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Air vents pour water

guesswork Member Posts: 1
edited February 2018 in Gas Heating
Hi, I have a steam system and two radiators in my house are pouring out lots of water from the air vents when the steam comes on. The furnace is in the basement. On the first floor the radiator spits out about a cup of water. The second floor and furthest radiator spits out about 3-6 cups of water. This happens every cycle until boiler is out of water. I’ve replaced both air vents with new ones. Any thoughts?

note, 1st floor radiator has a pitch fixed by the in-wall casing which all looks good. this radiator makes a lot of clicking and bubbling sounds.

second floor radiator is old cast iron that was level until i pitched it with a block of wood on the side under the vent, opposite the return.


  • Jamie Hall
    Jamie Hall Member Posts: 18,958
    Several thoughts. First, does this happen at the beginning of a cycle, or near the end? And if near the end, at what pressure does your boiler cut out.

    Clearly, though, somewhere in the piping to those two radiators the water can't drain properly. First check that the valve to the radiator is fully open. Then follow back and check the pitch of every near horizontal pipe all the way back to the boiler. They must be pitched to drain somewhere. Usually bad pitch will give a water hammer, but not always.

    Also -- those vents are probably shot by now.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Fred
    Fred Member Posts: 8,518
    Pictures would help but I am guessing one of two things: either the supply pipes to those two radiators is too small to let the steam in and the water out or the system pressure is running so high that the pressure prevents the water from getting out of those radiators while the boiler is running. What is the Pressuretrol on the boiler set at? It should be set to .5PSI on the Cut-in scale on the front of the gray box and the white wheel, inside that box should be set to "1" for a cut-out pressure of 1.5PSI. Make sure the pigtail (looped pipe that the Pressuretrol is mounted on is not clogged with gunk. Is it is, the Pressuretrol can't see the system pressure to manage it.
    Is this a new/recent problem or has it always run this way? Also, as Jamie said, make sure the supply valve is fully open and that any horizontal pipes have a pitch back to the boiler. Are either of these radiators sitting on an area of the floor that has sagged? If so, you may have to raise both ends of the radiator to get the pitch back in the horizontal pipe under the floor boards and then re-pitch the radiator.