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Steam Boiler Drain Clogged

ewalls29 Member Posts: 26
edited September 2020 in Gas Heating
Hello all,

I have a Slantfin steam gas furnace and nothing is coming out of my drain valve. I tried to poke inside with a wire hanger and did see some gonk on the end wire but no luck.

I'm thinking to remove the drain valve and start poking inside with the wire. I just want to confirm if this is the right approach. I have read when there's a lot of gunk in the tank water in the sight glass is muddy, but as you can see the water is clean (regardless, I still want to flush the tank). The other thing that concerns me is the water in the site glass is waaay above the recommended water line level. So i'm not turning this puppy on until I get that to correct levels and thank is flushed with clean water.

Thanks in advance for you help!



  • Jamie Hall
    Jamie Hall Member Posts: 17,132
    It would appear that this is a steam boiler, not a furnace at all (furnaces heat air for forced air systems). That being the case, yes, you should be able to get water out of that drain valve. It's also not that uncommon for them to become clogged, and you can remove it and make sure that it -- and the passages into the boiler -- are free. Do this with the boiler off... while you are at it, make sure that the water level in the sight glass moves also. It's not unheard of for those tappings to get clogged, too.

    And... if those locations are clogged, I wouldn't be at all surprised if the pigtail leading to the pressuretrol or vapourstat was also clogged -- and should be removed and cleaned to make sure it is open as well.

    All this can and does happen even if the boiler water is pretty clear (yours appears to be).

    When you are done, restore the water level to the correct elevation (your is high, but not high enough to cause problems running the boiler, by the way -- assuming that it is real). Then run the boiler and make sure that the pressuretrol shuts it off when it is supposed to, and that the low water cutoff shuts it off when it is supposed to, and then again restore the water level, run it to drive off the oxygen in the water, and you're good to go -- so far as water level is concerned.

    You do have the burners and fireside passages cleaned and adjusted regularly, don't you?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ewalls29
    ewalls29 Member Posts: 26
    I stand corrected!! thank you!

    I have not turned on the boiler yet, which is why I want to take this opportunity to address the clogged drain. I'll be keeping your suggestions in mind once I get to it. Thankfully my boiler has ran perfectly, if not better, than most years.

    Since buying my house (will be 3 years next month),I never had the burners or fireside passages cleaned/adjusted. As far for the adjustments, are there any signs that would indicate one is needed? Apart from properly bleeding the mains and getting the correct radiator air valves, my system has pretty much kept up with the coldest of coldest winters.

  • mattmia2
    mattmia2 Member Posts: 3,991
    i like using this style of valve for boiler drain applications:
  • ewalls29
    ewalls29 Member Posts: 26
    @mattmia2, i've een those around, think I'll go ahead and change it while it's out. I can see why those would be better.
    JUGHNE Member Posts: 8,972
    I have used house pressure to back flush plugged drain valves on boilers and water heaters.

    I hook up a garden hose to a source, could be washer supply etc.
    Then use a double female at the boiler, I use a washer supply hose for that fitting.

    Then with the supply on I open the plugged drain valve for a few seconds. This will usually back flush and clear the obstruction.

    Might take several tries.
    Don’t let the boiler water flow into your house plumbing.

    Then when drained, change to a better valve for complete flushing.
  • ewalls29
    ewalls29 Member Posts: 26
    edited September 2020
    This is what came out!! I can assure you this is not a photoshopped image lol. The water came out completely black. Ran the cold water return for a full bucket and water was only a tiny shade from being clear. Installed the Full Port Ball Valve and all good now.

    As always, thanks everyone for your comments and help. This is an amazing site!
  • ethicalpaul
    ethicalpaul Member Posts: 3,137
    Congratulations but I am wondering why that drain is so much higher than the bottom of the boiler, and what gunk must remain on the bottom.

    is there another lower port somewhere?
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
    JUGHNE Member Posts: 8,972
    Paul is right, if you got that out of the higher port then the water below is worse.
    There should be a drain on the very bottom of the boiler, usually is factory installed. And usually a cheap drain hose bib that will plug up more then the one you had above.