Choose a pump by two figures, not by horsepower: the flow rate you need (m³/h) and the total head it must overcome (meters). Get these right and match the pump type, and you avoid the two common mistakes. One is a pump that moves plenty of water but cannot lift it high enough. The other is a pump far larger than the job needs.
The two figures that matter
Flow rate (Q)
The volume of water moved per unit of time, in m³/h or L/s. Your task sets it: irrigating a given area, draining a pit by a deadline, or filling a tank in an hour.
Total head (H)
The total resistance the pump must work against, expressed in meters. It is the sum of three parts:
- Static head: the vertical lift from the water source to the discharge point.
- Friction loss: the resistance inside the pipe and fittings. Longer pipe runs and smaller diameters add a lot of friction.
- Pressure head: any pressure required at the outlet, for example for sprinklers or a nozzle.
The sum of the three is the head your pump must deliver at your required flow.
Check the suction lift
Atmospheric pressure limits how high a pump can draw water up to itself. In practice the limit is about 7–8 m at sea level, and less at altitude. A highland site loses roughly a meter of usable suction for every 1,000 m of elevation, which is why a pump that worked at the coast can fail after a move to a high site. Engineers check this condition as NPSH, the net positive suction head available at the pump inlet. If the pump sits well above the water surface, choose a self-priming pump or fit a foot valve. Keep the suction pipe short and wide to reduce losses.
Match the pump type to the job
| Pump type | Best for |
|---|---|
| Standard centrifugal | High flow, low to moderate head: irrigation, water transfer, drainage |
| High-pressure / multistage | Moderate flow, high head: tall lifts, long-distance delivery, sprinklers or pressure boosting |
HTX offers both standard and high-pressure diesel water pumps; compare them in the water pump catalog. Which family is right depends on whether flow or head dominates your job.
Diesel or electric drive
A diesel pump suits off-grid, remote or portable work, and any site where grid power is unreliable. This is common in agriculture, construction and mining. Choose electric drive only where stable mains power is already available.
A diesel pump is driven by a diesel engine, so it needs the same oil and filter service as any other engine. It also loses output at altitude: the derating rules in our altitude derating guide apply to the engine that drives your pump.
Worked example
A farm irrigates a field from a river. The field inlet is 12 m above the river. The pipe run is 150 m of mid-size pipe, which adds roughly 4–6 m of friction at the target flow. The sprinklers need about 15 m of pressure head.
- Total head H ≈ 12 + 5 + 15 = ~32 m at the required flow.
- The right machine is a standard centrifugal pump that delivers your Q at 32 m, with the duty point near the middle of its curve rather than at the far right end.
- If the lift were 40 m and the line 500 m, head would dominate the choice. That calls for a high-pressure pump.
A five-step method
- Find the required flow (Q) from the task.
- Add up the total head (H): static lift + friction loss + outlet pressure.
- Read the pump curve. The pump must deliver Q at H, its duty point. That point should sit near the best-efficiency point (BEP), not at the far end of the curve.
- Add a margin for pipe ageing and future demand.
- Check the suction lift and pipe diameter. An undersized pipe cuts the available head, so do not reduce the diameter to save cost.
The most expensive mistakes
- Buying by horsepower. Two pumps with the same engine can have completely different curves.
- Ignoring friction. A long, thin delivery line can use up more head than the vertical lift itself.
- Suction lift at altitude. The 7–8 m limit at sea level gets smaller as elevation rises. Plan the pump position for it.
- Running at the end of the curve. A pump that runs far from its BEP wears quickly and delivers less.
Send us your flow, your lift and a rough pipe layout, and our team will recommend the right HTX pump and drive. Request a quote or message us on WhatsApp. We reply within 24 business hours.