There are two ways of flushing a radiator, either getting a plumber in to professionally power flush your whole central heating system, or doing it yourself and flushing a radiator manually. If you choose the second option then you will need to know how to remove a radiator.
When a radiator is full of sludge then the contents can make this job very messy so ensure that you’re fully prepared to clean up any spills but don’t let this put you off as if you do it right then you shouldn’t have a problem. Other items you will need are:
Make sure that you’ve turned your central heating off and let it cool down as you don’t want to be dealing with hot water when emptying the radiator. Next place the old sheets and towels under the radiator and especially beneath the valves and around the pipes coming through the floorboards.
Next you will need to isolate the radiator by turning off the valves on each end. First turn the the Thermostatic Radiator Valve (TRV) to it’s fully off position. At the other end of the radiator you will find the lockshield valve which will usually have a plastic cover over it. Remove the plastic cover and using an adjustable wrench turn the valve fully clockwise making note of the amount of turns it takes. You will need to reset the valve by the same amount when you replace the radiator to ensure it’s properly balanced. Your radiator is now isolated from the central heating system.
Place a bucket or bowl under the thermostatic valve and using both the adjustable wrenches, place one wrench over the body of the valve and use the other to loosen the nut that connects the radiator to the valve. See the diagram to right to an idea of what you have to do.
4. Open the bleed valve
Ensuring that you’ve got the bowl and the sheets below the valve you’ve just undone it’s time to open the bleed valve using your radiator key which will break the vacuum in the system and allow the water to flow out and into the bowl or bucket. This is when you get to see how dirty your water is and how much sludge is in your radiator.
5. Open the lockshield valve
Now it’s time to do exactly the same to the lockshield valve and you should be able to tilt the radiator to remove any excess water in it. Lastly use the radiator key to close the bleed valve which should reintroduce the vacuum in the radiator. You can now remove the radiator from the wall but be careful of any sludge leaking out the radiator so it might be useful to tape some sandwich bags around each of the valve ends.
To replace the radiator wrap PTFE tape around the threads and tighten the valves on each side.