MLV's H20 System suggests that the term "mixing valve" has the general application of meaning any device in plumbing that controls the mix of hot and cold water to provide a comfortable temperature. As shown in the H20 system below, high-pressure showerheads restrict the volume of water flowing through the pipe, like when a gardener sticks a thumb partly over the end of a trickling garden hose to make it spray further. As its name suggests, a mixer shower mixes a hot and cold water supply in a valve to reach your chosen temperature before it reaches the showerhead. It should be noted here that thermostatic mixing valves on your water heater are essential to prevent scalding and control water temperature at the delivery point.
