Suction Line Velocity


Suction Line Velocity Calculator



GPM / 2.45 X Diameter squared = ft/sec velocity

Sizing a Suction Line

When a centrifugal pump is operating it creates a vacuum in the suction line. The vacuum draws water up to the pump like a drink straw. This rate of draw creates a water velocity up the suction line not to exceed 7 ft/sec. If the velocity is too fast over 7 feet per second the vacuum will vacuum air out of the water. It will physically pull O^2 out of the H2O. The air will knock around and create a loud cavatation knocking sound, that will damage the pump. To eliminate cavatation simply increase the size or diameter of the suction line to slow the water’s velocity. A lower or slower velocity will also allow the pump to operate more efficiently. Correctly sized suction lines create slower less turbulent water and will increase pressure (psi) and volume (GPM) at the same horse power and torque.