Do you have cold spots?
Is your system gurgling?
If your answer is yes to either one then you could have air in your heating system..
To bleed your radiators you first need a bleed key. Some radiators have flat head screwdriver slots, so this can be used instead of a bleed key.
You first need to turn off your boiler, no matter if its a combi boiler or heat only system. Once you’ve established that the central heating pump has stopped running you can start. The best place to start is downstairs and continue to the upstairs until all of your radiators are full. If you live in a single story building then start at the furthest point away and work your way back.
To do this – slacken of the bleed nipple within the radiator. You will either hear air coming out or see water. If you have air then continue this process without removing the nipple until you have water. Once you have, water shut down the nipple and repeat the process across you system.
If you have a combi boiler you will need to top of the pressure of the boiler as this will drop everytime you bleed a radiator.