Cock Valve H Type is a simple, economical, and trouble free design… time tested in applications around the world over many years. This type of strainer is actually a high quality, pressure rated plug valve with integral straining filters. Switching the flow from one filter to the other is accomplished by moving the operating handle through a 90 degree arc. The design is such that is impossible for this operation to stop the flow because of the unique port design in the diverter plug. The plug is automatically positioned each time in exactly the right spot by integral stops.