The rubber flapper is installed at the purge end of the Pump Protection Separator. The raised internal lip end, goes over the notched groove in the separator and with the natural fold on the flapper perpendicular ("criss-cross") to the retaining bar in the purge outlet of the separator. Use the clamp gear supplied to secure the flapper in place.
Sand accumulates in the separator when closed. When the flapper valve is open, sand discharges deep into the well.