Enter the flow, the pipe and the height the liquid has to be lifted. The calculator adds static head, pressure head and friction loss to the total dynamic head (TDH) you need from the pump.
Total dynamic head
Friction head
Velocity in pipe
Pump pressure rise
Hydraulic power
How total dynamic head is calculated
A pump has to lift the liquid, overcome any pressure difference and push it through the pipe against friction. Added together this is the total dynamic head (TDH), the point you look up on the pump curve:
H = z + Δp ÷ (ρ · g) + hf
hf = f · (L ÷ D) · v² ÷ (2g)
z
static head: height from source liquid level to outlet
Δp
extra pressure needed at the outlet
hf
friction head in the pipe (Darcy-Weisbach)
f
friction factor from the Swamee-Jain equation
L, D
pipe length and inside diameter
v
flow velocity in the pipe
Worked example
A pump moves 20 m³/h of water through 100 m of 50 mm steel pipe to a tank 15 m higher. The velocity is 2.83 m/s and the friction factor 0.021, so the friction head is 0.0213 × (100 ÷ 0.05) × 2.83² ÷ 19.6 = 17.4 m. Total head is 15 + 17.4 = 32.4 m. A 65 mm pipe would cut the friction to about 4.6 m and the total to under 20 m.
Total dynamic head = static head + pressure head + friction head. Static head is the vertical lift. Pressure head converts any pressure difference into height (1 bar = 10.2 m of water, 1 psi = 2.31 ft). Friction head is the loss in pipes and fittings, here from the Darcy-Weisbach equation.
How do I convert pump head to pressure?
Pressure (bar) = head (m) × specific gravity ÷ 10.2. In US units, psi = head (ft) × specific gravity ÷ 2.31. A pump giving 30 m of head raises water pressure by about 2.9 bar.
What is a good velocity in a pump pipe?
Discharge lines are usually sized for 1.5 to 3 m/s (5 to 10 ft/s), suction lines for 0.6 to 1.5 m/s (2 to 5 ft/s). Higher velocity means more friction, noise and wear.
Is the head the same for water and other liquids?
A pump develops the same head in meters regardless of the liquid, but the pressure and power scale with the specific gravity. Viscous liquids such as oils have much higher friction than this calculator assumes.