Quieting a Noisy Steam Radiator

Category: Do it Yourself

So we have this steam heating furnance.

The Problem
Each time the radiator was going on, it sounded like pistol shots in the radiators. Very loud, very SUDDEN noises. You could hear water sloshing in the bottom of the radiators. And then the steam valve on the side of the radiators began to spit rusty water on the wall, floor and anything nearby.

Our Solution
Head to the internet, to find out more information about Steam Heat. Use a combination of boiler maintenance and home remedies to adjust each radiator so that it drained properly.

(Image courtesy of: Old House Web)

Read on for how it went...

Diagnosing the problem...

We have a one-pipe steam heating system...the pipes are original. The furnace is approximately 7 years old. After reading some information about furnace ongoing maintenance, we found out that noise in a steam furnace is called "pounding" (sounds like too quiet a word from our experiences) and may happen when "...steam sent out by the furnace meets water trapped in the system. If this pounding happens in the radiators themselves, this could indicate condensate (condesation of steam=water that is colder than the steam), thus blocking the pipes."

We decided to try two things..."shimming the radiators" and performing a task of routine maintenance the previous owner showed to us that we hadn't done in the last 4 weeks or so. Shimming consisted of sawing down thin layers of board to fit under the feet of the radiator furthest from the pipe that carries water back into the system. We shimmed five of our loudest culprits.

The routine maintenance was emptying some water out of the furnace from a special valve until it ran clear. Not a pretty job, because the initial water out is thick with rust. I don't know why--because I'm told that it is normal--but rusty water makes me UNhappy. I pulled out the bucket normally devoted to this task (the one coated with rust stains) and got to work pulling two buckets out.

Down the drain in the basement floor it went .

I checked the pressure gauge and the water level gauge.

The water level gauge is thick with rusty water deposits so it is difficult to tell where the water level is. It should be halfway full. The pressure gauge was the big surprise. Instead of being above (what we read was) the "required" 5 to 7 psi, it was below...too far below? I don't know what "too far below" is. It was registering "0". This wasn't mentioned in our research and doesn't feel right.

How it Went

The knocking in the radiators was DEFINITELY less tonight. No cannons going off. No rusty water spitting out of the steam valve. No sloshing. But there was still noise NEAR the furnace. I hadn't investigated any noises near the furnace last night, I was preoccupied with the radiators. The noise near the furnace was so loud and violent, one good "pound" dislodged a piece of plaster from the ceiling.

I backed away very quickly.

This has to have happened before from the looks of the ceiling.

I am definitely pleased with the work at radiator level. Not so pleased with some furnace elements. We should have that visual water gauge cleaned and the pressure valve checked. We should have pipes from the furnace to the first floor checked for "rise". The pipes are supposed to rise at an angle that measures 1" from start to stop. (The house settling over the years has taken away from this necessary "rise"...I'm betting on it.)

Tools & Materials We Used

- Internet website, Old House Web
- Bucket
- Saw
- Piece of wood cut into 5 pieces
- A's brute strength to lift one end of 5 radiators
- Drain in basement

Yup, sounds like the cannons are in our basement now. At least they are no longer in the bedroom. Hmmm....

Looking for More?

House in Progress Search for more on 'steam_heat' on this site.
Houseblogs.net Search for 'steam_heat' on on other houseblogs like this one.
Google Search for 'steam_heat' on Google.
Amazon.com Search for 'steam_heat' on Amazon.com.


Go to www.heatinghelp.com for a lot more useful FAQ's (there is an excelent book for $20) that will have your system running smooth in no time.

We too have one-pipe steam. The sources you've found so far are good -- there's a wealth of information at http://www.boilerroom.com/homeforum.html -- and some really helpful people too. The alternative name for "pounding" that I learned there was "water hammer" which seems to me a MUCH more descriptive and appropriate term.

Good luck and thanks for the site,


Make sure all exposed steam pipes have adequate insulation, e.g., in the basement. People often remove the original asbestos insulation because of safety concerns. However, without it or a proper modern substitute, the system will never work properly.

