Plastic 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.

plastic
fictile: capable of being molded or modeled (especially of earth or clay or other soft material); "plastic substances such as wax or clay"
generic name for certain synthetic or semisynthetic materials that can be molded or extruded into objects or films or filaments or used for making e.g. coatings and adhesives
capable of being influenced or formed; "the plastic minds of children"; "a pliant nature"
A synthetic material made from a wide range of organic polymers such as polyethylene, PVC, nylon, etc., that can be molded into shape while soft and then set into a rigid or slightly elastic form
Credit cards or other types of plastic card that can be used as money