Net positive suction head (NPSH)

The net positive suction head available (NPSHA) is the NPSH in feet available at the centerline of the pump inlet flange. The net positive suction head required (NPSHR) refers to the NPSH specified by a pump manufacturer for proper pump operation.


Source: Handbook of water and wastewater treatment plant operations

Wikipedia:  https://en.wikipedia.org/wiki/Net_positive_suction_head