The concealed Aquavalve has an ingenious bi-metallic coil which reacts quickly to changes in water temperature to ensure the water temperature always remains constant. This thermostatic shower precisely mixes the hot and cold water to create your desired temperature. There is also an integral anti-scale mechanism inside the valve to stop the build up of limescale - particularly useful if you live in a hard water area. However if you are unfortunate enough to have a compromised coil there is no need to replace that beautiful Aquavalve showering system! All is not lost with the Replacement Thermostatic Cartridge! When fitted into an Aquavalve valve the cartridge provides maximum temperature preset at 38 degrees Celsius and will automatically shut down should the hot and cold water supplies fail. If you wish to shower at higher temperatures then all you have to do is push the red button on the side of the shower it really is that simple and also excellent value.