curious if there’s a reason to connect the two mains or if it’s some whacky thing someone added to try and balance the system. 


  • Jamie Hall
    Jamie Hall Member Posts: 22,972
    That connection is going to give you almost impossible to resolve balancing issues -- no matter where you try to put a main vent or vents. Wonder why they did that?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Steamhead
    Steamhead Member Posts: 16,736
    Is this a Broomell system? We've seen several Broomells that had connecting pipes. We generally remove them and install main vents in the tees.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    EBEBRATT-Ed Member Posts: 15,353
    I have seen that and it is usually impossible to get the mains to vent. If there connected the steam from the short main will get into the long main backwards and close the vent on the long main (if it has one) and trap air so all they air vents through the rads causing slow heating.

    I would rip the 2" crossover out and install the right size main vents BUT make sure the condensate can drain out of the mains.
  • Mad Dog_2
    Mad Dog_2 Member Posts: 6,768
    Fascinating.   Can you post pictures?  Not ALL Deadmen - knew what they were doing or were great craftsman, but 99% were and did.  I've seen that in some houses where the lead and oakum cast Iron is installed on obtuse angles and all crooked from day one - probably by a Jack Leg-Stumble bum who took the pipe from a construction site and he was a laborer or something- NO Plumber.  Mad 🐕 Dog
  • mattmia2
    mattmia2 Member Posts: 9,475
    It may have worked with coal where venting doesn't happen very often. Maybe a shortcut to get condensate somewhere?
  • BrianF
    BrianF Member Posts: 17
    edited January 2023

    If it was a Broomell system all evidence of it is gone. It’s a Victorian mansion chopped up into apartments. Who knows what has occurred over the years.  

    The call for was radiators leaking on a Saturday afternoon. Steam was blowing from vents and valve packings. Apparently the thermostat apartment leaves it at 78 and opens windows to regulate the temperature. Well they left the windows wide open on a 55 degree day, left overnight and it dropped to 20. That boiler ran probably a day straight. The pigtails on both pressure trolls were clogged which didn’t help.  

    Main venting is there and undersized. They had a Hoffman 41 convector vent on the short main and Hoffman 75 in the long main. I put a big mouth on the long one and two Gorton 1s and the 75 on the short one to get them some relief for now.  The mains actually heat someone evenly now, about 2:30 for the short one and 3:00 for the long one from making steam. Probably should just about double that venting but I was working with that was in the truck Saturday afternoon. Pulled the varivents in the thermostat aprtment and put in Gorton 4s. Then repacked the leaking valves and replaced the pigtails. Now they can keep the windows closed and have a 6 degree temp difference between apartments in the building.

    Trying to talk the owner into increasing the main venting further and taking the Gorton Cs off the third floor radiators and doing riser vents which I think will get the temps even closer and get rid of some of the spitting up there.  If that connection in the basement does more harm then good maybe pull that as well or just leave it alone if it isn’t hurting anything. That’s the only thing here throwing me for a little loop  

    I’ll take some pictures next time I’m there. I’m in that building constantly for one thing or another. 

  • Long Beach Ed
    Long Beach Ed Member Posts: 1,188
    edited January 2023
    Circuit Piping or a "loop" main was common in some early installations. It's covered in Alfred King's 1919 𝘗𝘳𝘢𝘤𝘵𝘪𝘤𝘢𝘭 𝘚𝘵𝘦𝘢𝘮 𝘢𝘯𝘥 𝘏𝘰𝘵 𝘞𝘢𝘵𝘦𝘳 𝘏𝘦𝘢𝘵𝘪𝘯𝘨 𝘢𝘯𝘥 𝘝𝘦𝘯𝘵𝘪𝘭𝘢𝘵𝘪𝘰𝘯. Watch your pipe pitch. Usually as built, the system fed through one end and drained back through the other with a continuous pitch back to the boiler.

    Today for intermittent cycling I would split it into separate mains with near-equal loads, properly pitched or dripped.