What is the function of an Altitude Valve on a water tank?

An altitude valve functions specifically to manage the filling of a water tank. Its main role is to close when the water level in the tank reaches a predetermined high point, effectively preventing overflows by stopping the inflow of water. Once the water level drops to a lower set point, the altitude valve opens again to allow water to refill the tank. This mechanism is critical for maintaining consistent water levels within the tank, ensuring that adequate amounts of water are available for distribution while preventing waste and potential structural damage from spills or overflow.

Other choices relate to functions that are not associated with altitude valves. Regulating temperature does not fall within the purpose of an altitude valve; it primarily deals with water levels, not temperature control. Monitoring water quality is typically handled by different types of equipment or sensors designed for that specific purpose. Lastly, preventing evaporation is not a function of altitude valves; rather, this task would involve tank design aspects or covers, but not the altitude valve itself.