Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

Steam heat help: What is this valve that's spitting water?

mayzejanemayzejane Member Posts: 19
Howdy all! I just bought a 1920s house that has steam heat. The boiler is newer but the radiators all have problems (they all spit water and hiss). However, my bigger problem is this pipe that is UNDERNEATH the bedroom radiator. It's spitting up water and causing a lot of mold and rot right beneath my master bedroom. Here's a picture of it:

Does anyone have any idea what this pipe is and why there is a weird protruding vent that spits water. Should I just replace that vent? From reading on here people seem to recommend Groton? But do I need a certain size for that long pipe and then a different one for the radiator above it?

Any help would be greatly appreciated! Thanks!


  • MilanDMilanD Member Posts: 1,114
    edited March 2017
    Looks like a lot of deferred maintenance on that vent if all that plaster damage has happened from that one vent... That vent looks like an attempt for a main vent. Angle of the photo is not showing where that vent is coming out of, but it looks like it's straight out of the main. This will push water and any other debris right in it, clogging the float and making it stick open and let water out under pressure.

    You need to do one thing first, and that's make sure your operating pressure is as low as it can be on your pressuretrol, and that the pigtail is not blocked/clogged. All your vents spitting water can very well mean your op pressure is way high. Near boiler pics of all the piping will let us see better, including close-up of the pressuretrol, glass water level gauge, and the pressure gauge when boiler is running. There may be easy fixes, or it may be more complex - getting the pics will help determine.

    For now, yes, changing the vent should help and also lowering of the op pressure. If you don't address pressire, I am only wondering if due to its location and the high op pressure and the overall system state that can be seen on the photo, that vent may start leaking again quite soon. Letting the water out on the vents and valves, that is - all that leaking and water loss, will also negatively affect the boiler longevity as it takes on a lot of new water. All the leaks need to be fixed.
  • mayzejanemayzejane Member Posts: 19
    Thanks so much! Here's a picture of the boiler, the pipe I had shown before is in the garage which runs the length of the house to the boiler. Do you think I can get any vent or should I get specific ones? I want to replace all the radiators (there are 5 total in the house, originally 7 but I removed 2) and then that weird vent in the original photo.

    Boiler pic:
  • Danny ScullyDanny Scully Member Posts: 1,221
    edited March 2017
    Step back from the boiler and take a few pictures. Where are you located?
  • mayzejanemayzejane Member Posts: 19
    That's Danny, will report back when I get home. I'm in NY.
  • Danny ScullyDanny Scully Member Posts: 1,221
    Where in New York? I operate Scully's Plumbing with my brother and father in the Nassau County area of Long Island if we can be of service.
  • LordoftheringLordofthering Member Posts: 8
    Bring down your water level to below half site glass level and run your boiler on manual water by turning off automatic water feeder. If you need water add manually. It is likely your auto feeder is overfeeding water. I had tow boiler at my rental which had 3/4 suggested level water still it was causing this issue of pipe hammering, leaking water, high pressure. Everything gone with simple solution after calling 6 different plumbers who could not fix issue.

    It is worth a try and will not cost you anything.

    Good luck
    Bob Gagnon plumbing and heating
  • KC_JonesKC_Jones Member Posts: 4,401
    Why do you want to replace all the radiators? And why did you take out 2? Removing the rads has the effect of oversizing the boiler for the system which negatively impacts system performance
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • mayzejanemayzejane Member Posts: 19
    @KC_Jones , I meant replace the vents in the remaining 5 radiators! I took out one in the bathroom because I put it radiant floor heating and then one was buried in a rotting wall that I had to take out.
  • MilanDMilanD Member Posts: 1,114
    edited March 2017
    Is the garage the farthest point from the boiler? Are there any other vents on the main pipe in the basement?

    In practice, you need to vent your mains as fast as possible. New vent on the market is called Big Mouth from Barnes and Jones. @Sailah can get that to you. Depending on number of mains or length, you may need more than one. Also, it needs to be in a right location, usually right after the last radiator riser.

    As far as radiator vents, look for Hoffman 1A, or a vent rite adjustable. I still have 20+ year old Hoffmans that are doing fine. These 2 vents will also make it easier to balance your system and make it heat evenly.

    I've not used vent rites but have Hoffman, and know Hoffman is well made. Others on the board have used the vent rite and say it's also fine.

