Suction lift refers to the pressure (negative pressure) on the suction side of the pump.
The pressure can be measured from the centre line of the hydraulic part of the pump down to the water surface on the suction side of the pump.
In theory, it should be possible to suck water from a depth of 10.33 metres, however, this would require an absolute vacuum. In practice, the maximum is therefore much lower.
To avoid cavitations (the phenomenon of formation of vapour bubbles of a flowing liquid in a region, where the pressure of the liquid falls below its vapour pressure) it is important to compare the required NPSH (Net Positive Suction Head) to the available NPSH.