This displacement view of a bucket lift pump pairs its swept volume with the two-valve cycle: foot-valve filling on the upstroke and piston-valve transfer on the downstroke.
Lift Pump (form 1) Interactive Calculator
Estimate swept volume, delivered flow after a declared volumetric efficiency and the static suction pressure drop. No arbitrary universal suction-lift limit is assumed.
Equation Used
- Water density is 1000 kg/m3 and g is 9.81 m/s2.
- Bore and stroke describe the ideal swept cylinder volume.
- Pipe losses, acceleration head, leakage variation and cavitation margin are excluded.
Bore and stroke set swept volume; cycle rate and entered volumetric efficiency set estimated flow. Static suction pressure drop depends on the entered water-column height.
Displacement through a valved piston
During the upstroke, the foot valve opens and the piston valve closes; new water fills the swept space below while water above the piston rises toward the outlet. During the downstroke, the foot valve closes and the piston valve opens so water transfers through the piston.
Comparing bucket-pump displacement
Use this model to compare the water volume swept by different cylinder bores and strokes. The flow calculation then applies your chosen cycle rate and volumetric efficiency.
The animated bucket pump has a valve through its piston and a foot valve below it. The drawing explains that cycle rather than selecting a commercial pump, installation depth or operating speed.
Swept volume and delivered flow
The static suction-column pressure drop is rho gh. This does not create a universal seven-metre limit; available atmospheric pressure, vapor pressure, dynamic losses and required margin must be assessed separately.
Worked example: 90 mm bore and 150 mm stroke
Enter a 90 mm bore, 150 mm stroke, 40 complete cycles/min, volumetric efficiency of 0.85 and 4 m suction lift.
Swept volume is π(0.090)² × 0.150 / 4 = 0.0009543 m³, or 0.9543 L per cycle. Estimated delivery is 0.9543 × 40 × 0.85 = 32.44 L/min, equivalent to 0.0005408 m³/s.
Static suction pressure drop is 1000 × 9.81 × 4 = 39,240 Pa, or 39.24 kPa. This does not include pipe or valve losses.
Holding the efficiency assumption fixed, 20 cycles/min gives 16.22 L/min and 60 cycles/min gives 48.67 L/min. Those are arithmetic comparisons, not claims about comfortable hand cadence or actual valve performance.
How geometry and rate change the results
| Change | Calculated effect |
|---|---|
| Double bore diameter | Four times swept volume and flow, with stroke, rate and efficiency fixed. |
| Double stroke | Twice swept volume and flow. |
| Double cycle rate | Twice flow if the entered efficiency remains unchanged. |
| Increase suction lift | Greater static suction pressure drop; this model does not automatically alter flow. |
Actual delivery depends on inlet conditions, valve behavior and leakage as well as displacement. Maximum suction lift, operator effort, service life and component sizing require information beyond these inputs.
Bucket-pump calculation questions
Why does suction lift not change the calculated flow?
Flow is calculated from swept volume, cycle rate and the efficiency you enter. The model does not calculate how valve behavior or leakage changes with lift.
Does the static pressure drop give the maximum lift?
No. It is the pressure associated with the entered water column. Available atmospheric pressure, water vapor pressure, losses and cavitation margin must be assessed separately.
How should I choose volumetric efficiency?
Use a value supported by the pump’s data or measurements under the relevant conditions. The calculator treats it as an input rather than predicting it.
Does increasing bore make the pump easier to operate?
A larger bore displaces more water per cycle but also changes the drive load. This calculator does not calculate hand force or an operator’s sustainable work rate.
Is the animation a construction drawing?
No. It illustrates the piston and foot valves and the entered swept geometry. Valve profiles, seal fits, materials and structural ratings are not specified.
Can the result diagnose a flow shortfall?
No. Many operating and mechanical conditions can reduce measured delivery. The calculated flow provides a comparison, not a diagnosis or a repair instruction.
Mechanism reference
- FAO, Water Lifting Devices: describes the bucket-pump valve cycle and the piston-pump discharge relationship.
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