What is suction lift and why does it matter for pump selection?

• A. The vertical distance water is lifted into the pump; higher suction lift requires higher NPSH and can reduce pump efficiency.
• B. The horizontal distance from water source to pump.
• C. The amount of air in the irrigation lines.
• D. Higher suction lift increases discharge capacity.

Answer: (A)

Suction lift is the vertical distance the water must be raised into the pump from the source. The higher this lift, the more hydrostatic head the pump has to overcome just to pull water into the impeller, which causes the pressure at the suction side to drop. That lower suction pressure means the pump must have more available Net Positive Suction Head (NPSH) to avoid cavitation. If the available NPSH is not enough, cavitation can occur, leading to noise, wear, reduced flow, and lower efficiency. Because of this, suction lift matters for pump selection: you need a pump with a sufficient NPSHR for the site conditions, or you must reduce the lift or suction-line losses (for example, by shortening the suction distance, increasing pipe diameter, or reducing fittings and friction).