How to drain the central heating water out of a Vaillant combi boiler.

How to drain the central heating water out of a Vaillant combi boiler. (My boiler was losing pressure, so I checked a few things and worked out that the Schrader valve had stopped working properly in the expansion vessel. So I needed to empty the water out of the boiler to replace the valve.) TURN OFF THE POWER TO THE BOILER: Open the front cover. Turn off the power. Turn off the power at the wall switch too. Close the front cover. DRAIN THE WATER OUT OF THE BOILER: Isolate the boiler from the rest of the heating system by turning off the drain valves with a 4mm Allen key, so that the slot is pointing across the pipe. Attach an 8mm diameter hose to the drain valves and use a bucket to catch the water. Open the drain valve using an 8mm ratchet spanner. Wait forever...