Bottom Entry Part 3 Ball Valve 1/2" is used to fill water tanks such as toilet cisterns from the bottom. It is designed to be used in conjunction with a ball float. The ball float rises as the water rises and when a specified level is reached it causes the one way valve to be activated and shut off the water entry. The part 3 valve is plastic and bent with the outlet on top so is above the cistern overflow level. It has better backflow prevention and has a ½” connection.