Why is my radiator so loud?

February 11, 2009 10:14 AM

Why do the steam radiators in my apartment make such loud banging noises? Is there anything I personally can do, or do I need to pester my landlord?
posted by ztdavis to Home & Garden (9 answers total)

That would be water hammer. The system might need a flush.
posted by backseatpilot at 10:43 AM on February 11, 2009

Make sure all the radiators are propped up at the end away from the pipe, so they have a slope of about 1/8" per foot to 1/4" per foot.

And yeah, occasionally the system needs to be drained and have fresh water put in.
posted by notsnot at 11:15 AM on February 11, 2009

Pester the landlord to repair or replace the air chambers or water hammer arrestors which will fix the problem, and emphasise that this will prevent costly repairs. The water pressure may also be too high, but if it is a large building that might require more than just reducing the pressure. The water hammering is very hard on pipe joints and over time will certainly lead to plumbing failure or pipe rupture. Arrestors eventually break and air chambers need to occasionally be cycled (refilled with air) so these are likely the problem, especially in an older building.

You should ensure that your radiators are proplerly draining by raising one end to allow the steam/water out. Note: not all radiators have a return, those will only have one pipe coming in and should have a valve at one end that may need replacing. If you are handy you can make your own air chamber for minimum investment, and they are relatively inexpensive to aquire if the landlord doesn't see the benefit of keeping water in the pipes.
posted by zenon at 11:16 AM on February 11, 2009 [1 favorite]

These are steam pipes, and not filled with water. There should be no need for any waterhammer chambers.

The banging could be related to expansion and contraction. Pipes get hung up in walls and ceilings expanding or contracting until they slip free, and WHAM!
posted by Gungho at 11:37 AM on February 11, 2009

Wikipedia says it is not exactly water hammer, and it isn't the pipes moving either (at least not in my case). The radiator in my office makes huge explosion noises regularly but the pipes have not moved or banged against the wall in the 5 years that I've sat here. That article explains it as "condensate that is unable to drain," and I always had it explained similarly as pockets of steam "exploding" when the condensate changed back into to steam in the hot pipe.

As for a fix? This Apartment Therapy link may have some good info. I'm guessing you may try to get your landlord to take a look at this before trying anything DIY. That thing is HOT!!
posted by sararah at 11:55 AM on February 11, 2009 [1 favorite]

The banging in our radiators was caused by water. The radiators weren't tilted in the right direction, so some of the condensation got trapped. We solved this by propping up the 'free' end of each radiator, to let the water drain back to the boiler. If you have someone to do this with you, it's pretty easy. You can buy round or square cups (intended for use under legs of heavy furniture) at a hardware store, or you can use wood shims or furring strips...or improvise. In our place we needed 1/2" to 3/4". Cardboard isn't good because it compresses over time.

Here is a clear explanation. My radiators didn't need to be disconnected, but if yours do, a pipe wrench is cheap and easy to use.
posted by wryly at 12:07 PM on February 11, 2009 [1 favorite]

It is possible that the pipes are moving around and making the noise, but you'd likely see movement. Steam making noise is not tecnically water hammer, it's pipe chatter, and the boiler is tecnically a water heater, and the arrests and valves that eliminate pipe chatter are not necissarily water hammer arrestors (although some actually are). Semantics aside, when the OP talkes to the landlord, the landlord should know that they aren't using water hammer in the strictest definition, and will understand the nature of the problem. Much more details here where the author outlines 17 reasons steam radiators make noise
posted by zenon at 12:33 PM on February 11, 2009 [1 favorite]

Propping up one end of the radiator (oposite the pipe connection) helped some for me. Ultimately, the landlord claimed it was due to a drop in the quality of city-supplied steam, with more water in it. They installed some kind of trap at the input and it helped.
posted by StickyCarpet at 2:22 PM on February 11, 2009

Best answer: wryly and sararah have it. In a working steam installation, steam leaves the boiler, condenses in the radiator, and trickles back down to the boiler at the bottom of the pipes (pretty neat trick for ancient technology, by the way). In order for the water to clear the pipes they all need to be angled back to the boiler, as does the radiator itself. There are actually specs for this which you could get from your local plumber's union (and probably City Hall, too) if you really wanted to.

If liquid water is in the pipes when hot steam comes up from the boiler, the steam insta-boils the water (usually not much of it), and the rapid boiling causes the loud pops you hear echoing through the system. For diagnosis: pipes expanding from the heat sounds like gentle haunted house creaking; stuck condensate sounds like Beezelbub banging pots and pans together all over your house staggered with rifle fire.

So the solution is to make sure everything's tilted correctly. The radiator needs to be higher on the side opposite the feed pipe than at the feed pipe, and all the "horizontal" (eg, not vertical) feed pipes should be at an angle also. You have to be careful not to over-do it, of course, since black iron can crack (especially at T & L joints), but you ought to be returning it to its original very-slight grade.

Usually the problem starts because the original shims under the radiator rot out or are removed, which levels out the radiator and also lowers the feed pipe. If the feed pipe leaves the radiator and then goes down through the floor, lowering the radiator inlet lowers that next joint and can level (or tip the wrong way) the next horizontal stretch of iron.

In our house I didn't realize until too late that replacing the floors also lowered them by about an inch. We had horrible banging until I figured out what had happened, and I had to put the radiator on 1" shims to get the right angle on the feed pipe (it's either that or re-plumb the steam system; no thanks).
posted by range at 3:24 PM on February 11, 2009 [4 favorites]