The Pool Sentry Automatic Water Level Control is used to maintain the proper water level of a pool, spa or pond automatically and unattended. With a low-profile physique, the Pool Sentry stays out of sight and out of mind while efficiently maintaining proper water levels in your pool. As the float drops, the water turns on. When the float reaches its highest point, the water shuts off. It works very similarly to the float valve in a toilet tank. The user can adjust the float any desired level.