Hose Selection Flow Capacity Nomograph Flow Capacities of Caterpillar Hose at Recommended Flow Velocities The chart below is designed and provided as an aid in the determination of the correct hose size. 1. determine flow and velocity of system; 2. find them on indexes below; 3. connect line with straight edge to determine correct hose size. AREA (IN 2 ) = FLOW (GPM) X .3208 VELOCITY (FT/SEC) Recommended Maximum Velocity for Suction Lines Inside Diameter of Hose, Inches Flow, Gallons per Minute (gpm) Velocity, Feet Per Second Recommended Maximum Velocity for Pressure Lines 5