Originally Posted by Cpt_Kirks
Will a 90 degree elbow on the bottom (inlet) cause issues with the air rising through the pump?
No, or probably not anyway. It is generally recommended to not have elbows positioned within 5 pipe diamters of the pump inlet for optimum performance. It's a minor thing and that distance would only be a couple of inches or so for a 1/2" inlet. The elbow should not affect priming the pump.
IMO, the inlet/outlet positions don't much matter if you use a bleeder valve and have a reasonable amount of positive suction head.