Bleeding A Radiator

[Spreeny]

Should the gas central heating be 'switched off' before I try & bleed a radiator that's cold at the top please? ....Tia

[Baldric]

Yes

[donny48]

It is better to switch off.

[B00]

Mr Boo didn't when he did them the other day? Can we expect a problem?

[donny48]

No problem, just the way I was taught.

[Old_Geezer]

Not unless he's already scalded himself.

[yogi-bear]

No, you should be fine Boo, it's only as a precaution not to have very hot water coming out when you bleed them, but preferably should do it whilst off. x

[Spreeny]

Thank you very much .... Too cold to switch heating off at the mo, so might leave until the morning now

[tonyav]

I have always found it better to bleed them with the heating on.

[Gizmonster]

You don't really need to turn it off, but just be aware if it is on, then when you do bleed the radiator, you're running the risk of scalding yourself when the water starts coming out.
Also, when you've bled the radiator, there's a chance that you might have to top the boiler up using a filler loop .... depending on how much bleeding the radiator requires.

[Prudie]

We do our bedroom one nearly every week when it's on and just wrap a cloth round our hands. If you go gently you can stop the second air changes to water. Don't you need the pump running to effectively get it all to come out?

[tonyav]

Don't you need the pump running to effectively get it all to come out?


That is why I have always bled radiators with the heating on, Prudie.

[yogi-bear]

We have a Baxi...... I've always bled them with system off and radiators, at least, luke warm, before bleeding...scroll down to 3. Prepare ....they agree.

It's just so easy to scald yourself, if you're not careful, and it will severely burn your hands and fingers.


http://www.baxi.co.uk/information-and-advice/heating-advice/heating-system-maintenance/how-to-bleed-your-radiators.htm

[Old_Geezer]

I'd hope gravity feed would allow you to bleed a cold system, but I guess a pump helps.

[SnookerPlayer]

Hot or cold, does not matter. Just don't fully unscrew the bleed nipple.

[yogi-bear]

Snooks,

If you do that whilst hot and on, you're not getting all the trapped air out.

If you attempt to bleed them with the pump working, because of the hot water circulating around, then more extremely hot water will flow out, go on your carpet, if you have one, and probably stain, not to mention risk to your hands if cloth not covering completely, when you start to open up the nipple.

From Wiki how:

Turn off your heat. Ensure that your central heating is switched off before bleeding, as an active heating system can introduce more air into the system. You want your radiator's contents to settle completely before releasing the air trapped within. Allow time for the heat in your system to dissipate, then feel all over your radiator for heat. If any part of your radiator is still hot, wait for it to cool completely before proceeding to the next step.

I think whatever works for you, should go with....It's only my opinion :-)

[bhg481]

The best thing is to put rust inhibitor in your system and then you never need to bleed it.
The last time I bled my system was 1996 when I added extra radiators.

[cleggie]

ok
you bleed them with boiler and punp off.
reason is air in system rises to top of radiator when off.therefore when you bleed them the air is at the top and comes out first.then when water starts coming out there is no air left in radiator.if you bleed rad with punp on its continually circulating any air so its still in system.hope this clears it for you

[bhg481]

In most domestic central heating systems the inlet and outlet for the water are both at the bottom of the radiator. The gas (hydrogen, not air) doesn't circulate, it's actually produced in the radiator when the steel radiator corrodes and it stays in the radiator it's produced in. At the same time the corrosion process produces black iron oxide, known as sludge, which builds up at the bottom of the radiator and, eventually, impedes the water flow causing the system to require flushing.
It doesn't really matter whether or not the pump is running when you bleed the system but it's probably safer if the heating is off in that the risk of scalding is reduced.
Incidentally, the hydrogen released when bleeding the radiators is inflammable so, if you're a smoker, don't whilst you're bleeding.
As I said in my earlier post, adding a corrosion inhibitor to the header tank stops the radiators rusting and so removes the need for bleeding.

[mikey4444]

I bleed the rad in my bathroom on a weekly basis and sometimes I forget to switch the pump off, as I was taught by my Dad many years ago......but it doesn't really seem to make much difference either way !