Gravity discharge PSI at tank bottom

Gravity discharge PSI at tank bottom   (01/30/2018, 10:19 AM)

I need to know what the water pressure will be when exiting a water tank (54”L x 32” Dia.) from a 1” discharge line (located 2" off the bottom) when the tank is ¾ full, ½ full and ¼ full. The tank will be at ground level.
The water will be pumped using a pressure sensitive pump, I just need to be sure that I have enough PSI leaving the tank entering the pump to ensure it is enough to activate the demand sensor in the pump.