How do I know if I need to bleed my radiators?

If your radiators are cold at the top but warm at the bottom, this is a sign that you need to bleed your radiators. Water is heavier than air so the trapped air will always be at the top of the radiator and the air is stopping the warm water reaching the top of the radiator leaving them feeling cold. 

If you can hear gurgling noises coming from your radiators that could be an indicator that there’s air trapped in the   system. 

Over time radiators can drop in performance and air can get trapped and stop water from circulating. Regular  maintenance on them (bleeding them) keeps them working efficiently and effectively. Poorly performing radiators means higher energy usage and as a result, higher bills.

It’s a good idea to bleed your radiators when you turn your heating system back on after the summer months, so that they are working efficiently during the Winter months.

You will need a radiator key to bleed the radiators, which you can buy at any hardware store.

Switch off your central heating

Let your radiators cool down a bit before you start bleeding them - water will be released when you’re bleeding them so you need to ensure the water isn't scolding hot.

Use the radiator key

You need to find the bleed valve on your radiator - it is a small metal square inside a white round nut that will usually be located on the side of your radiator. If you're not sure if it is the correct one, check the radiator key against it and if it fits over the nut then it's the right one.

Release the air

Put the radiator key over the bleed valve and turn anti clockwise slowly to release the air - always have a towel or something underneath the valve to catch any escaping water.

You should start to hear air escaping, and feel the warm water rising up inside the radiator. As the water rises and the air escapes, the water will reach the top of the radiator and start to leak out of the bleed valve. At this point, turn the bleed valve clockwise to close it again.

Be careful not to overtighten the valve as you could damage the thread.

Check your boiler pressure

If you have a combi boiler, check the pressure of your boiler after you’ve bled your radiators as this can cause a drop in pressure in the boiler. On a combi boiler it should be between 1.0 & 1.5 bar - the pressure gauge will be on the front of the boiler.

If the pressure has dropped, turn the boiler off for around 20 minutes to allow it to cool down. This ensures the   pressure reading is accurate and makes sure the water is not scolding hot in case of any leaks or steam.

You will now need to find the filling loop, which is a silver hose with valves at each end and is usually situated        underneath the boiler.

Open both valves slowly and you will be able to hear water running into the boiler - at the same time keep an eye on the pressure gauge and when it reaches between 1.0 & 1.5 bar, turn the valves back off, one at a time. Do not over fill as this may cause other issues.

Some boilers might have a filling key or an easy fill lever instead of the filling loop - check your manual for details.

Turn the boiler back on.