Mixer showers require a cold water supply and a hot water supply from either a Hot Water Cylinder or Combination Boiler. Dependant on your hot water supply, they can offer much greater water pressure then an Electric Shower, but they will require your Boiler to be switched on. There are two main types of Mixer Shower - Concealed Valves and Exposed Valves. Concealed Valves are designed to be recessed in a tiled wall, concealing all the pipe-work and most of the Valve. An Exposed Valves is mounted on top of the tiles, exposing all the pipe-work and connections. Exposed Valves are commonly used on solid outside walls, and Concealed Valves can only be used on internal timber walls.