water is coming out of air vent in radiator

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    • #275983
      MasterPlumbers
      Keymaster

      I have water coming out of a first floor radiator thats located appx. three feet from a gravity return line in a one-pipe steam system. The return line is connected almost to the end of a steam main with an air vent appx. 34 ft. distant from a 2 header boiler. The other header services a steam main with no air vent that also goes into a smaller length return line which goes appx. 15 ft. to the back of the house. Both return lines come together in the boiler room that connects to a Hartford Loop pipe to the boiler. The radiator and steam pipes are pitched correctly. My question is: Why is the water in the longer length return line being pushed up into the steam main in the front of the house? Could the pressure from the boiler together with the other return line be causing this? If so, what can be done about this? Thanks in advance for your responses.

    • #293226
      Harold Kestenholz
      Participant

      One pound steam pressure will push water down 14 inches and up the other side of a loop 14 inches, so keeping the pressure in the system low enough (Systems are designed at 1 psig) to prevent water rising higher than the distance from the boiler water level to the main is important.

      The proper way to pipe the returns is to drop them both below the water line and up to the Hartford loop inlet tee at the equalizer pipes to the boiler. This gives a water seal for boiler supply main steam to be separated from the return. Vents eighteen inches from the drop elbow to the seal trap can then expel air from the one-pipe main in the right direction toward the Hartford inlet. You might have the pressure too high, no water trap drop, and no vent near the end of the longer run; check to see the cause in the first piping diagram at: http://www.oldhouseweb.com/stories/Detailed/10464.shtml

    • #293227
      jakemt
      Participant

      Harold, thanx for replying to my query. I would like to elaborate a little further on my water problem. The return lines are piped together below the waterline in the back of the boiler on the floor of the basement. A Hartford Loop pipe then arches vertically appx. 8″ upwards to a horizontal pipe which then is attached to the equalizer pipe appx. 1 to 2″ below the boiler water level. So I don’t think the problem is there. However, when the boiler is running appx. 20 mins., I notice the water in the sight glass fluctuating with the pressure gauge needle moving rapidly between 1 and 2 psig. That’s when the steam at one of the furthest radiator pushes water out the air vent. There is a fuctional main air vent at the point where the return line connects to the long steam main. This steam main then branches into 2 smaller steam mains going in opposite directions. Is the placment of this main vent correct? Also, what would cause the water in the sight glass to fluctuate? Is this causing the steam to partially push return line water back into the smaller steam main? Or, is this return line clogged so condensate cannot fully run down the return line back to the boiler? Thanx again for your input.

    • #293228
      Harold Kestenholz
      Participant

      Long reply done by direct email concerning locating main vents near ends of main branches, bad piping arrangement.

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