Quick answer: Total dynamic head (TDH) — the total head a pump must generate — is the sum of four parts: TDH = Static head + Friction head loss + Pressure head + Velocity head. Static head is the vertical lift; friction head is the loss in pipes and fittings; pressure head is any required delivery pressure; velocity head is usually small. The answer is expressed in metres (or feet) of water.
What is pump head?
Pump head is the height to which a pump can raise water, expressed in metres. It is a more useful design quantity than pressure because it is independent of the fluid's density. To select a pump you match its head–flow curve to the system's total dynamic head at the required flow rate.
The total dynamic head formula
TDH = H(static) + H(friction) + H(pressure) + H(velocity)
H(static) = vertical distance from source level to discharge level
H(friction) = losses in pipe + fittings (Hazen-Williams or Darcy-Weisbach)
H(pressure) = required residual pressure at outlet, converted to head
H(velocity) = v² / 2g (often negligible)Friction loss by the Hazen-Williams method: h = 10.67 × L × Q^1.852 / (C^1.852 × d^4.87), where L is length (m), Q is flow (m³/s), C is the pipe roughness coefficient and d is the internal diameter (m).
How to calculate pump head — step by step
- Static head: measure the vertical rise from the water source to the highest discharge point.
- Friction head: calculate pipe friction for the total pipe length, then add fitting losses (use equivalent lengths for elbows, valves, tees).
- Pressure head: convert any required outlet pressure to metres (1 bar ≈ 10.2 m of water).
- Velocity head: add v²/2g if significant.
- Sum them for TDH, then select a pump whose curve delivers that head at your design flow.
Hazen-Williams C values
| Pipe material | C coefficient |
|---|---|
| PVC / plastic | 150 |
| Copper | 140 |
| New cast iron | 130 |
| Galvanised steel | 120 |
| Old / corroded steel | 100 |
Enter static lift, pipe length, diameter, flow and fittings — get total dynamic head and the pump duty point in seconds.
Open the Pump Head Calculator →Worked example
Pumping water 20 m up through 60 m of 50 mm PVC pipe at 5 m³/hr, with 8 m of friction loss in pipe and fittings and a required outlet pressure of 1 bar:
- Static head = 20 m
- Friction head ≈ 8 m
- Pressure head = 1 bar ≈ 10.2 m
- Velocity head ≈ negligible
TDH = 20 + 8 + 10.2 ≈ 38.2 m. Select a pump that delivers ≥38 m of head at 5 m³/hr, with a small margin.
Tips for accurate results
- Do not forget fitting losses — elbows and valves can add several metres of equivalent length.
- Keep pipe velocity around 1–2 m/s to balance friction loss against pipe cost.
- Add a modest safety margin, but avoid gross oversizing (it pushes the pump off its best-efficiency point).
Related MEP calculators
Size the storage side with the Water Storage Tank Calculator and the Fire Water Tank Calculator.
Frequently Asked Questions
What is total dynamic head (TDH)?
TDH is the total head a pump must generate, equal to static head plus friction head plus pressure head plus velocity head, expressed in metres or feet of water.
What is the difference between static and dynamic head?
Static head is the vertical lift with no flow. Dynamic head adds the friction and velocity losses that occur when water is actually moving through the pipes and fittings.
How do you convert pressure to head?
For water, 1 bar is about 10.2 metres of head, and 1 psi is about 0.703 metres. Divide pressure by the fluid specific weight to convert precisely.
Why is fitting loss important in pump head?
Elbows, valves and tees add significant equivalent pipe length. Ignoring them underestimates friction head and can leave the pump undersized.