Under Basin Thermostat (15mm) from manufacturer, Home of Ultra, is designed to provide safe water supply to outlet. TMV3 approved valves are easily incorporated under a sink or in a convenient location, work by sensing the temperature of incoming hot water, then thermostatically blending a constantly variable amount of cold water to the hot water feed - thus achieving a selectable maximum temperature setting. Once installed and set, the valve operates automatically, monitoring temperature as soon as a tap is opened.For best results hot and cold water supply should be at equal pressures. providing safe, anti-scald bathing and showering options for your bathroom.