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Concerned about Main Vents in basement

njhouse11 Member Posts: 8
edited January 2018 in Strictly Steam
So my house was built in the 1930s and has a one pipe steam radiator system powered by a new gas boiler. Radiators all appear to be cast iron / steel convectors recessed into the walls and there are 13 radiators throughout the house.

While there does seem to be excessive hissing the main problem is that the radiator in our bedroom makes a lot of noise ( some banging, lots of tings, sounds like waves of steam) and heats up last as it is the furthest from the boiler and on the top floor.

We recently bought the home last summer and it looks like the previous owner(s) haven't done much to maintain the system over the years. We have replaced several vents on individual radiators which has helped a bit but from reading this forum and others it sounds like my main vents my also need some work.

Here are the two mains that are in my basement one for the front, and the other for the backside of the house.

Front - https://imgur.com/a/ap3Qr

Back - https://imgur.com/a/S386E

Closeup of Back ( Looks to be Gorton #1) - https://imgur.com/a/BIlV4

When the system is running the main vents don't appear to vent much air at all while the vents on many of the radiators hiss a lot and I am concerned the main vents might be just old and clogged. Any advice would be appreciated.

To add, the pressure is set at .5 and the sight glass is about half full of water


  • BobC
    BobC Member Posts: 5,478
    The steam mains should be vented fast and the radiators slowly, you can't over vent a steam main but you can over vent a radiator.

    The mains should be vented proportionately so a 40ft main would need twice the venting of a 20ft main. Make a list of the radiators on each main that lists the radiators EDR, the length and size of pipe that connects it to the main. Looking at that list will enable you to take a good first stab at what vent to use where.

    While you doing the measuring check the slopes on the mains, radiator runout pipes, and the radiators themselves to be sure they have consistent pitch back towards the boiler.

    For main vents 3ea Gorton #1's = 1ea Gorton #2 and two Gorton #2's = 1ea Barnes and Jones bigmouth.

    Convectors usually want to be vented slowly and radiators want to vented proportionately to the amount of air the radiator and it's piping contain.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • njhouse11
    njhouse11 Member Posts: 8
    Thanks Bob, I will try and take a look at that. I know one of the radiators on the second floor has a Gorton #1 attached to it through some connecting pipe that attaches to the 1/8 inch opening that the vent would normally be connected directly to. Seems like that might be over-vented.
  • acl10
    acl10 Member Posts: 349
    What happens if you overvent a radiator?
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
    acl10 said:

    What happens if you overvent a radiator?

    Depends on how much overvented. If it's just too fast a radiator vent, not much -- except that it will steal steam from any other radiators on the same riser. If it's significantly overvented, the steam may be able to move fast enough to zip across the top and get to the vent and close it before the radiator has a chance to get full.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England