Why radiators overflowed?

Trying

I'm trying to figure out the reason for some puddles under the boiler and radiators so that I can work out if my mom's heating system is ok now or needs work. Can you help?
The system is oil-fueled one-pipe steam heat in a house from 1915. All the radiators are on the first floor and those along one side of the house all had puddles underneath them this morning - one had just a cup of water, another the water had spread several feet across the floor. There was also water under the boiler and a bit of water on top of the boiler in the basement. The vents on the leaking radiators were wet, although the inlet valve of one of the radiators was also damp. The water level glass on the boiler was completely full. The pressure gauge was at 10psi. I turned the boiler off, drained the water off the boiler until the water level appeared in the glass and the pressure dropped to 0psi. This involved draining off 20-30 gallons of water. The system has worked fine for years. The water in it hasn't been too rusty so yesterday morning was the first time I drained half a gallon off in maybe 3 months. I think I topped up very briefly, leaving the water in the glass a bit above half. There is no automatic feed (that I know of) - I top up the boiler using a manual valve. There was a lot of very noisy banging yesterday afternoon when the system ran after I'd done the maintenance drain/top-up, which I unfortunately was too busy to investigate. So the most obvious explanation to me seems to be that somehow 30 gallons of excess water got into the system and when it switched on, this spewed out of the radiators. In which case, now that I've drained the excess, it should all be fine. But when I checked the boiler this morning, the intake valve was closed, and if I added any water at all yesterday it must have been less than a gallon as I remember being it being very fast. So although an error by me seems the mostly likely cause, I don't understand how it happened, unless perhaps the inlet valve is getting loose and continued to let water in. I hope that is enough detail! So my question is: is there another explanation for the banging and puddles under the radiators and boilers? or anything I should be worried about?! Many thanks for any thoughts you have

BobC

You may not have shut the feed valve off tightly enough, when they get old they can be tough. Does the boiler have a coil in it to make domestic hot water? If it does the coil may be leaking city water into the boiler.

If it does not have that coil you might want to replace the feed valve washer or the valve itself.

Bob

Fred

As BobC says, it has to be one of those two issues. Either the valve was not fully closed or is leaking or, if there is a How water coil in the boiler, it may have sprung a leak.

Trying

Bob & Fred, thanks so much for so quickly replying and giving me some clarity. There is no hot water coil. And the water level has now gone back up out of the glass, so it looks like the feed valve is leaking quietly.
Thanks again

Fred

It should be fine once you repair/replace that valve and lower the water level back to normal. Hopefully non of the vents will be plugged as a result of some crud washing up into them. If they don't vent, take them off and wash them out/shake them out