Draining a central heating system, especially pumped central heating systems, is a crucial part of maintenance that will need to be done throughout the lifespan of a central heating system. These systems use water as the medium, where water is heated and delivered to central heating radiators through copper pipes. Draining a central heating system is done as a means of cleaning the system. Below are tips for how to drain a central heating system.
How To Drain A Sealed Central Heating System
A sealed or vented central heating system will need to be drained if the valve is broken or malfunctioning and needs replacing, or the system needs to be maintained, or you intend to get a new boiler installed, or you wish to install extra central heating radiators to your system. For a guide on how to drain down a central heating system, read on.
1. Switch off the boiler or stopcock (or drain cock), or cut off the water supply that leads to the feed and expansion tank of the central heating system. This can be done by placing a block of wood on the tank, and then affixing the ball valve there by tying it. With some central heating systems that are sealed, there is a tank referred to as a make-up tank, and this is a lot like the feed and expansion tank that only exists in systems that are vented. However, the two systems differ in that in the make-up line, there is a non-return valve that works to inhibit the expansion of water to the tank, as the water heats up.
2. If there is a filling loop that fills up the system from the rising main, you will need to ensure that the valve for the filling loop is not open. Next, find the system’s stopcock or drain cock. This is often within the return pipe that is in close proximity to the boiler, or it could be on the boiler. Another possible location for this is beneath the floor, at the very bottom.
3. Get a hosepipe and attach this securely using a hose clip. One end should be around the exterior of the drain, and then unseal the drain cock. It’s ideal to use your drain cock key for this, but an adjustable spanner should do.
4. Begin the draining process by unsealing manual relief valves, until water has been completely drained out. Once the flow of water stops, unseal each and every bleed valves of the radiator beginning from the top. Any remaining water should then be let out by air. How long to drain central heating will depend on how much water is left.
5. You can also check the water’s color to identify any problems with your central heating system. A color that is gray (like dirty water) is fine. If the water that flows out is black, it is possible that there is sludge in your central heating system, while rust-colored water is a sign of corrosion.