Emptying a heating system
Emptying a heating system
A fully pumped central heating system can be drained to enable work to be carried out. To work on a radiator problem or to extend the system maybe. This is often executed by the heating engineer during repair or extension work although some experienced homeowners have been known to drain their own heating systems.
Cleansing the metal radiators is the most standard driver of this activity. Before any work is attempted you need to turn off the water heating pump and gas fired boiler. It is also critical that you do not let any more water into the heating system while you flush it.
The header or expansion water tank in the attic is used to normally top up the system with water. A ball valve mechanism, as used in toilets, is used in the expansion cylinder to influence the current of water. Rising water levels in the tank mean that the valve is blocked as the ball floats higher on the water surface. Water is added to the central heating system if the levels fall as the ball will drop on the water surface venting the valve. To fully empty the gas heating system this top up process will need to be stopped. Placing a small plank of wood across the water cylinder stopping the ball-valve from moving will check further water going into the gas central heating system.
When you are confident that you are prevented any further water entering the gas central heating system you should connect a hose pipe to the outlet valve at the bottom of a metal radiator taking care to ensure the end of the hosepipe is in a flush outside your property. Water can now enter the outdoors clear my flowing through the hose out of the radiator valve. Obviously, if you want to empty the whole gas heating system you will need to connect the hose pipe to one of the level metal radiators. Check now that no water is entering the gas central heating system and that the heating radiators are fully drained before you do any further work.
To make your central heating system empty faster you should vent any bleed valves on your radiators, starting with the metal radiators on the top story and working your way down. You can commence work on the gas central heating system once all the water has emptied out.