Culligan Whole House Water Filter For CulliganInstalls easily on 3 4 in. main water line, includes P5 filter. After installation it is recommended that you prime the bypass valve before turning the water back on. To do so, use the handle of the housing wrench (which also serves as a key for the bypass valve) to rotate the bypass dial back and forth 180 degrees 10 12 times. Due to how the housing is assembled and transported across different climates, the bypass can freeze up making it very