The Wilden Pump is an air operated , positive displacemnt, self-priming pump. This drawing show the flow pattern through the pump upon its initial stroke.It is assumed the pump has not been primed prior to its initial stroke. Applications Self-Priming Application Pumps range in suction lift capability from 4 - 21 feet dry(1.37-6.4 meters).25 feet97.62 meters)can be reached in a primed condition.Suction lift will vary according to materials of construction and application parameters.All data is based on pumping water at 68'F(20"C) Submerged Application All pumps are completley submersible.Air exhaust must be plumbed above liquid level & materials of construction must be compatible with surrounding liquid. Positive Suction Head Application Used extensively for drawing off the bottom of holding tanks, clarifiers, etc.Pumps operate most effiently when inlet pressure is limited to 7-10 psi (.48-.68 bar). Visit the Wilden website @ www.wildenpump.com For more info please fill out the Form and we will get back to you A.S.A.P