Know precisely when your backwash cycle is finished without guessing or letting water spray from the waste port. Constant UV exposure and pool chemicals eventually fog, craze, or crack original plastic viewports, obstructing your line of sight and causing drips along the threads. This factory-threaded clear window screws right into the side of your valve body, using the included fresh rubber gasket to lock down a high-pressure seal so you can check effluent clarity at a glance.