    Finally, it's not a bad idea to get a good pro to look at your boiler and make sure it's operating at its optimum and to teach you how to properly operate your boiler. A lot you can learn here, but you also need to find a good steam pro for repairs and maintenance that's above the scope of a homeowner. If you are close to @Danny Scully, you'll be set.
  • mayzejanemayzejane Member Posts: 19
    @Danny Scully, @MilanD - Thanks so much guys (I'm in northern Westchester so probably out of your service zone!). I replaced one radiator valve so far and it looks like the water stopped spitting out of it (awesome!). Now I need to do the main vent and the others. I searched the entire pipe and I only found one main vent. Is that normal? It seems like there are two pipes going in different directions. One to do right side of the house and one to the left. Here's some more pics closer up to the boiler and following the pipe:

    Is that Gorton main vent at my local hardware store good enough for that? Or will I also need to change the pipe fitting?
  • MilanDMilanD Member Posts: 1,114
    I can't see from the angle of the picture how is that vent attached to the main. Looks like a 1/4 tap from a fitting. Can you get a close-up of that connection?

    This vent pipe size will determine max vent speed, and thus which vent to use. Let me find the venting capacity chart and I'll post back.

    Also, did you address the op pressure?
  • MilanDMilanD Member Posts: 1,114
    Looking at this chart, seems like even an 1/8 tapping is sufficient for an ok venting. This chart will give you vent rates for main vents and various radiator vents (see attached).

    I mentioned earlier Hoffman 1A and vent-rite for radiator vents, but there are others, of course. One good one I have used is also maid-o-mist. You can find that one on Amazon.

    I have used a maid-o-mist at the end of one long radiator riser to speed up the venting to it, in essence, using it as a sort of 'main' vent. Capacity of maid-o-mist is somewhat less than the expensive Hoffman 75, fwiw, but is better then no vent.

    Here's what I mean:

    All the best!
  • mayzejanemayzejane Member Posts: 19
    Thanks @MilanD ! You rock! Here's a close up pic and addressed the pressure!
  • AbracadabraAbracadabra Member Posts: 1,948
    mayzejane said:

    Thanks @MilanD ! You rock! Here's a close up pic and addressed the pressure!

    The way your vent is setup it'll trap water. Don't reduce on the horizontal.
  • mayzejanemayzejane Member Posts: 19
    @Abracadabra what do you mean by "don't reduce on the horizontal"? I was going to just buy what MilanD rec'd (the Big Mouth by Barnes) and replace just the vent. Do I need to replace something else as well?
  • FredFred Member Posts: 8,418
    edited March 2017
    That vent is mounted on a 3/4" elbow that is then reduced horizontally on a 1/8" pipe. Buy a 1/8" elbow and then buy a nipple and coupling that will let you expand to 3/4" vertically, under the new vent. It is currently holding water in that elbow.
  • MilanDMilanD Member Posts: 1,114
    edited March 2017
    I'd need to see also where and how this vent pipe is coming out of the main. So, a picture of the other side of that pipe - not the vent side but the other side.

    What @Abracadabra says, correctly, is that if you look at that 90 ell fitting, the bushing (reducing plug on the horizontal side makes the bottom of the 90 ell sit below the bushing and the straight pipe coming into it. This will hold water in the bottom of that 90 ell fitting as it's below where it can freely drain into the main. This water will just push out of the vent with rise in system op pressure, and as steam is hitting it it may first hammer (bad), and then squirt out (also bad).

    You want that 90 ell to be the same size as the horizontal pipe it connects to, then use a short nipple pipe and an 1/2 to 3/4 reducer with larger side pointing up (or whatever that straight pipe size happens to be)., or use a reducing 90 ell.

    Given you had water coming out of it in the past, I have a feeling it was a water plug in that very 90 ell that was pushed out of the vent like a geyser and kicked up the dirt into the vent, locking it in open position.

    So this after the same size 90 and a nipple use this:

    Or a reducing 90 ell:

    Or you may try street 90:

    Larger side, or the side that accepts the vent (Big Mouth and Hoffman 75 are 3/4) is facing the ceiling in all cases... Just get the proper size for the pipe that's on there now and to get it to 3/4. Street 90 will receive the reducing coupling directly for most space savings.
  • MilanDMilanD Member Posts: 1,114
    edited March 2017
    Also, one good project for spring/summer, after the heating season is done, is to slowly sand down the pipes, get all the loose rust off. There are various ways of doing this, from elbow grease and sand paper, to - faster - a wire wheel... Tools > Grinders + Accessories&utm_campaign=jmk-iit&utm_content=28365&gclid=CKai_oDu3tICFUkvgQod7V8NeQ

    Then paint the pipes with any good latex paint - semi or gloss. It will slow down the corrosion, and make it look nicer.

    BTW, do not touch anything that looks like asbestos, including asbestos insulation. Leave that alone. You can wrap it in some other insulation if you want to, or just plain old plastic, to keep it contained.

Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!