radiators.
after that, the central heating system can be shut down letting any air or water from getting driven around the system and waiting 10 minutes for everything to get cooled down.
the radiator which is nearest to the boiler needs to be operated by turning off the radiator valve and placing the tray below the bleed valve, make sure you keep a large towel in your hand.
then locate the bleed key on the bleed valve and slowly turn it to left till water comes out and not air. it is very important to keep in mind that the bleed valve should not be opened completely as there are chances that it 