Mixer and Thermostatic Valves

A mixer valve blends hot and cold water supplies into a warm flow for your shower.  Most (but not all) have a thermostat to maintain a set temperature for the shower water, which can be adjusted up or down to provide a comfortable showering experience.  Your household water pressure needs to be reasonably high for the thermostatic shower to work properly, but if this is a problem, pressure can be improved by using a pump.