Allenair drum pumps are designed around our tandem cylinder design joining two cylinders togeth-
er with a common head and rod. The total pump unit®is divided into two sections; the drive section
and the pump section. By utilizing our Valve-In-Head cylinder as the air motor, the rod and pump
piston will move in unison, creating suction on the lower half of the piston and pressure on the up- per half. On the down stroke the check piston moves freely through the fluid in the dip tube.