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Undersized piping, 1-pipe steam radiator

I have a stream radiator that was installed about a year ago that always gurgles and often spits water out the vent. Taking a closer look, all similarly sized radiators on this floor use 1.5" piping and valve, whereas this was reduced to 1.25" near the radiator.
Besides re-piping this and getting a radiator that has 1.5" inlet, does anyone have anything simpler to try first to improve this?
(Reposting here as I see I picked the wrong category first time and can't seem to change it!!)


  • ChrisJ
    ChrisJ Member Posts: 15,690
    I see nothing wrong with that.
    How many EDR is the radiator?

    I have a few 50-60sqft radiators piped with 1.25".

    The valve and pitch of the radiator and the horizontal section of pipe would be where I'd be looking.

    What vent(s) are on that radiator?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    EBEBRATT-Ed Member Posts: 15,527

    could be the angle of the picture but the radiator look like its pitched in the wrong direction. should be lower on the pipe end
  • Erin Holohan Haskell
    Erin Holohan Haskell Member, Moderator, Administrator Posts: 2,286
    @PeterVs I've merged both of your posts here.
  • jhewings
    jhewings Member Posts: 139
    As Ed said, the radiator should be lower on the pipe end. So you can check with a level. If it is sloping down from the pipe end (not what you want) you might want to carefully raise the other end and insert blocks so that it slopes towards the pipe end. Maybe use a 2x4 on the floor and have a helper put 1/2" blocks under the feet away from the pipe. The feet near the pipe end might end up off the floor so put smaller blocks there too.
  • jhewings
    jhewings Member Posts: 139
    I meant use a 2x4 on the floor to lift the radiator at the end away from the pipe
  • JohnNY
    JohnNY Member Posts: 3,230
    Looks like a 40 sq ft EDR radiator.
    Here's something interesting:

    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
  • PeterVs
    PeterVs Member Posts: 3
    The pitch on the pipe is shallower than the other radiators, about 7.5"/10' versus 10"/10'. I can see why they did that as there's no space to go steeper.
    I believe the EDR should be around 36.

    I double checked, the radiator is sloping towards the valve, In the past I've tried making this even steeper but didn't seem to make any difference...

    The vents on the radiator are varivalve (the same as almost all the rest of the house).

    If it's the slope, re-piping is problematic as there's no space, is there something else that may work?
    One thing I forgot to mention, this radiator is the very last to heat, which is one reason I was thinking the narrower piping may be slowing things down/causing terrible).
  • BobC
    BobC Member Posts: 5,478
    Heatimer VariValves can be to aggressive for steam because they vent so fast and are hard to control at the low end of their range. They don't have floats so they don't seal against water.

    In general you want to vent the mains very fast and the radiators slowly. Fast mains venting will let all the radiator feeders get steam at about the same time. By venting the radiators according to the radiator EDR and that of the feeder piping you should be able to get them all filling with steam at the same time.

    Make sure all mains have good big vents near the ends and then try small vents on the radiators, increase the vent rates of radiators that seem to be to slow to vent. Because you don't know what size vent you will need I'd buyb the Maid O mist 5L that comes with 5 assorted orifices so you can change the vent rate by replacing the screw in orifice.


    I've had them on my radiators for years and never had a problem with them.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • mattmia2
    mattmia2 Member Posts: 9,653
    Where is this radiator in relation to the boiler? Is the water line in the boiler stable when it is steaming or does it bounce around? Is the valve all the way open?
  • jumper
    jumper Member Posts: 2,256
    Good suggestions above. May fix issue.
    Long branches on one pipe can be less than ideal.
  • PeterVs
    PeterVs Member Posts: 3
    Thanks guys! @JohnNY table is very insightful that the setup isn't ideal, though thankfully the pitch itself is probably ok even though shallower than others in the system. To @jhewings point I think the radiator slope is ok in the case.
    I think I'll start with seeing if I can improve things with the venting to @BobC point, it's the easiest thing to try at this point!

    @mattmia2 the radiator is on the first floor, the main line is about 13' from the boiler and the branch is another 11' to the radiator. The boiler waterline is stable and the valve is open all the way.