• Danni Greenough

How To Bleed A Radiator



Radiators are an essential part of homes in the winter, warming rooms to a comfortable level and warding off the cold from outside. They are one of those things that we can't help but take for granted - but they still require some maintenance to keep them working well.


Why do I need to bleed my radiators?

Radiators are linked to your central heating system, which sends warm water flowing through them, in turn warming up the air around you. If air gets trapped in the pipes, it can prevent the water from flowing and takes far longer to warm up the room. You will tend to notice trapped air when you can feel the bottom of the radiator is warm but the top is still cold, and there may be the occasional gurgling noise which is irregular air pressure causing vibrations. By bleeding it, you are releasing the air and allowing the water to move freely again. This will not only save time but also money as it's working more efficiently again and reduces your energy bill.



What do I need?

Most radiators - especially older ones - come with a key. If you don't have one and it doesn't look like it can be turned using a screwdriver, you can easily source one from a local DIY shop or online. Along with the key you should have a large towel and a container or bowl of some sort to catch any water.


How do I bleed my radiators?

- When you've identified which of your radiators do need to be bled, turn the heating off and make sure you let them cool. Make sure you only bleed those that need it; if you do it to a radiator that doesn't have any trapped air you could end up lowering your boiler pressure far too much.

- Spread the towel on the floor underneath the radiator and set the container underneath the valve to catch any excess water.

- Fit the key (or screwdriver) to the valve and turn it anticlockwise. Only a quarter to half a turn at most - this will be more than enough, as opening it fully will allow water to potentially spill everywhere and drastically lower the boiler pressure. Once turned you should hear a hissing noise; this is the air escaping.

- When the hissing has subsided and a steady stream of water comes from the valve, it's time to tighten it back up again quickly to prevent too much water coming out.

- Repeat the steps for all the radiators that require bleeding, and then check your boiler pressure. It should show between 1.0 and 1.5 bars when off and around 2.0 when on. If it's too low, use the filling loop to top it up - if in doubt, contact your local engineer who will be able to help. (Always remember, when seeking professional help, companies need to be Gas Safe registered to be able to work on boilers.)

- If the pressure is right, heat up your radiators and check to see they're working correctly. (If you have a cat they'll soon let you know!)



My radiators upstairs aren’t getting hot! Do I need to bleed them again?

Once bled, you shouldn't need to do it again for a while. If you haven't already, check your boiler pressure to make sure you haven't lost too much.

Why does my radiator feel hot at the top and cold at the bottom?

Unfortunately older radiators are subject to corrosion, so this is most likely rust and dirt that has built up inside over the years. The way to combat this is to take the radiator off the wall and flush it through - we recommend contacting an engineer to do this.

How often should I bleed my radiators?

You should really only need to do it on a semi-regular basis - once every two months or so. If you find yourself doing it more often, or are finding leaks or patches of damp or rust, call in an engineer.


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