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Possible to modify steam radiator valve to add riser vent?

Is it possible to modify a one pipe steam radiator shut off valve to add a riser vent at the top of the valve? I'd rather not deal with the hassle and risk of drilling into the riser pipe to add a riser vent. I'm picturing some method of removing the valve stem mechanism and adding a riser vent at the top of the valve body. Possible? I've never disassembled a radiator valve so I'm not familiar with the internals.


  • Jamie Hall
    Jamie Hall Member Posts: 23,270
    Yesssss…. you could do it, provided you were reasonably handy with machining threads. The bonnet -- which holds the packing and the stem -- unscrews, of course, and you could machine a fitting which had the bonnet threads on one end and NPT threads for the vent on the other. You'd lose the valve function, of course.

    No mind you that I would recommend it...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Motorapido
    Motorapido Member Posts: 307
    Too bad I sold my metal lathe, mill and other metal shop tools a few years back. However, I could probably find an off the shelf fitting with threads matching the bonnet, and then an adapter fitting with the proper npt threads on the other end. But if the threads at the bonnet are not npt, how would I achieve a leak free connection at the bonnet threads?
  • acwagner
    acwagner Member Posts: 505
    The Lost Art has a figure showing something similar to what you want to do at the end of Chapter 8. However, they don't modify the valve. Instead, they replace it with an additional fitting for the vents and shift the radiator over.

    I don't think you'll be able to remove the valve stem without taking the valve apart, or at least disconnecting the radiator so you can access inside.

    Another alternative would be to tap the vent boss on the valve side of the radiator and put in a fast acting vent to act as a riser vent. Then put a really slow vent on the other side of the radiator.
    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

  • gfrbrookline
    gfrbrookline Member Posts: 753
    It would be much easier to add a Gorton D to the valve side of the radiator.
  • Mike Cascio
    Mike Cascio Member Posts: 143
    Putting a fast vent on the valve end of the radiator is a good solution. I did this on a hard to heat radiator and it helped quite a bit.
  • Mike_Sheppard
    Mike_Sheppard Member Posts: 696
    edited December 2019
    What method do you guys generally use to do this? Drill and tap the pipe?

    I had an apartment building that was originally a coal system. Only vents were on the radiators. One pipe system. 7 story building. Nothing ever came of it but I had suggested adding main venting and riser venting based on their complaints of extreme balance issues.

    I was looking into doing a 1/4 inch drill/tap at the top of each riser between the radiator and valve and adding pretty much whichever the fastest venting 1/4 inch vent is.

    Does that sound like I was on the right track? They decided not to go through with any of it so I never got into calculating how much air was in the mains / risers etc.
    Never stop learning.
  • gfrbrookline
    gfrbrookline Member Posts: 753
    You can do it two ways, @Steamhead tapped the riser in the unit below the last radiator and installed a Gorton D. The other solution is the tap the valve end of the last radiator in the run and install a Gorton D. 1/8 " tapping, make sure to tap with Npt.

    You still want to figure out your main venting before you do anything with the risers or radiators. I was going down your line of thought two years ago, added more main venting, slowed the radiator venting and everything balanced out. My rule of thumb is don't put anything on a residential radiator larger than a Gorton 5 and test that it closes. I prefer Vent-rite #1's to dial it in in unless you are a landlord.
    EBEBRATT-Ed Member Posts: 15,510
    If you have an angle radiator valve take it off and replace it with a tee. Come out of the branch of the tee with a new straight radiator valve between the tee and the radiator Put the new vent on the run of the new tee.