A thermostatic radiator valve detects room temperature and will control the heat level of the radiator to keep the temperature at a constant setting. Most have an off setting, a frost setting (for rarely used rooms) and then numbered calibrations. These valves can save you money and reduce your home’s carbon emissions from day one.
Drain Your Heating System - The first task is to drain your central heating system. It's better to try to fit all the valves in one go so that you don't have to drain the system more than once.
Unscrew The Adaptor - Put plenty of old towels or sheets around the floor. Hold the body of the old valve with one of the adjustable wrenches and use the other to loosen the nuts that hold the valve onto the copper pipe and to the adaptor that's fitted into the radiator. You should not be able to remove the valve. Unscrew the adaptor from the radiator. You may need to use a radiator valve, fitted inside the adaptor.
Fit The New Adaptor - Fit the new adaptor, cap nut and olive (the metal collar) onto the radiator. Clean the internal threads with a clean cloth and wrap some PTFE tape half a dozen times around the adaptor threads, winding it clockwise. Screw the adaptor into the radiator and tighten.
Remove And Replace The Olive And Cap Nut - Remove the old olive and cap nut from the copper pipe and replace with the new set. If the old olive doesn't slide off, carefully cut part way through the olive and break the pieces apart with a small screwdriver. Don't let the hacksaw blade touch the pipe.
Tighten The Cap Nut - Fit the thermostatic valve, then tighten the cap nut between the adaptor the valve, holding the body of the valve with one wrench. Finally tighten the cap nut between the pipe and new valve.
Refill The Heating System - Refill the central heating system and check for leaks. Set your living room valve to fully open and your bedrooms to a lower setting. You don't need to constantly change the settings as you use the rooms. If you have a spare bedroom, put the valve on the frost or minimum setting and keep the door closed so that the adjacent radiators don't try and compensate for the drop in air temperature.