Every few months someone asks for a surface pump that can pull water from a well 15 metres deep. The answer is always the same: no pump on earth can do that by suction, and the reason is the sky.
Suction is a push, not a pull
A surface pump does not actually pull water. It creates a low-pressure zone, and the weight of the atmosphere on the water surface pushes water up the pipe. At sea level, the atmosphere pushes with about 10.3 metres of water column, roughly 1 bar. That is the theoretical maximum, and it exists only in a perfect vacuum with perfect pipes.
Real pumps leak a little, pipes restrict flow, and water starts to cavitate before the theoretical limit. Subtract elevation, friction and the pump's own NPSH requirement, and the practical ceiling lands around 7 to 8 metres. At altitude it is lower still.
What to do below 8 metres
- Move the pump down. Sometimes a lower platform or a pit solves it cheaply.
- Use a deep-well injector on a jet pump, which trades efficiency for reach up to roughly 25 metres.
- Go submersible. Below 8 metres this is usually the honest answer. Pushing water up has no atmospheric limit; only the pump's head rating matters.
If your water level is anywhere near 8 metres, do not design at the limit. Suction lift ratings assume ideal conditions that exist in test labs, not in wells with a summer drawdown.