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I hear a whoosing sound coming from one radiator at the same time every night - I have hot water heat


Dear Carmella:

I'm assuming that the sound that you are hearing coming from your radiator is happening when your heat comes on in the evening when the temperature starts to go down outside, and the demand for heat in your house goes up.

I suspect that the whooshing sound that you are hearing from one of your radiators is likely do to air trapped in this radiator that needs to be bled out. If this is the case, you will also notice that when its operating that the radiator will be warm on the bottom but cooler on the top.

To bleed your radiator, you will need a "bleed key" and a towel or bowl. Here is the procedure for how to bleed a radiator:

1) Turn off you hot water system (turning down the thermostat is fine)

2) Locate the bleed valve on your radiator. It will be located near the top of your radiator, typically towards the end.

3) Put your towel or bowel under the front of the bleed valve (to catch any water that drips out), and then insert the bleed key into the bleed valve and turn it counterclockwise. Don’t turn it too much; a half a turn is usually enough to allow air to start coming out. BE CAREFUL, because if water starts to come out, it may be scalding hot.

4) As you turn the radiator key, the valve will open and you will hear a hissing sound. This is completely normal and is simply caused by the air escaping. Once water begins to leak out of the radiator, then close the valve. To do so, turn the bleed key clockwise until tight.

5) Turn your central heating system back on.

You might find it helpful to watch this short video about how to bleed a radiator:

If this doesn't solve your problem, just let us know and we can try something else.

Hope this is helpful.


I've just moved home and my central heating seems to working fine except two of the radiators (one upstairs one downstairs) start rattling, making a noise like a pneumatic drill. To stop this I have to adjust the heat either up or down a bit. This works for a while but then it will start up again. I am forever rolling out of bed in the middle of the night to adjust the temperature. Help?


Dear Charlie:

I assume that you heating system is a steam radiator system, rather than a hot water baseboard radiator system, right?

If so, have you checked to ensure that all of your return lines slope towards the boiler?

If the slopes are fine, then the other source of noise could be that the expansion relief valves for each of these radiators have calcium deposits built up in them. To check this you would need to shut off your heating system, close the shutoff valve to the radiator, and then remove the expansion relief valve. Then soak the valve overnight in vinegar to loosen up the calcium deposits. Rinse and replace it back in, and turn on your heating system and open up the steam to this radiator.

If the radiator still rattles/bangs, but not as badly, then you could have hard water calcium deposit buildup in the radiator itself, which could be causing air in pockets to form. You can try to clean inside the radiator with vinegar or hard water calcium deposit remover, but depending on how bad the build-up is, you may be better replacing the radiator.

But before doing this, you might want to have a service technician come out to inspect your system, who can physically hear the sound that your radiators are making and inspect your system.

Hope this is helpful.


I have an electric boiler , hot water radiators in a two story semidetached home. When I turn up the thermostat there often is a terrible racket - it sounds as if someone is using a pneumatic drill. Sometimes this noise goes on for quite some time, other times the noise stops after a while. There are times when the noise doesn't start at all. How can I get rid of the racket? What can be causing it? Two plumbers have been in to fix the problem without success. Help would be appreciated!


Dear Rose:

Without hearing the noise and watching your system to see exactly what is happening, its very difficult to accurately diagnose what could be causing the noise you are hearing form your hot water radiator system. Since you have already had a couple of plumbers looking at your system, I assume that they would have caught all of the potentially obvious problems.

But here are a couple of thoughts about what else could be causing the noise that you describe:

1) your radiators or pipes that return water from your radiators back to your boiler are not pitched properly (i.e., that they do not have the correct slope to allow water to flow back to the boiler). As such, the steam is meeting the condensed water and exploding back into steam, which could be the cause of your noise. To fix this, a plumber would need to check and adjust the slopes of your radiators and pipes.

2) another possible cause is that one of your pipes goes through a tight spot in your wall somewhere, and when the pipe heats up and expands, it chatters as it tries to expand through the hole that is too tight.

Again, it is very hard to diagnose a noise problem like this without actually seeing your system.

Hope this is helpful.


Thank you for your speedy reply. The system worked well for many years, without any problems. The problem cropped up recently. I suspect the plumbers were not familiar with an electric boiler system.



Glad to be of help.

If your system has worked well for years, then the problem is likely not due to the pipe going through a tight spot somewhere inside your walls (unless you have moved walls, etc.). But over time, your radiators or piping may have shifted, and this could cause them to lose their proper pitch.

If this does not turn out to be the problem, just let us know, and we'll try to come up with another idea for you.


QUESTION FROM Concenrned Tami

Hi my landlord switched my boiler from oil to gas, well ever since I started my heat my pipes and radiators are banging I did real a little about it. I dont know how to get the air out. BUT IS THIS DANGEROUS as I have 3 kids.


Dear "Concerned Tami":

From what you've described, I suspect that the banging that you are hearing from your pipes and radiators is due to air that is trapped in the system that needs to be bled out.

You can read about how to bleed your radiators on the "Radiators" page of our online Maintenance Library:

And also, if it would help you to see a video demonstration on how to bleed air out of a radiator, you can see short video here:

Assuming that it is just air trapped in your system, this is annoying and reduces the efficiency of your heating system, but it is not necessarily dangerous.

Home this is helpful.



We have 3 radiators upstairs (one of which is a towel dryer in bathroom) and 2 radiators upstairs. I have bled all the radiators as we are now looking to use the heating regularly. Last time i used the system about a month ago, all was well but now when the heating is turned on there is a relatively high pitched pulsating sound that you can hear anywhere in the house...after about 45 minutes of the heating being on this sound stops.

The system has been on for about an hour now and I can hear the gentle flow of water in the upstairs radiator in my bedroom, I cannot hear a similar sound from the other radiator in my back bedroom (and this one seems hotter).

I think we have a gravity system with a tank of water upstairs (brown water so I assume this is the radiator water?)

What do you think could be causing the relative high pitched pulsating sound?

Many Thanks


Dear Graham:

From what you described in your hot water radiator system and the high-pitched sound that you are hearing when the heat initially comes on, I would suggest that you first check to see if the expansion tank on your system has failed.

Hope this is helpful.


Dear Graham:

From what you described in your hot water radiator system and the high-pitched sound that you are hearing when the heat initially comes on, I would suggest that you first check to see if the expansion tank on your system has failed.

Hope this is helpful.