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Spitting steam vents

I have a one pipe steam system that just started spitting water out of the air vents, I have done everything that I can think of and all of my industry peers can think of. Ihave installed main vents, checked all of the returns. Blew everything out checked radiator pitch, flushed and skimmed the boiler. The steam main starts to flood after approx 30 min of run.and it creates a vacuum at the rads when the system shuts down.

Comments

  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    Blocked Return Lines?

    if your steam mains are flooding, the returns might be plugged with gunk so the water can't get back to the boiler. Have them replaced.

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  • Blocked Returns

    I have checked all of the returns and they all return at the beginning of the cycle and at the end of the cycle. But something is preventing the system from returning when it get up and going. Kinda like the thumb over the straw .
  • Paul_11
    Paul_11 Member Posts: 210
    has anything changed lately

    You say this only just started to happen, but something has clearly changed.

    How long have you lived here?
    Has any work of any kind been done in your home recently?
    Could this problem have develped slowly without you noticing it?

    If the condensate water backs up and spits out of your mains, then we know for sure that the condensate water is stacking up too high in your return lines.

    We need to figure out why this is happening and why all of a sudden is it happening.

    Is something causing the residual steam from getting all the way to end of the main and helping the condensate return to the boiler. The addition of a zone valve could do this, an F&T trap would do this, badly designed repiping would do this.

    You say the water does return to the boiler when the boiler shuts down, but could the return lines be partially clogged? This would increase the friction in these pipes and possibly this increase could be enough to cause the condensate water to stack up too high and spit out of your main vents. This would mean you don't have enough A dimension anymore. If it is only a partial clog, the water would still return to the boiler when the boiler shuts off.

    Just some thoughts

    Respectfully,

    Paul B. Shay
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