Pump Head Pressure

Overview

Engineering reference data for Pump Head Pressure in fluid mechanics.

Key Formulas

Reynolds Number

$Re = \frac{\rho v D}{\mu}$

Ratio of inertial to viscous forces — determines flow regime.

Bernoulli's Equation

$P + \frac{1}{2}\rho v^2 + \rho g h = \text{const}$

Conservation of energy for steady, inviscid, incompressible flow.

Continuity Equation

$A_1 v_1 = A_2 v_2$

Conservation of mass for incompressible flow.

Darcy-Weisbach

$\Delta P = f \frac{L}{D} \frac{\rho v^2}{2}$

Pressure drop due to friction in a pipe.

Variables

Symbol	Description	Unit
$Re$	Reynolds number	—
$\rho$	Fluid density	kg/m³
$v$	Flow velocity	m/s
$D$	Characteristic dimension	m
$\mu$	Dynamic viscosity	Pa·s
$P$	Pressure	Pa
$f$	Darcy friction factor	—

Head vs. Pressure Data Table

For water (SG = 1.0 at 62°F / 17°C), the relationship between pump head in feet and pressure in psi is provided below.

Head and Pressure for Different Liquids

The pressure developed by a pump depends on the fluid's specific gravity (SG), even if the developed head (ft) is identical. The following table illustrates this for a head of 100 ft.

Key Insight: Head vs. Pressure

Identical pumps running at the same speed will develop the same head regardless of the fluid being pumped. However, the discharge pressure will vary significantly because pressure is a function of both the head and the fluid's density (specific gravity). This is why pump performance curves are typically plotted in terms of head (feet or meters) rather than pressure (psi or bar). Using head makes the curve universally applicable to any fluid, simplifying system design and pump selection.

Interactive Charts

References

• Original Source