How To Replace A Damaged Radiator Valve
If your radiators aren't working properly it's possible that you have a damaged radiator valve. Replacing the valve is a difficult job, but it's not beyond the abilities of an advanced DIY-er. Lets see how to get that radiator fixed!
Step 1: Drain The System
To replace a radiator valve, first drain the system. If you have a combi boiler, you can do this yourself. But if you have a conventional cylinder tank system, you will need to call in the professionals to do this.
To drain the system, connect a hose to the drain cock which is normally found at the lowest point in the pipework. Use a jubilee clip to secure it. Place the other end of the hose outside to discharge into a gulley and open the drain cock. Wait until all the water has left the system before you start on the radiator.
Step 2: Unscrew capnuts
Close the valves and lay your rags underneath to catch any water left in the system. Holding the body of the valve with a wrench, use an adjustable spanner to unscrew the capnuts and lift the valve from the end of the pipe. Next, unscrew the valve cap-nut and remove the old valve before giving the pipe a thorough clean with wire wool.
Step 3: Unscrew Valve
Unscrew the valve adaptor from the radiator. You may be able to use an adjustable spanner, depending on the type of adaptor, or may find you need a hexagonal radiator spanner.
Step 4: Clean Threads
Wind PTFE tape four or five times around the threads of the new adaptor and screw it into the end of the radiator. You can buy PTFE from DIY stores.
Step 5: Fit the Valve
Fit the new valve but don't tighten the cap-nut yet. Holding the valve body with a wrench,align it with the adaptor and tighten the cap-nut that holds them together. Then tighten the cap-nut that holds the valve to the water pipe.
Step 6: Refill the system
Refill the system. Find the filling loop which will be just underneath the boiler. Turn the valve, and increase it until the pressure gauge reaches 1 1/2.
Step 7: Bleed the radiator
See "How To Bleed A Radiator" for advice on how to do this.
Step 8: Refill the System again
Once you have bled your radiators, turn the filling loop valve on the boiler again, and increase it until the pressure gauge reaches 1 1/2.