📖 How To Use
How to Use This Pump Head Calculator
Sizing a pump correctly prevents under-powered systems and wasted energy. Follow these steps:
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Enter static head
Measure the vertical height from the water source surface to the highest discharge point. This is the dominant factor in most residential and agricultural pump systems. Use metres or feet.
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Enter total pipe length
Add the suction pipe length (pump to water source) and discharge pipe length (pump to delivery point). For a straight run, this is straightforward — for complex routes, add each segment.
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Set pipe diameter and material
Internal pipe diameter directly affects velocity and friction loss. Select your pipe material — PVC has the lowest friction (C=150), old steel or concrete the highest (C=100).
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Set required flow rate
Enter the volume of water your system needs per hour. Household use: typically 500–1,500 L/h. Agricultural drip systems: varies widely by crop and field size.
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Set minor losses percentage
Minor losses account for bends, valves, tees, and fittings. A typical allowance is 10–20% of friction head. Complex systems with many fittings can reach 30%.
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Read your results
Total Dynamic Head (TDH) is the figure you give to a pump supplier. The calculator also shows pressure in PSI, bar, and kPa for pump spec sheets that use those units.
Pro tip: Always add a safety margin of 10–15% to your calculated TDH when selecting a pump. This covers ageing pipes, future expansion, and any measurement uncertainties. A pump working at 80–85% of its curve also runs more efficiently than one at full load.
📐 The Formula
Pump Head Pressure Formula Explained
Total Dynamic Head (TDH) is the sum of three components — static head, pipe friction loss, and minor losses:
TDH = H_static + H_friction + H_minor
H_static = vertical elevation difference (m)
H_friction = pipe friction head loss (Hazen-Williams)
H_minor = H_friction × (minor_loss_% ÷ 100)
Hazen-Williams Friction Loss Formula
This calculator uses the Hazen-Williams equation, the industry standard for water distribution in pipes with turbulent flow:
H_f = (10.67 × L × Q^1.852) ÷ (C^1.852 × D^4.87)
L = pipe length (m)
Q = flow rate (m³/s)
C = Hazen-Williams roughness coefficient
D = internal pipe diameter (m)
Pressure Conversions from TDH
Pressure (kPa) = TDH (m) × 9.807
Pressure (bar) = TDH (m) × 0.09807
Pressure (PSI) = TDH (m) × 1.4223
Hazen-Williams C Coefficient by Pipe Material
| Pipe Material | C Value | Friction Level | Typical Use |
|---|
| PVC / Plastic | 150 | Lowest | Modern residential & agricultural |
| HDPE | 140 | Very Low | Buried mains, irrigation |
| New Steel | 130 | Low | Commercial, industrial |
| Galvanised Steel | 120 | Moderate | Older residential, light industrial |
| Cast Iron (new) | 130 | Low–Moderate | Municipal mains |
| Cast Iron (old) | 100 | High | Aged mains >20 years |
| Concrete | 100–110 | High | Large diameter mains |
Typical Pump Head Reference
| Application | Static Head | Typical TDH | Pressure |
|---|
| Rooftop tank (2 storeys) | 6–8 m | 10–15 m | 1.0–1.5 bar |
| Rooftop tank (5 storeys) | 15–18 m | 22–28 m | 2.2–2.7 bar |
| Irrigation (100 m run) | 2–5 m | 8–18 m | 0.8–1.8 bar |
| Borehole pump (30 m depth) | 30–35 m | 40–50 m | 3.9–4.9 bar |
| Fire suppression system | 20–30 m | 50–80 m | 4.9–7.8 bar |
🎯 Use Cases
When to Use a Pump Head Calculator
🏠
Residential Water Supply
Sizing a booster pump to raise pressure from a ground-level tank to upper floors or a rooftop tank.
🌱
Agricultural Irrigation
Calculating pump requirements for drip or sprinkler systems across fields with varying elevation.
🏗️
Commercial & Industrial
Designing water distribution for multi-storey buildings, factories, or processing plants.
⛏️
Borehole & Well Pumps
Determining submersible pump specifications based on well depth and required delivery head.
This pump head pressure calculator is most accurate for clean fresh water at normal temperatures (10–25°C). For viscous fluids, hot water systems, or very high-flow turbulent conditions, consult a hydraulic engineer for additional correction factors.
❓ FAQ
Frequently Asked Questions
What is total dynamic head (TDH) and why does it matter?
Total Dynamic Head (TDH) is the total equivalent height that a pump must lift water against, accounting for actual vertical elevation plus all friction losses in the pipes and fittings. It is the single most important number for pump selection — a pump's performance curve plots flow rate against head, and your operating point must fall on that curve. Undersizing TDH leads to insufficient flow; oversizing wastes energy and can cause excessive system pressure.
How do I calculate pump head pressure manually?
To calculate pump head manually: (1) measure the static head — the vertical height from water source to discharge; (2) calculate pipe friction loss using the Hazen-Williams formula H_f = (10.67 × L × Q^1.852) ÷ (C^1.852 × D^4.87); (3) add minor losses — typically 10–20% of friction head for bends and fittings; (4) sum all three: TDH = Static Head + Friction Loss + Minor Losses. This calculator does all that automatically.
What is the difference between static head and total dynamic head?
Static head is just the vertical elevation difference between the water source and the delivery point — a fixed physical measurement. Total dynamic head (TDH) is static head plus all the additional pressure loss caused by water flowing through pipes, bends, valves, and fittings. TDH is always larger than static head, often by 20–50% depending on pipe length, diameter, and flow rate.
How do I convert pump head (metres) to pressure (PSI or bar)?
To convert pump head in metres to pressure: multiply by 0.09807 to get bar, or multiply by 1.4223 to get PSI, or multiply by 9.807 to get kPa. For example, 20 m TDH = 1.96 bar = 28.4 PSI = 196 kPa. These conversions assume fresh water at standard gravity (9.807 m/s²).
What percentage should I use for minor losses?
Minor losses (from bends, elbows, tees, valves, and entry/exit losses) are typically expressed as a percentage of the friction head loss. Use 10% for simple systems with very few fittings, 15–20% for standard residential or irrigation systems, and 25–30% for complex systems with many bends, gate valves, check valves, and reducers. When in doubt, use 20% — it is the most common industry default.
Why does pipe diameter affect pump head so dramatically?
Pipe diameter has an outsized effect because friction loss is inversely proportional to diameter raised to the power of 4.87 in the Hazen-Williams equation. Halving the pipe diameter increases friction loss by a factor of roughly 28 at the same flow rate. This is why upgrading from a 25 mm to a 32 mm pipe can dramatically reduce the pump head required — and potentially allow a smaller, cheaper pump to do the same job.
What pump head do I need for a rooftop water tank?
For a typical two-storey home with a rooftop tank 6–8 metres above the pump, and 20–30 metres of pipe, you typically need a TDH of 12–20 metres (1.2–2.0 bar / 17–29 PSI). For a five-storey building, expect 25–35 metres TDH. Always add 10–15% safety margin and select a pump whose performance curve crosses your operating point at 70–85% of its maximum flow — this keeps the pump in its most efficient range.
Can I use this calculator for submersible borehole pumps?
Yes. For a submersible borehole pump, the static head is the total vertical lift from the pumping water level (the water level when the pump is running, not the static water level) to the discharge point. Enter the well depth to pump level as static head, then add the above-ground delivery height. The friction loss calculation works the same way for the discharge pipe. Many borehole applications result in total TDH of 40–80 metres.