This bucket-type lift pump has two checks: a foot valve at the inlet and a valve through the piston. Their alternating states let the downstroke transfer water above the piston and the upstroke lift that water toward the outlet.
Lift Pump Interactive Calculator
Compare suction lift with an ideal atmospheric-pressure head budget. The pressure budget gives an ideal comparison with the entered lift; it does not establish an installation limit.
Equation Used
- Water density is 1000 kg/m3 and g is 9.81 m/s2.
- Atmospheric and vapor pressures are absolute pressures.
- Entered suction loss is expressed as metres of water head.
Atmospheric pressure, water vapor pressure and suction losses determine the available head in this ideal comparison. Greater hand force does not increase the atmospheric-pressure budget.
Bucket-pump valve sequence
On the upstroke, the piston valve is closed and the foot valve opens. Water enters below the rising piston while the water already above it is lifted toward the spout. On the downstroke, the foot valve closes and the piston valve opens, allowing water to pass through the descending piston.
Comparing a pump’s suction conditions
Use the pressure-budget calculation to explore how atmospheric pressure, water vapor pressure and suction-side losses affect available head. Enter the vertical lift between the source water level and the pump inlet.
The bucket-pump diagram explains the alternating foot and piston valves. It does not specify a particular well installation, flow rate, seal material or pump rating.
Ideal suction-head budget
The displayed margin subtracts static suction lift from this ideal budget. Hand or lever force does not create additional suction head. Real installations require transient-loss analysis and a positive cavitation margin.
Worked example: 5 m suction lift
Enter 101.325 kPa absolute atmospheric pressure, 2.34 kPa absolute water vapor pressure, 1.0 m suction-loss allowance and 5.0 m static suction lift.
The ideal available head is (101.325 − 2.34) × 1000 / (1000 × 9.81) − 1.0 = 9.09 m. Subtracting the 5.0 m lift leaves an ideal head margin of 4.09 m. Static pressure drop is 1000 × 9.81 × 5.0 / 1000 = 49.05 kPa.
That lift uses approximately 55.0% of the calculated budget. A positive result does not establish satisfactory operation: transient acceleration head and the required cavitation margin are not included.
How the inputs affect the head budget
| Input change | Effect in this calculation |
|---|---|
| Lower atmospheric pressure | Reduces ideal available head. |
| Higher water vapor pressure | Reduces ideal available head. |
| Greater suction-loss allowance | Reduces available head metre for metre. |
| Greater static lift | Consumes more of the available head and reduces the margin. |
The model does not compare pump purchase prices, service intervals or flow capacities. It also does not establish the maximum depth of a well: the cylinder’s position relative to the water level matters.
Lift-pump questions
Does a positive margin guarantee the pump will work?
No. It only means the entered lift is below this ideal pressure budget. The calculation omits transient acceleration head and the required cavitation margin.
Why must pressure be absolute?
The available-head equation uses the difference between atmospheric pressure and water vapor pressure. Both must use the same absolute-pressure reference.
Does this calculator predict flow?
No. It compares suction head. Flow also depends on bore, stroke, cycle rate, leakage and valve behavior, none of which are inputs here.
Does more handle force increase the maximum suction head?
No. Handle effort moves the piston, but it does not increase the atmospheric pressure acting on the source water.
Is well depth the same as suction lift?
No. Suction lift is the vertical distance between the relevant source water level and pump inlet. A cylinder located farther down a well has a different suction lift than one at the surface.
Can a negative result still be shown in the animation?
Yes. The valve sequence remains visible to explain the mechanism, while the result states that the entered lift exceeds the ideal available head. The animation is not a claim that water would be delivered under those conditions.
Mechanism reference
- FAO, Water Lifting Devices: describes the bucket-pump piston valve, foot valve and alternating upstroke/downstroke flow.
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