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Steam boiler overfilled

jsnapoli Member Posts: 1
I was topping up my boiler via manual feed and accidentally forgot to stop topping up my boiler via manual feed (something like https://forum.heatinghelp.com/discussion/125274/aftermath-of-overfilled-boiler). I was alerted to an issue when water started splattering out of the bathroom radiator (30 minutes to an hour later). I ran to the basement and closed the water feed (left yellow handle in the linked photo: https://bit.ly/2JozNsc). The glass water gauge was completely full.

Steps I took: 1) Turned off the switch in the bottom left of my photo (was this a bad idea?). 2) Drained about a cup of oily water out of the red spigot to the right of the water level gauge. I decided this was probably the wrong thing to do. 3) Drained a ton of water out of the blue spigot at the bottom of the photo. The water was slightly rusty, but otherwise fairly clean. Like 20 gallons. I think I only filled the boiler with a trickle of water for ~half an hour, so it seems like this was overkill. 4) I finally stopped draining the boiler and turned the electrical switch back on.

What steps should I take next short of calling a professional? Did I not drain enough water? Too much? Thanks in advance for any advice.


  • Fred
    Fred Member Posts: 8,542
    Drain the water level down to where it is suppose to be in the gauge glass and fire the boiler up. If any of the radiator or main vents don't close, when the boiler runs, you probably washed some crud up into them. Take them off and wash them out. You likely did not do any damage to anything, other than your ego.
  • BobC
    BobC Member Posts: 5,479
    I did something similar a couple of decades back, I had the flu and had gone downstairs to check the boiler water level. It was low so I added some. When it got to the right level, I closed the valve and went back upstairs.

    About an hour later the tstat clicked on and a few minutes later the system began playing the anvil chorus. I went back downstairs and found the sight glass full, I guess i didn't shut that valve all the way.

    I stopped the flow before it came out of any vents upstairs but I still had to drain several buckets and I don't have a sink or floor drain in the cellar. I had to carry 5 gallon buckets of water up the cellar stairs and dump them in the kitchen sink. After I got the level where it sb in the gauge glass I fired it back up.

    I got a few bangs when steam started to flow but that was probably just water getting into spots it shouldn't be. That was a sign of pipes with little or no slope having water in them, I fixed that in the spring.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • dopey27177
    dopey27177 Member Posts: 887
    Not a problem as all you needed to do was drain the water to the proper ware level for the boiler to operate safely. usually about 1/1/2" above the bottom of the gauge glass.

    If you have an auto feeder to the boiler in a short time the water level will rise to the proper standing water level of the boiler which can be 1 to 3" higher.

    The extra water that shows up in the boiler is the condensate return from the spent steam used for heating. This extra water prevents a thing called condensate lag.

    Condensate lag is the situation that will cause the boiler to short cycle.