The Float valve, a device similar to a hollow ball, is installed within the cooler tank. Whenever the water comes below its minimal level, the float valve detects it.
The water flow begins into the tank with the help of a water pipe connected directly to the tank via a hose connector.
Similarly, when the maximum water level is reached, it stops itself and prevents the flow of water.
It is an automatic mechanism, so you won't have to refill the water tank manually.