Pentair Sta Rite MasterTemp 250 Natural Gas Orifice (460739) aquaflo The Pentair 25023 0160S DE grid The Pentair 25023 0160S DE grid replacement filter is intended for compatible DE filter applications where a worn internal grid needs to be replaced The Val Pak generic 1 inch slip spring return line check valve is designed for compatible return line plumbing where a smaller slip connected valve is needed to maintain one way water movement It is used when the heater requires the correct natural gas specific component for combustion service or conversion related work The right orifice helps the burner system receive the intended gas flow for the model and fuel type