Hydrologic Float Valve 20+ GPM for Big BoyThis Hydrologic Float Valve is built to control the water flow in your Big Boy reverse osmosis filtration system. It automatically determines the water level in the storage tank of the purifier and helps you ensure that your filter remains full at all times. Since its made using PVC, it is heavy duty and has high corrosion resistance. If the water level gets below the pre set level, this NSF approved valve opens automatically and reduces the float of