Leaking radiator, house edition
September 9, 2022 10:03 AM   Subscribe

The heat's been off for months, why are the radiators leaking?

Details, and thanks in advance:

- Old, multi-storey house with steam heat.
- Crown boiler, installed in 2013 and in need of cleaning (hard water in house, sludge at bottom of sight glass), is in the basement.
- Boiler was shut off in April for the season.
- Leaking radiators are on the first floor: #1 is a bathroom baseboard with fins, #2 is freestanding cast-iron and in the dining room.
- Leaks are by the air valves.

Bonus: Leaks started on Monday, and maintenance appointments never showed. Recommendations for companies in Queens, NY, are also much appreciated.
posted by Iris Gambol to Home & Garden (9 answers total)
 
I think it’s condensation.

Pressure relief valves often seal effectively only when they’re under pressure, and can leak a little bit when nothing's pushing against them.

I’d feel more confident about this answer if the temperature had gone down a little just before they started leaking, because that would cause water vapor in the heaters to condense on the inner walls and then run down to leak out of the valves.
posted by jamjam at 10:45 AM on September 9, 2022


Your valves might be designed to exhaust air trapped in the system when it’s first turned on, and in that case they might be open by default under no pressure.
posted by jamjam at 10:51 AM on September 9, 2022


Response by poster: Thanks, jamjam. No temperature dips over Labor Day weekend, and more than a liter of water so far from the cast-iron radiator.
posted by Iris Gambol at 11:46 AM on September 9, 2022


Best answer: A liter is way too much for condensation.

I hesitate to suggest this, but is there any way your boiler could be filling with water? A leaky intake valve or a boiler water level sensor that failed?
posted by jamjam at 12:11 PM on September 9, 2022 [3 favorites]


I think jamjam has it. Many steam boilers have an autofeed valve which keeps the boiler topped up with water as needed. If it has failed, it will slowly (or quickly) fill the entire system with water. There's only supposed to be steam and a tiny bit of condensate liquid in pipes and radiators of the system when it's running. They should be more or less dry when the system is off. You can probably close the feedwater valve and drain the excess water out of the boiler if that's something you're comfortable with. (Also, be sure the boiler does not fire while the autofeed is off...low water level can destroy it.) This won't fix anything, but it will buy you time to get it repaired.

Heatinghelp.com has a message board called "The Wall" and a list of knowledgable steam contractors. Might be worth asking for advice on there or finding a contractor using their list.
posted by Larry David Syndrome at 12:46 PM on September 9, 2022 [4 favorites]


Seconding heatinghelp.com as a good reference (though take Holohan's historical research with a grain of salt!)

If your boiler is well and truly off, this means your boiler and a lot of your pipes are indeed full of water, since there's no way for the water to make it all the way up to the ground floor unless there's more water all the way beneath it. I agree with jamjam that a leaky (or not completely shut) intake valve is a likely culprit here. One thing you can do pretty easily on your own is empty the boiler (for which there should be a tap right at the bottom to which you can attach a garden hose). If you see more than a five-gallon-bucketful of water, that raises the likelihood of a leaky intake valve. And then you can do the same again the next day, and if there's any water at all, you've got your answer. (Make sure to turn off your auto-filler first if you have one!) If your tank is sludgy this is a good thing to do anyway; I blow down my boiler weekly during the heating season on the advice from my maintenance guy.

I have used Vigilante Plumbing for steam pipe maintenance and they have done a fine job. They're not cheap, but they show up punctually, they're easy to book, and their fixes are comprehensive and correct (as you probably know, the boiler-maintenance companies handle everything up to and including the flame and the plumbers handle everything wet, so this is a plumbing issue).
posted by goingonit at 1:04 PM on September 9, 2022 [4 favorites]


(also: the air valves should be all the way open until the temperature in the radiator hits boiling. A leak during heating operation is likely a valve problem but a cold leak can't be the valves.)
posted by goingonit at 1:05 PM on September 9, 2022 [1 favorite]


Yep, I had this problem(a very slow leak in the auto fill leading to filling up a good bit of the system with water). We solved it by adding a proper ball valve above everything in the system and turning that off each spring.
posted by rockindata at 3:57 PM on September 9, 2022 [1 favorite]


Response by poster: The culprit was a faulty sensor. Thanks everyone!
posted by Iris Gambol at 4:28 PM on October 17, 2022


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