Mixer showers differ from standard showers in how the hot and cold water is delivered through the system. A mixer shower uses a special valve that mixes the hot and cold water together in a small chamber before it is ejected out of the shower head.

This type of shower can be used in a system with high or low pressure, but each specific shower must be checked for its pressure requirements.

A mixer shower can be either surface mounted or flush mounted. A surface mounted fixture is installed easily over any existing surface. In a flush mounted fixture, only the valve and shower head are visible, while the rest of the piping is inside of the wall. Flush systems are best installed in a new shower construction, while a surface mounted system is easily installed in an existing shower room.

In addition to the standard mechanical mixer shower, there is also a thermostatic mixer shower. The thermostatic shower uses a built-in thermostat to sense water temperature and make slight changes in the mixing valve to ensure it remains constant. In drastic situations, the thermostat could even shut the water off completely if the temperature gets too high or too low.

For a mixer shower to work properly the hot and cold water lines must have the same water pressure, otherwise the one with the highest pressure can take over in the mixing. Both the hot and the cold can come from the mains in a combi boiler situation or a water heater/cold main situation, or they can both come from a tank system with a cold storage and immersion tank. In cases where one line is high pressure and the other line is low pressure a special pressure-balanced valve can still be installed to even out the pressure and make the mixer shower workable.

In no way will a mixer shower increase the water pressure of the system or allow for a higher flow. Water will still be emitted from the shower at the same rate of flow as any of the other taps.

In some cases, a mixer shower can have a major downside when it is connected to water pipes that feed water to other valves, taps, or appliances. When the other water-using systems are activated and require a water feed, it will diminish the flow to the shower. As the flow diminishes from one of the water lines, the mix of hot and cold will become skewed so that the temperature of the water coming out of the showerhead will temporarily become colder or hotter until the pressure is once again equalized. To fix this, separate pipes have to be installed so the shower is on two independent lines directly from the mains.

Because of these special circumstances, a professional plumber may be required to install the mixer shower. Additionally, mixer showers cannot be pumped from combination boilers, multipoint heaters, or other mains pressure system.