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Boiler running too long

bboogert Member Posts: 3
What would cause a one-pipe steam boiler to keep running long after all the radiator vents have closed? This is a recent change in behavior. I can hear the sound of boiling water echoing through the cast iron and lots of dripping inside the whole system. Clogged pigtail?


    JUGHNE Member Posts: 10,561
    Pigtail is a good start.
  • Fred
    Fred Member Posts: 8,541
    more likely thermostat but pigtail can let pressure build well beyond desirable, if thermostat is working and hasn't been satisfied.
  • Jamie Hall
    Jamie Hall Member Posts: 21,092
    Need to know what pressure is being reached. Because... a third possibility is that you have a steam leak.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • SteamingatMohawk
    SteamingatMohawk Member Posts: 840
    If your pigtail comes out horizontally on the side of the boiler, by all means, thoroughly clean it. With the loop going down from the horizontal connection just makes the probability of clogging worse. It seems many modern boilers are set up that way. My boiler has the Pressuretrol and gauge connected to the upper gauge glass connection. The two attachments, if readable, show the difference in arrangement.


  • SteamingatMohawk
    SteamingatMohawk Member Posts: 840
    When you click on the link, the image may be too large, just reduce the size and you can see the arrangement.
  • bboogert
    bboogert Member Posts: 3
    Thank you for these suggestions. I will investigate, but quick question about the pigtail...is there a special silicone tape for steam connections, or dope, or anything I should use when putting it back together?
    EBEBRATT-Ed Member Posts: 13,423

    Any pipe dope or teflon tape will do. Try not to get anything inside the pigtail
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,826
    I always use PTFE tape between brass and cast iron because it's a good dielectric.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • bboogert
    bboogert Member Posts: 3
    edited April 2020
    Thank yo7 all for your suggestions. Sadly, this project will go on hold until the plague passes. The system may not be running optimally right now, but it’s working and I don’t want to put anybody at risk to come fix something that I $&# up. I’ll get back to you when it’s safe aga8n.