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Radiator Air Vent(s) Gurgling & Spitting

Well…I’m back with a different problem in a different house and hope you guys can help.

This is a 1928 2 fam. Brick, attached house. The two original (one for each apartment) coal fired furnaces were replaced with one, oil fired American Standard furnace in the 1950’s. And the original burner was replaced with a Beckett about 7 years ago. Things have always worked fine.

This year it seems I have a new problem and I don’t know why. Two of the cast iron radiators on the second floor spit water from the air valve and they gurgle. This seems to be more pronounced in the morning when recovering from night time setback. It’s not a lot of water, but enough to wet the floor (and annoy the tenant).

Here’s what I’ve checked so far:

1. Pressure – the furnace cuts out at 1-1/2 lbs. and back in at ½. I even changed the 0-3 lb gauge with a spare to make sure.

2. Radiator pitch – one of the radiators was pitched slightly toward the valve and I increased the pitch a bit - so that is not the problem. The other radiator is a different kind – see photo (It’s not a photo of the problem radiator, but just want you to know what type it is because I don’t know the name).

3. Air Vents - I’ve tried several different make & model air vents. The ones with the smaller holes don’t hiss as much, but still spit in the morning.

The only things different this year are:

1. Last year I had some work done to get that apartment ready for a new tenant. It included removing and replacing the radiators (but not the one in the photo) in order to sand and refinish the hardwood floors.

2. As part of me annual burner service last spring, the technician replaced the nozzle on the burner. He said that he put in a smaller one, but maybe not. See photo of the firebox – is that flame too big?

I’d appreciate any thoughts you have on where I should look/check next to find out where/how the water is getting and staying up there.


  • BobC
    BobC Member Posts: 5,473
    The type of radiator in your picture typically wants a small orifice on the air vent, make sure the work done didn't shift the piping. Try shimming both ends of the problem radiators so you lift the whole thing up - making sure to keep some slope so water can flow back to the boiler.

    Would not be surprised to find a 90 year old house settling and that could alter the slope of the steam pipes. Go over any horizontal pipes you can reach and make sure they all slope back towards the boiler.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Abracadabra
    Abracadabra Member Posts: 1,948
    1. Pics of near boiler piping.
    2. Has boiler been skimmed?
    3. What does water line do while steaming? How much does it bounce around?
  • FXProglJr
    FXProglJr Member Posts: 83
    Thanks much for your thoughts. I had run out of things.

    BobC.......the workers didn't do anything to disturb the piping other than disconnect and reconnect the radiators - I was there to watch/help. I realize that there must be water getting stuck somewhere, but didn't consider the problem of the house settling. I'll try lifting both ends if I can and let you know how I make out. And that radiator currently has a Gorton #6. While I'm at it, I'll also disconnect one of the radiators again to look into it and see if there's anything to see and check the valve to make sure the washer isn't stuck down on the seat (even though the stem is all the way up)

    Abracadabra......near boiler piping hasn't been altered...ever. And I haven't done anything to warrant skimming. I'll get some photos posted and try skimming after first trying the above. As for the water level when making steam - the sight glass level drops about 1/2 inch when the steam is up (but I suspect that's to be expected) and it does bounce a bit when making steam - maybe 1/2-3/4 inch - about the same as the other 2 similar houses on the block that I have access to.
  • MilanD
    MilanD Member Posts: 1,160
    My recent experience with steam speed/volume ratio: you said you replaced and decreased the burner orifice nozzle? He may have altered the BTU input down enough where he created increase in the steam speed (less btu on the same op pressure = more steam speed).

    Lower nozzle decreases the system BTU slightly and increases steam speed and now it can pick up some water in the rad (this is a convection one, so smaller inside space). Steam is now just fast enough to push that condensate up and out. You need to lower the op psi cutout, or get a bigger flame (more BTU) to the burner as it was before the service, to decrease steam speed.

    It's all counter-intuitive.
  • MilanD
    MilanD Member Posts: 1,160
    Oh, you also said you redid the floor. Did you sand under the rad too? This may have lowered it just so to require being raised and re-pitched, per Bob's comment.
  • FXProglJr
    FXProglJr Member Posts: 83
    yes, they sanded under the rad. Tomorrow's job (if I'm up to it) will be to disconnect one of the radiators again to look into it and see if there's anything to see and check the valve to make sure the washer isn't stuck down on the seat (even though the stem is all the way up) and then try to raise both ends of the rad to increase pitch on the feed pipe while maintaining the proper rad pitch
  • Abracadabra
    Abracadabra Member Posts: 1,948
    A #6 is probably too fast a radiator vent imho
  • Danny Scully
    Danny Scully Member Posts: 1,416
    I find recessed cast iron radiators should be left level. Because of their design, if you pitch the vent side you're actually backpitching the inlet side. The vent is also in the wrong location. It should be lowered half way down the radiator. This will allow the sections to heat hot from top to bottom.
  • FXProglJr
    FXProglJr Member Posts: 83
    OOPS....you're right....there is a Gorton #5 on there now and I'll have to try a #4
  • FXProglJr
    FXProglJr Member Posts: 83
    well...it seems the problem is solved......my thanks to all.

    I removed one of the rads and checked inside (nothing suspicious) and inside the valve (the washer was up with the stem and not stuck to the seat). At least now I know nothing wrong there. I also attached a pressure gauge to one of the rads - same reading as at the boiler - 1-1/2 lbs max.

    I was able to raise the feed end of the 1st problem radiator (40" long x 24" high free standing c.i. radiator) about 3/8", maintain the slope back to that end and replaced the air vent with a gorton #4. If I watch the vent when the steam is coming up, I can see it still lets a little steam out that condenses to a drop or two of water, but nothing like before. Think I'll leave it alone.

    The other radiator that had a problem was a 30" recessed c.i. radiator. I put a gorton #4 there also and it's ok now also.

    Now that's done, maybe someone can comment on these two thoughts:

    (1) the two radiators that had the problem of spitting water out the air vent are the only ones that have a Danfoss thermostatic valve on them. Could that contribute to the problem?, and

    (2) while this problem was going on, I sat upstairs one day and just watched the air vent (after a day or two several, both new and old vents of different manufacturers, had failed and the steam coming out scared the tenant). It seems that they didn't close when the steam got there (which explains all the water....well, not a lot, but enough to leave a small puddle on the floor or wet a paper towel left under the vent). One seemed plugged up and didn't open at all so the rad stayed cold. So my question is "Could there be something in the rads or the steam that could foul an air vent? Why only these two? And, if yes, what should I look for and how should I handle it?"
  • Fred
    Fred Member Posts: 8,542
    edited February 2017
    Depending on the type of vents you are using, Some have a drip tongue on them that, depending on the radiator, may actually push up against the inside wall of the radiator and not let the condensation drip out of the vent if they are screwed in too far. That water in the vent will prevent it from closing like it should. Take those vents off and shake the water out of them, then use a little teflon tape on the thread (do not tape past the end of the threads) and put them back on without over tightening.