Total Back Pressure (Outlet Pressure) is the Sum of Condensate Return Line Pressure + Equivalent Lift Height Pressure
Discharging condensate upward against gravity is the least desirable scenario; however, in certain instances, it may be the only solution possible.
Since condensate must be “lifted” to an elevation, it adds additional back-pressure to the discharge (outlet) side of the trap.
For this example the condensate return line pressure is 5 psig. We first need to calculate Lift Height Pressure :