Installing a new above ground red lion effluent pump and looking at the schematics and see they recommend a gate valve post pump (for obvious reasons) as well as a check valve on the pressure side in addition to the check valve built into the pump head on the suction side. I can't wrap my head around why I need the two check valves. Additionally, I worry about adding unnecessary mechanical parts to the pressure side, as this is in the basement and any failure would be catastrophic. Any insight greatly appreciated. Please see diagram from manual below.