How do I stop this new noise with my radiators?

November 11, 2004 4:59 PM

Radiatorfilter: I've got steam radiators in my house. Recently, I took them all outside and repainted them, then put new inlet and exhaust valves on them. So far so good, but when I fired up the furnace, I got a godawful racket. I'm used to the occasional clank from years past (and I went to gradeschool in an old building, so clanking doesn't surprise me), but this clanking is persistent and hasn't stopped for 40 minutes. So: how to stop the clanking? (also: anyone know of a good online reference to how the system works, esp. the exhaust valves?)
posted by notsnot to Home & Garden (13 answers total)

Sounds like you need to bleed the radiators. There's a little valve on each that you need a key to turn (any hardware store can fix you up for about 50 cents).

Basically this removes air from the system

http://www.diydata.com/problem/central_heating/bleed.htm
posted by baltimore at 5:11 PM on November 11, 2004

Response by poster: Unfortunately, that's for hot water boilers (which my parents have). I have steam, which does not have a return line at all, just a little bullet-shaped outlet valve that vents to atmosphere.
posted by notsnot at 5:29 PM on November 11, 2004

I have no answer to your question. But as a fellow owner of a single return line residential steam unit, I can offer you this counsel: You've got to be rigorous in draining/flushing the water-supply valving, even in the summer, or it will silt and corrode and require replacing at the tune of $800. Guess how I know.

But you sound like a competent guy who stays on top of that sort of thing.

Also I did find this interesting article:"Downsizing Steam Systems, which, if you haven't already read, you may find interesting.
posted by mojohand at 5:48 PM on November 11, 2004

Whu? Your steam radiator vents live steam into the rooms? Or do you mean something else by "does not have a return line"?
posted by five fresh fish at 6:24 PM on November 11, 2004

The vent valve vents air, not steam, and then closes - the steam reaching it heats a part which expands and closes the valve. A little steam will make it out prior to closing but mostly just air gets vented so as to allow the steam to enter and heat the radiator. If these new vent valves are too fast it can cause noise as steam quickly fills the radiator condenses and then fights the incoming steam. In a one pipe system the steam enters the radiator, and the condensed steam leaves the radiator, through one common pipe with just so much capacity. If the inlet valve is not all the way open a similar problem can occur. Since you just replaced the vents and valves I would guess that either the vents are too fast, the valves are too small or the valves are not all the way open (they are not throttle valves but are rather designed for on/off service). There could be other problems, but these are worth a look.
posted by caddis at 7:14 PM on November 11, 2004

One more thought, after you painted and then reinstalled the radiators did they have the same pitch as before? They should be tilted slightly toward the pipe to allow condensate to drain out of rather than get trapped within the radiator. I think condensate trapped within the radiator can also cause some noise.
posted by caddis at 7:53 PM on November 11, 2004

[Quickly adds Caddis to his speed-dial]

FFF, the ways these things work is that the boiler sends steam thru a single pipe to the radiators. As the steam cools in the radiator, it condenses to water, which travels down the bottom-most portion of the same pipe . Thus all the pipes - and radiators, as Caddis notes - must be aligned so they drain back to the boiler. Any dips, the water collects, steam doesn't get thru, you're cold, and the pipe hammers.

As these systems are only found in old houses, which settle every which way, getting the system aligned so they drain correctly can be a task.

While steam heat was hot technology (sorry) in the early 20th C., and actually have some advantages, what with this and having to drain it weekly, you can see why hot water systems and later, forced air, were greeted with acclaim.
posted by mojohand at 8:29 PM on November 11, 2004

Response by poster: I think you've nailed it, caddis...I turned one (short) radiator around to re-arrange the room, and a couple other radiators used to sit on the awful tile that I removed to re-expose the hardwood floors. I ran out to Home Despot (sic) and got some funiture slides, and put them under the offenders. I'll see if that helps on the next cycle.

In other news, one of the radiators (which incidentally, fell on me when I was bringing it back into the house) has a small crack in it. Should I buy a new one (shudder) or get it repaired? How does one repair one of these cast-iron monsters?

Despite the noise, they can pry my radiators from my cold, dead fingers...forced-air heating sucks. Too dry, dusty, drafty...
posted by notsnot at 8:33 PM on November 11, 2004

It has been many years since I dealt with these on a heating system project, but I believe we were able to braze some cracked cast iron radiators. We had talented welders available otherwise we probably would have just replaced them. Even then, I think brazing an aging cast iron radiator is no easy task. Good luck.
posted by caddis at 8:20 AM on November 12, 2004

As a cheap "solution" how about j-b weld
posted by stuartmm at 8:31 AM on November 12, 2004

Regarding the crack, aren't most radiators really a set of identical segments lined up in a row, with specialized "bookend" segments? There's (at least one) long bolt that runs secures them all together from end to end.

If that is the case for you, I'd guess you could just remove the cracked piece, cut down the bolt (if the threading extended down long enough) and just bolt the whole thing back together just a little bit shorter. If you can't just subtract one out for some structural reason, you might be able to find a replacement segment at one of those architectural salvage places.

_{Although I'd defer to caddis' knowledge on this one, of course...}
posted by LairBob at 4:40 PM on November 12, 2004

For understanding how your house works, I strongly recommend the book "The Virgin Homeowner." There is a terrific chapter about heating systems, including steam.
posted by plinth at 5:41 PM on November 12, 2004

Response by poster: Unfortunately, the radiator that is cracked si the *one* radiator in the house that's got screw-in nipples, i.e. it's threaded together. After 70+ years, there's no way I can unthtread one segment. I'll try JB Weld.
posted by notsnot at 6:36 PM on November 12, 2004