Idiots guide to bleeding radiators please

[Allnewtometoo]

I realise this is probably a very straightforward process, but it's one that I have an irrational fear of. I have 2 cold radiators (one up one down) and one not very warm.

All I know is you put the special key into the airlock and turn it. When water comes out then turn it back. You usually only need to do a quarter or half turn. Be careful if the heating has been on as the water will be scalding so take a cloth and small bucket with you.

I've only watched X though.

Get a key.

There is sometimes a plastic dial on the top of the bleed valve that allows you to direct the water. So turn this in the direction you want the water to go.

Get a cloth and turn the heating on, then loosen the valve with the key. You will hear a hissing sound as the air comes out. When the water comes out you can turn the valve back to close it.

Do not take the key out of the valve as you bleed, because it will take some time to get the key back in position on the valve and in that time you might find a hell of a lot of water has come out. Just hold it in place while the air comes out and turn it back when water starts to flow.

Make sure you have something like a cloth to catch/absorb the water. The water is often dirty and if you just let it out it may hit the walls and stain your paintwork/wallpaper or carpets.

Bleed the highest radiators on the system first. For two reasons. one is that these are where all the air will collect. Two because you will be able to practice opening and closing the valves without having water come out.

After you have bled the system you may find that you need to re pressurize it depending on your system type, so make sure you know how to do this before you bleed, otherwise if you don't then you may take the system pressure below the working point of the boiler and it may stop working.

Finally if you are worried about any of this get the engineer to show you how when they do the yearly boiler service. They are normally happy to help show you how. Youtube videos are also available to watch.

Bleeding the radiator may not help, radiators holding excess air are still warm at the bottom but cold at the top where the air is. If the rads are fully cold, you probably need to look into balancing the system.

Edit - I see some people say it is important to switch off the system. Not quite sure why. But maybe get some advice on this. I always do mine with the system switched on ! Maybe someone can explain why it is important to switch it off.

Gaspanic has a great instruction list, except do it with the heating off - and having been off for a while so the water isn't scalding.

There's bleeding, or balancing, or clearing the sludge out of the system. So it may not work by simply bleeding. Youtube is your friend here.

A lot of boiler cover plans will cover radiators so if you have a plan check that.
Stupid question but are the valves turned on? Does the pipe to the radiator get hot or not? Are the two radiators next to each other in the system or in separate parts of the house? If it's air you'll find the. Bottom gets hot but the tops cold. You get a key and slightly open the valve, have a towel and bowl ready. When water starts to come out shut the valve. Be careful as the water is likely to be very dirty and sludgy so really work quick with the towel to make sure if doesn't get into your walls or floor. If no air comes out you will have an issue with the actual system or radiator ans that's probably a job for a plumber. They can flush the system as it might just be those radiators have a sludge build up in them. It's like a black/brown goo that somehow gets into the system. Good luck

Edit - I see some people say it is important to switch off the system. Not quite sure why. But maybe get some advice on this. I always do mine with the system switched on ! Maybe someone can explain why it is important to switch it off.

You should do it with the heating off and radiators cool, as if the system is on, the water is going to be very hot.

This from the British Gas website:

No! It’s very important to make sure your heating is off, and the radiators are cool before you bleed them. This is because radiators are filled with water and air, which is what escapes when you open the valve (include link to new pressure release guide page). When the heating is on, the water and air inside become dangerously hot – so you could scald yourself when it’s released.

Do it with the heating off, I use the washing up bowl to collect the water. You'll probably need to repressurise the system afterwards, YouTube will show you how to if you search by make and model.

If it's cold at the bottom it's likely to be sludge
Cold at the top likely to be air in the system
Cold all the way through either you've thermostatic twisty thing is off or you need a plumber.

If you’re just bleeding the air out then you shouldn’t have any water coming out ? Maybe a couple of drops when you turn the key back to closed but you definitely don’t need a bowl ? You just turn the key slightly and listen , you can hear when the air is out . Only turn the key a little bit and then key your hand on it to shut it back off when you hear the sound change.

@Diyextension you've obviously never dropped the key, fumbled around finding it and ended up with water everywhere.

I agree you don't need bowl. Turn it a tiny amount and you will hear air. When all the air is released a tiny amount of water will come out. I normally have a couple of square of kitchen roll ready but there won't be much water if you only turn it a small amount and be ready to turn it back.

I use Youtube to answer almost everything like this.... I'm a very visual person, seeing is believing.

Here is a youtube clip

Thank you all. I've just been round And had a feel of all the radiators.

Hallway (downstairs, front of house) completely cold, but pipes warm.

Top Of stairs, (middle of house) hot at bottom , cold at top.

Bathroom - upstairs, back of house. Cold. Cold. Cold. Cold pipes too. Towel rail is hot.

So presume top of stairs needs bleeding. Hallway maybe too. But bathroom may need a plumber. 😭

It depends. If your bathroom is last on the loop then there might be too much air compared to water. Get bleeding, top up boiler if necessary, put on heating for a bit to check rads, bleed a second time and top up boiler.

I had a new boiler fitted and we had to bleed the rads four times over the space of a week before everything was "right" again so don't panic about a plumber yet.

The radiators that have hot pipes - open both valves a bit on the bottom. One side will be easier than the other - you might need a spanner.

Yes to bleeding then running then bleeding. Then see how you go.

I've always bleed radiators when the system is cold. I'd do one at a time, maybe starting with the one that's receiving some hot water.

Not sure if you'll need to do it or not, but note the pressure on the boiler when cold and if it lowers a bit after bleeding. If so, don't forget to top the system up with water.

I'd insert the key and turn is slowly, a notch at a time until you hear air. When the first drop of water comes out, it's aired.

I'd bleed them all if there's three op can't remember what order you should go it in though, google should help. If it doesn't work it's plumber time I'd say if some of the pipes aren't hot to the radiator

because otherwise the water that comes out might be boiling hot! Surely that's common sense!

I appreciate it sounds like you put the heating on and then do it immediately so it might not have much time to warm up in your house, but this is dependent on how quickly your system works and how many radiators you have to do. If it heats up quickly and you have a lot of radiators the last ones could be very hot. Mine get from 0 to too hot to hold a hand against in less than 5 mins.

Placemarking.