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Air Vent #1 - Malfunctioning?

AGPR2022 Member Posts: 1
I have a one pipe steam system that seems to keep losing water slowly and knocking in pipe at beginning of cycle.  I noticed the main steam vent on what I believe is the return main is emitting ALOT of steam not air which leads me to believe the valve is no longer working. Can anybody provide any advice? See pics below:


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    Considering the apparent size of your boiler, I would say you need more main venting; however that may not be the only cause of your problem.
    If your pressure is above 3 psi, that may account for the vent malfunction, especially if the boiler is oversized for the system.
    I would do a radiator survey, to determine its total EDR, and compare that to the square feet of steam on the boiler label. In addition, check the pigtail under the pressuretrol to see if it is plugged, allowing the pressure to rise out of control.—NBC