My apartment's radiators are loud and letting out steam. Is that normal?

October 31, 2013 7:59 AM

We've just moved into a new place and it's now gotten cold enough to turn on the heat. Two of the radiators are really loud with air escaping, and often have visible steam coming out of the valve on the side. I've never seen radiators do this. Is this normal? Is this safe?
posted by msbrauer to Home & Garden (9 answers total)

Not "normal", but not uncommon. Either the steam pressure is turned up too high at the furnace or, more likely, the valves on the side of the radiator need to be replaced. They are supposed to let air out (assuming you have a one-pipe radiator system), but not steam. A very common failure is that those valves don't stop letting gas escape when steam reaches them.

It's probably not unsafe, but it's something you (or your landlord) should fix because it cuts down on the efficiency of the system.
posted by Betelgeuse at 8:04 AM on October 31, 2013

Yeah, you should probably just replace the valves on the noisy ones. They're not expensive and can be found at most hardware stores.

Google 'radiator valve replacement' for videos and more info.
posted by Short Attention Sp at 8:25 AM on October 31, 2013

The valve could just be open. If you have a valve key or can get one from any hardware store then you can turn them closed.
posted by The 10th Regiment of Foot at 8:29 AM on October 31, 2013

Betelgeuse is right - a correctly functioning air vent closes to keep the steam in the radiator. It may be clogged with a bit of crud from the system. Between heating cycles, close the valve that feeds the radiator, unscrew the vent and soak it in vinegar for a half hour or so. If that doesn't fix it, then replace the vent as soon as possible.

BTW - the valve feeding the radiator should always be completely open or completely closed, i.e., don't try to regulate the heat by throttling that valve. If overheating is a problem, check into thermostatic vents.

(I believe the valve key is for bleeding air from a hot water system.)
posted by she's not there at 10:01 AM on October 31, 2013

Some steam will come out the air valve because the radiator needs to fully fill with steam after being off all summer. However, if your radiator air valve is squirting water and steam and/or there is loud knocking, there's a good chance your steam radiators have pooled water in them. The radiator needs to be on a slight incline above the steam pipe so water that accumulates when the radiator cools drains away.

If it's just continuing steam, I agree with Betelgeuse- your air valve may be malfunctioning. Sometimes a stiff piece of wire inserted into the valve will knock the moving parts loose and allow it to function properly. They are also easy to replace.
posted by oneirodynia at 1:12 PM on October 31, 2013

Unless . . . have you determined if they are steam radiators (one pipe, coming in) or hot water radiators (two pipes: one coming in, another coming out).

The behavior you describe would be normal for steam radiators. Proponents of steam radiators love them for being a little more efficient than hot water, and for adding humidity to the air in dry winter months.
posted by MeiraV at 9:05 PM on October 31, 2013

1. Call building management to do anything with the radiators: imagine you unscrew the vent (bullet shaped, or tiny drum/squashed cylinder shaped?) and soak it in vinegar. Then the heat comes back on and it turns out the (main) valve is broken! Steam pours out the vent hole, or the valve suddenly won't open again or or or. Or you go to put the valve back in but the threads in the radiator are all rusty and then, oops! stripped.
None are headaches you need or want.
The valves are 'cheap' and 'easy' to replace, but there is the potential for tedious disaster there.

2. If the steam is not jetting out and burning anything, then yes it's annoying but not dangerous. Call management anyway because (as said) the valves should let air out (and in) but close for steam, and if they aren't it affects the whole system. Sometimes the vents will 'leak' little wisps of steam and then shut off after a while. This is pretty par for the course.

But (and I says this from experiences, years an years of it) though straight forward, messing with radiators is something you should leave to the plumbers.
posted by From Bklyn at 1:30 AM on November 1, 2013

Thanks for all the advice here.

Unless . . . have you determined if they are steam radiators (one pipe, coming in) or hot water radiators (two pipes: one coming in, another coming out).

I think this is why the behavior is so strange to me. I've only had hot water radiators before, and looking now see that these must be steam radiators. I still think one or two might have issues with the valve, but now realize why these are behaving so differently from radiators I've known in the past.
posted by msbrauer at 6:56 AM on November 1, 2013

You can put wooden shims (sold at hardware stores) under the legs furthest from the radiator valve, which is near the ground and connects the radiator to the main pipe (not the air valve a/k/a vent, which is on the side of the radiator). As someone mentioned up top, this tilts the radiator towards the pipe so water doesn't accumulate in the radiator and can flow back out.

Or you can replace the air valve. I agree don't do it yourself. Have the super do it. It could break off if it's old and then the problem is worse. Also the kind of valve you need to get depends on how far the radiator is from the boiler. The further away it is the larger the valve opening needs to be. It's not as straight forward as it sounds.
posted by lillian.elmtree at 6:49 AM on November 3, 2013