Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

2 pipe steam system main vent spitting water

I have posted these two pictures because I am baffled. This is an existing two pipe system. There are traps on the radiators but only these check valves on the return. The vent to the right is on the end of the supply pipe. The one on the left which is spitting water is the return pipe. I have the system set for less than 2 psi. 
A question I have is since I cannot put the vent back in the return piping where it should be. Could I put 2 90’s out of the riser where the vent is and move the vent away from the riser and will this stop this nuisance?


  • KC_Jones
    KC_Jones Member Posts: 5,241
    Those vents have a float to stop that from happening, so I speculate they are broken.

    There shouldn't be water there in that quantity to come out, so the real question is:

    Why is it there and how do you stop it?

    I'm going with a pressure issue, or clogged return piping, but I'm sure other will be along with some ideas.

    2 pipe should be running at ounces of pressure, what is the system running at?
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Jamie Hall
    Jamie Hall Member Posts: 19,895
    The first villain I'd look at would be that check valve -- clogged or just not opening on the small pressures required. It shouldn't be needed at all, but if you are running too high a pressure -- over a pound, and should be no more than half that -- some misguided soul may have though that having it would prevent water from backing out of the boiler and flooding the returns. Which, of course, doesn't work.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • I replaced the Honeywell 

    PA404A1033/U pressure switch

    With a Honeywell L404F1367 and turned it to the lowest setting with a .5 differential  
    it’s on a Weil McLain 88 series boiler 
    the gauge hi limit psi switch and operating switch 
    are piped out the front of the boiler to a 90 facing down to a tee. This is at the water line. I don’t know why Weil McLain has this as there recommended piping as water does get into the controls. The gauge at the time of water spewing was reading 1-1/2 lbs
  • Jamie Hall
    Jamie Hall Member Posts: 19,895
    You should be using a vapourstat as the primary control on that system, set at 7 ounces cutout with a 4 ounce (subtractive) differential. You can keep the PA404A as a safety backup.

    There are a lot of ways to pipe your pigtail(s) on a Weil-McClain so that water doesn't get into the controls.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Vinnie Smedick_3
    JUGHNE Member Posts: 10,018
    I had the vents spitting water on a 2 pipe.
    The issue was water not returning properly, a long story of improper install.

    You can take the top off that swing check and perhaps remove the guts, put the cover back on the empty body and see if that improves things.

    I am guessing that with the height of the return pipes, you do not need the check valve if running low pressure.
    Vinnie Smedick_3