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Radiator Vents...Need a Big One

AdmiralYoda Member Posts: 618
edited October 2019 in Strictly Steam
I could use some help on a couple radiator vents. I have two radiators that are problems. One at the end of each main.

On one main I have one radiator upstairs that is about 20ft from the end of the main in the basement (and main vent) and is the smallest radiator in the house. Even with an adjustable vent all the way open, it takes forever to heat up. I want to increase the size of the radiator vent to help get all that air out of the 20ft of piping and to get it to heat up faster.

On the other main, I have a single large radiator on that main and the main is pretty long....it goes to an addition attached to the house. There is NO main vent. No place for a fitting either...so the radiator does all the work. It has an adjustable vent opened all the way up it still takes a while to warm up.

Sounds like I need two big radiator vents. Any advice? Thanks!

My mains are an unbalanced mess, yes, and that will be fixed by a pro when funds allow...but for now I want to make the best of what I've got.


  • ethicalpaul
    ethicalpaul Member Posts: 5,618
    Do you have the ability to put a large vent on the line entering the radiator? It will be like a mini main vent. It will allow the air to vent out of the long supply line. Then you can put a nice slow radiator vent on the radiator itself.
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
    Intplm.delta T
  • AdmiralYoda
    AdmiralYoda Member Posts: 618
    I don't have reasonably easy access to the line entering the radiator....but I had thought about drilling and tapping the radiator on the steam inlet side to put a main vent. There is an area on the radiator with a spot that looks like it would handle a radiator vent but it needs to be drilled and tapped first.
  • Jamie Hall
    Jamie Hall Member Posts: 22,949
    I can't really recommend trying to cure a main venting imbalance problem with a radiator vent. Sometimes you get lucky. Sometimes not so much.

    See what you can do about main venting first.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • AdmiralYoda
    AdmiralYoda Member Posts: 618
    Agreed. But the 2nd main is very long and doesn't have a spot for a main vent. I figure anything is better than nothing.
  • acwagner
    acwagner Member Posts: 505
    You could try drilling a hole in a fitting near the end of the main and tapping it. Varivalve radiator vents, when open all the way, vent very aggressively--I think it's close to a Gorton #2.
    Burnham IN5PVNI Boiler, Single Pipe with 290 EDR
    18 Ounce per Square Inch Gauge
    Time Delay Relay in Series with Thermostat
    Operating Pressure 0.3-0.5 Ounce per Square Inch

  • Steamhead
    Steamhead Member Posts: 16,736
    acwagner said:

    You could try drilling a hole in a fitting near the end of the main and tapping it. Varivalve radiator vents, when open all the way, vent very aggressively--I think it's close to a Gorton #2.

    More like a Gorton #1, since the pipe connection is only 1/8 inch.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • BobC
    BobC Member Posts: 5,473
    At what rate are you venting the other radiators on the main with 4 radiators? Slowing them down might speed that last radiator up.

    tapping the input side of the radiator is worth a try.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Deltat210
    Deltat210 Member Posts: 8
    Not to hijack, I have the same prob, no vents except for the radiator, so Ive been playing with the radiator vents, bought cheap and HD and theyre junk, will be getting some recommended vents. One of the radiators upstairs has a plugged opening on the opposite side of the valve, can you pipe a large vent to it or would that defeat some purpose..
  • retiredguy
    retiredguy Member Posts: 888
    This is for anybody that has an old steam system with no main line vents. I wrote this for someone else that was having a steam delivery similar to yours. "One thing to remember, when these steam systems were installed, the choice of heat was usually coal. It came on in the fall and shut off in the spring. Between that time the system was always active. there was little need for main line vents. Today, we want the heating unit to be automatic and controlled by some type of thermostat so we could get rid of the "shovel". These systems were not designed to be cycled on and off so we had to adapt them for this type operation. Lastly, compared to the old steam/coal boilers, the newer replacement boilers are much smaller, contain very little water and have almost no steam chest which is a receipt for problems".