Draining water systems
If you wish to move a radiator or need to do some repairs, first you need to drain the central heating system. At the lowest point in the system (often on a radiator) there should be at least one draincock that allows you to drain the water. You might find others by the boiler or in other pipes..
To drain the system, first you should turn off your boiler or other type of water heater. Then turn off the mains stopcock located inside your home (more about how to locate the mains stopcock). You shouldn’t have to turn off the water company’s stopcock, but you might as well to be on the safe side.