A thermostatic tap is a faucet designed for home use which regulates the temperature of the water it releases. These taps maintain a constant ratio between cold water and hot water in order to keep the total temperature the same. They are used both for convenience and as a safety device.
Function - Thermostatic taps keep water at the same temperature. This does not mean that the water is always the same temperature, however. The tap can be adjusted to release colder or hotter water, but once the balance has been adjusted at the faucet, the thermostatic tap ensures that the water temperature will remain at that specified temperature.
Purpose - Thermostatic taps are designed for comfort, so that when you are washing your hands or taking a shower, the water does not suddenly become hotter or colder. They are also a safety feature, since a sudden surge of hot water can scald you. Thermostatic taps prevent such surges.
Complex Adjustments - Thermostatic taps actually compensate for other flowing water in the house or building. If you are taking a shower and someone else starts the dishwasher, it will affect the amount of water available for the shower. Thermostatic taps compensate for the hot or cold water that other appliances and devices are using to maintain constant water temperature.
Decreasing Flow - The way thermostatic taps compensate for other water usage is to decrease flow. If a toilet is flushed using cold water, for example, a thermostatic tap in the shower will also cut back on the amount of hot water it uses. This means the water pressure can sometimes suffer in a thermostatic tap, but it is very reliable in maintaining temperature
Use - Thermostatic taps can be used in sinks and showers to regulate and maintain constant water temperature, and can even be installed in toilets to prevent condensation. Their most common use, however, is in the shower, to maintain a more comfortable and safer experience.