Open vented systems central heating system systems might need to be drained for radiators and boilers to be mended or replaced, and some individuals do like to drain the system completely annually, as part of the final boiler heating upkeep.
One. Turn off the boiler and disconnect it from the power supply, or ensure the fire is out if it’s a solid fuel boiler.
Two. Switch off the water supply to the enlargement tank ( if you can’t find the valve simply tie up the ball cock with string ).
Three. Connect a hose to the drain cock and secure in place over a drain or gulley, and open using two pliers to start the water draining.
Four. Permit air to replace the draining water by opening the air bleed valves on the upstairs radiators, and then once the water level dropped repeat with the lower radiators.
Five. Once water has stopped exiting the hose attached to the drain cock, the system should be empty.