Brine Tank Float Valve

float valve
A mechanism that regulates fluid level by using a float to control the filling of water in the water tank; used in swamp coolers to regulate water levels.
A ballcock (also balltap or float valve) is a mechanism, or machine for filling water tanks, such as those found in flush toilets, while avoiding overflow. The modern ballcock was invented by Joseph Bramah and Thomas Twyford.
A valve which is mechanically actuated by a float. Utilized on many cooling towers to control make-up water supply.

brine tank
The tank in which the brine solution is mixed and held. This is the tank you add salt to.