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Steam heater holding 5 gallons of water, then dumping it all of a sudden!


We have had problems with our gas heated steam radiator system since we moved in 7 years ago. Every year it seems to need servicing. The boiler is probably about 10 years old. But the pipes and radiators are much older.

We have a little leak in a 3 inch pipe that a plumber has been attending to with a bucket under it. Not that big a deal. About a few cups of water a day. So every once in a while we had to add water to the system after the indicator light came on. Didn't seem too odd, since we had that little leak.

So last night I heard some banging like someone trying to kick in the door. It woke me up. I went downstairs and heard the "water hammer" of the steam trying to get past the water in the pipe. But it was not in the radiator, it was in the wall, in a vertical pipe. Suddenly, I hear rushing water, like someone is taking a shower. I head down the basement, and the boiler is over filled past the "normal" level in the water level glass indicator. I immediately started draining the system. There were 5 extra gallons of water! How is this possible? Where could the water be going, and getting stuck? And what should I do?


Dave T


  • 5 gal extra

    is there an auto feed on this system?

    do you have an exact reading of your system pressure in fractions of a pound [normal should not exceed 1.5 psi]?

    can you find a steam technician who doesn't "attend to a leak with a bucket"?

    i suspect that your system pressure may be so high as to force the water up into the dry returns where it can play badly with the steam. this is no doubt due to deferred maintenance [failed pressuretrol, clogged pigtail, etc.]

    some pictures of your system would help us narrow down the causes: boiler/piping, and radiators/valves,--nbc
  • David_T
    David_T Member Posts: 4
    no auto feed


    There is no auto feed on the system.


    The pressure is set to only 1 psi. And the shut off works. It cycles properly when it reaches 1 psi.

    The plumber is coming today to fix the leaking pipe this morning, but this leaking pipe is not the real issue for sure.

    When I get home I will snap some photos.

    Thanks for your help so far!

  • Mark N
    Mark N Member Posts: 1,090

    You may think a small leak is no problem, but it is. All the water that leaks out will need to be replaced. The fresh feed water brings wit it dissolved oxygen. That oxygen will cause rot holes to form right at the water line causing the boiler to fail. It is a lot cheaper to fix the leak instead of replacing a boiler. Is it possible the hand valve that you use to feed the boiler is leaking. Quite a bit of water can be in the pipes if the pitch of the pipes is off.
  • David_T
    David_T Member Posts: 4
    fresh feed has 2 levers


    The fresh water feed has two shut offs, so it's not leaking. You have to turn both on to get more water into the system. Oh, and get this. On Dec 26, the red light came on indicating I needed to add more water. And I thought, I just added water yesterday, maybe the water needs to trickle back down from the radiators. So I waited 3 hours. The Light was still on. So I added just enough to get the light to go off. Later that evening when when the pipes started banging, and all the water rushed back into the system. (see first post in this thread).


    David Taylor
  • mystery excess water

    is this a 1-pipe or 2-pipe system? if 1-pipe, then the radiator shut-off valves should be wide open, and never be closed as they can still leak steam, but hold the water. later on this radiator full of water can bang, and when the valve is opened, the water rushes back into the boiler, over-filling it.

    if the main vents are inadequate, then they can hold a vacuum which will hold water up in the returns until the boiler fires again, and equalizes the pressure, also dumping this now excess water.

    unless you have an accurate gauge, you can never know whether the pressuretrol is doing it's job properly.

    i agree with mark that any leak should never be tolerated. does this boiler make hot water also?--nbc
  • David_T
    David_T Member Posts: 4
    edited December 2011
    1 pipe system


    it is a one pipe system. I think the valves are bad. What you are saying makes sense to me. The water is getting into the radiator but not OUT. It has to be the valves.

    The plumber is here now replacing them and fixing the leak in the 3 inch pipe too. Fingers crossed.

    Thanks again for your input.

    David Taylor
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