You can flush a gas heating system
At some moment in the life-time of your fully pumped heating system you will need to drain it. To exchange heating radiator valves or add an additional heating radiator as an example. This is often carried out by the engineer during repair or extension work although some experienced homeowners have been known to flush their own gas central heating systems.
In most situations Emptying the central heating is executed to clean the radiators. The first measure you should take is to switch off the boiler and central heating pump. To successfully complete this job you also need to check that no more water enters the central heating system. If you have a gas boiler care plan such as British Gas Homecare you might want to get hold of your provider to understand what services they provide.
The expansion water tank in the attic is used to normally top up the system with water. The expansion cylinder uses a ballvalve similar to that in a toilet system. As the water reaches maximal level the ball floats on the surface and shuts the valve. However when some water is pulled off the cystern, the ball drops, the valve opens and more water gets into the cystern. To ensure that the gas heating system fully empties we need to stop this mechanism.A good reference for detailed articles can be encountered at this site where one will see several conscientious articles. Using a metal or wooden rod to prevent the ball leaves are falling in the cystern will stop water entering the system as the water is flushed.
Once you have accomplished the above run a hose pipe from an outside clear to the outlet of at the bottom of one of your metal radiators. The gas central heating system can now empty by water flowing out of the heating radiator, through the outlet valve, and into the external empty. The hose pipe needs to be attached to the lowest point in your central heating system which will be one of the ground floor heating radiators. Be patient and ensure that all water has emptied from the gas central heating system and no more water is getting in before you begin any further work.
By venting the bleed valves in the radiators on the top story you will help air to enter the gas heating system and speed up the Flushing process. Work can begin when all the water has drained out.