This is a Hayward ECX4077B1 Check Valve for Perflex Extended-Cycle DE Filters, EasyClear and StarClear Cartridge Filters and ReGenX Grid Element DE Filters.
The Hayward ECX4077B1 check valve allows water to flow into the filter while preventing back-flow. If water is flowing from your filter back to your pump, inspecting your check valve should be job #1.
This part is used on several Hayward filters including Easy-Clear models, the Perflex family of filters, the Regenx, ASL, and Star-Clear.
Please refer to the schematic links for a full part listing of your filter!
