All my steam radiators suddenly filled with water

Gordon_Of_EMass

Today I noticed that ALL of my steam radiators were suddenly leaking water out of the air vents, apparently because the radiators were at least partly full of water.  A few gallons leaked out of one.  I saw that the water level was out of sight above the top of the sight glass on the boiler, so I opened the drain.  At first a lot of pressurized air came out, and then 10 or 15 gallons, until I could see the water level in the glass. I should  mention that in the past couple of weeks, there was LOUD hammering in the pipes occasionally, as if someone was hitting the pipe hard with a hammer.



A similar thing happened a couple of years ago - no leaking that time, but the water level was above the top of the sight glass.  I drained out a couple of gallons until I could see the water level in the glass, and everything was fine (until now).



Whenever I add water to the boiler, I don't fill it excessively high - I can always see the level in the middle of the glass.  So I'm wondering, how does the water get "stuck" in the pipes and radiators? Is it because a bubble of steam forms in the pipes that blocks the water from draining back to the boiler?  How can I prevent it from happening again?



Thanks,

Gordon

MTC

Don't think that could happen...

due to radiators filling from steam trapping water. when boiler cycled off, it would drain, then flood the boiler. As the mains filled up, I don't think you'd get enough steam through all the water to keep filling the system.



Do you have an automatic feeder? If so, it may be failing and overfilling. If not, your manual fill valve might be leaking... badly it sounds like in your case.

Hap_Hazzard

Do you have an automatic water feeder?

Or is it possible that you could have failed to turn the supply valve all the way off the last time you added water?



Condensate can sometimes be slow to return to the boiler, causing the water level to drop during the heating cycle and return to normal after the end of the cycle, but we're talking maybe a gallon and a few minutes, not ten gallons and several days.

Charlie from wmass

leaking fill valve

is this an auto fill or auto fill system? If manual fill are you sure the valve is shutting off. If auto fill is the waterline unstable? Do you have a tankless coil water heater?

Gordon_Of_EMass

I have a manual fill valve

I haven't noticed it leaking before.  Maybe I didn't quite shut it off last time.  But would that account for water suddenly leaking out of the radiators on the first and second floor, way up above the boiler?

Charlie from wmass

yes

it would

Gordon_Of_EMass

The water level usually drops an inch or two

in the sighting tube a couple of hours after I turn on the heater.  Sometimes it drops enough that the boiler stops, and I have to add more water.  That happened last night.    So I guess either I left the feed valve open a bit, or it's an extreme case of condensate returning slowly to the boiler.



BTW it's a Carlin G3B burner, which replaced my oil burner.

Hap_Hazzard

I knew I was forgetting something.

Charlie, you're right on the ball, as usual. I knew there was something else that could cause boiler flooding, but I couldn't remember what it was. The old leaky tankless coil!

ToddB

Leaking fill valve

I had a leaking fill valve two years ago. I did not have as drastic a water level rise as the OP, but the water level would rise slightly over time after performing a weekly drain and refill to the cold water line.