A float valve is a simple device that automatically controls the flow of water into your water trough. It consists of a float (usually made from plastic or metal) that rises and falls with the level of water in the tank. As the water level decreases, the float lowers and opens the valve to allow more water to flow in.

A water tank float valve, also known as a float valve or ballcock, is a mechanical device used to control the level of water in a storage tank, such as a a livestock watering trough, stock tank, or water storage tank. Through the principle of buoyancy, it regulates the flow of water into the tank to maintain a consistent water level.