ocean runner return pump head loss?

[gerry45]

I have a submersible ocean runner 2500 for a return from my sump.
It is supposed to be 700gph at 0 head. sure seems lower than that.
head is approx 4 feet.

 

[sign guy]

find out fast first you will need a hour and 700 milk jugs

most pumps will lose up to 100gph with a 4 ft head