I ran across your posting when I was searching web to find out the proper radiator angle to optimize the heat output . Our 1939 colonial has a similar system to yours. You can drain the boiler and then remove the glass water level tube for cleaning. When we replaced our original steam boiler the plumber recommended two things to add to the new boiler. A low water shutoff and an automatic water feeder if the water level is too low. This system works great. One other thing - I was also concerned about the rust - the plumber put an additive into the boiler water that controls the rust. It lasts for about a year if you don't drain the water. I did it the first year and then I just got used to the rust.

I had a new steam boiler installed and thought I would use a lot less gas this winter it seems as thjough I am using just as much with the old system.

I have radiators do the air valves on the side of the radiators need to be replaced?

Could the radiators just be bad?



Normal operating pressure for home steam systems is 1.5 to 2 pounds, not 5-7. And yes, that does not register on the gauge that comes with a modern boiler. 10 pounds or so will destroy the air values on the radiators. And generating extra pressure drives up the bills without heating the house.

Air values need to let air out (the rate gets adjusted to balance all the radiators in the house so they heat together), close on steam, and open again on a slight pressure drop (so the pressure setting on the furnace control is very important and has to match the air values on the radiators).

The Lost Art Of Steam Heating is a wonderful book and explains a lot.


Thanks for putting that comment here, I actually learned that nugget of info later (and talk about it in a recent blog entry). I was looking at the psi for water radiators, I think? Something else for sure.

Steam pressure should actually be between 10-12 pounds if you have 2 sories. Since you have no pump, the pressure of the steam needs to be higher to force it up. Your loud pounding in the boiler sounds like you might have a flame/air mixture problem. Also, try bleeding the air out of your radiators, it greatly increases the btu out-put. 10 pounds will not destroy your valves. They are designed to run up to 15 pounds of pressure

Hi Sean--Thanks for dropping by the site.

Although some boilers are made to operate at 10-12 psi, our specific boiler model and make operates most effectively between .5-1.5 psi

You can get more information about the different types of psi readings for steam boilers by searching the archives at Boiler Room Forum


Did you look through all those keys to find the "bleeder" key for bleeding the radiators?

That is what my grandpa (DuPont Plumbing & Heating) called letting the air out of the radiators each fall.

I have an unusually problem is their help?. I have a three family house and a lot of water is coming out of the air values on the radiators. This is a steam system and pressure is set correctly and the water gauge pressure is at the right height. The radiators are giving off heat, already pitch, and were bleeded but water is still coming out the air values. What to do ????

I have radiators through out my house. They work well and make no noises. My question is about maintainence. It has been a cold winter and I would hate to come in and find one of the rads has cracked or burst. Is this possible if they are left on all the time? Should I be doing some routine maintainence to avoid problems similar to this in the future?
I bleed the rads in the fall. Any other advice?

I have a one line steam system just like you explained. I was having the same hammering in the basement, I located the main line vent and found that it had been in place since 1936. Went to plumbing supply and bought a replacement. Did the trick... no more noise.

Hi - do you know a good, experienced plumber who can quiet down my radiators and check my steam system...the valves hiss load and the heat is eratic...I needs someone near Quincy, MA 02171..thanks, Peter

House was raped to an apt. complex now it's back to a single family dwelling does it matter the size and or the design of the radiator when the boiler starts it's loop?All of my radiators are the same except 1 looks victorian all the rest are same style other than some are larger than the others.When boiler starts it's loop the first radiator it comes to is a small one.By the time it gets to the last 1 which is about 3' long in our bed room were freezing.When I touch the pipe at the begining of the loop i leave skin on the pipe,but when I touch the pipe at the end it seems to have run out of steam.Any suggestions?


Anyone with steam or hot water boiler questions would be WAY better off turning to a site like Boiler Room or ordering the booklet at Heating Help We're really not qualified to give advice on home heating...trust us. You DON'T want us to give advice to you on this subject. We're just two old house owners telling their story.



Email this Entry to a Friend

Email this entry to:

Your email address:

Message (optional):

a neighborhood of home improvement blogs

Cabinet Refacing
Cabinet Refacing:
Face Your Kitchen | Your Guide to Kitchen Cabinet Refacing