A mixer tap works by receiving its water from both hot water and cold water sources, and using a set amount of each to provide water of the correct temperature, explains HeyKitchen.com. There are a number of different plumbing systems that can be used to create this type of a faucet. One of the most common ways to build a mixer tap is to use a double-handled setup.
Unlike some sink set-ups that have two faucets for hot and cold water, a mixer tap dispenses adjustable temperature water from a single faucet. In a double-handled setup, there are two handles that correspond to hot and cold water so the temperature of the water can be adjusted. This is possible because a mixer tap has two different sources of water. When the handle for hot water is turned, more of the water flowing to the faucet comes from the hot water source and less comes from the cold.
Most mixer taps also have a pressure balance valve. This means the temperature remains at the specified level regardless of the pressure in either the hot or cold water sources. Without this type of fail-safe, excessive use of water from either one of the sources could result in a temperature imbalance.