Head in feet vs psi

Both units are commonly used to quantify the outlet pressure of a pump.
Other units are also used: water column(WC), Pascal(Pa), bar, atmosphere(atm), torr.

1 psi = 2.31 (or 2.3066587368787 to be more precise) head in feet (of water)

This value is essential when selecting a pump, it indicates if the pump can supply the required pressure. There are many opposing parameters to the fluids movement such as: the product’s viscosity, head loss through pipe, gravity…
For any given pump, the performance curve is always given considering the pumped liquid is water, density :1.00 @ 3.98°C and Patm.