A piston suction pump with its cylinder above ground lifts water from a well no deeper than about 7 m to the water, because it works by lowering the pressure in the pipe so that the atmosphere pushes water up, and the atmosphere supports a column of only 10.3 m at sea level. Within that limit it delivers 15-20 L/min, needs an airtight suction pipe and a foot valve, and must be primed with water before it will lift.
Part of Deep Wells
A suction hand pump is a piston pump whose cylinder sits at the top of the well. The piston draws water up a pipe from below; the pump body and its leather seals are above ground where they can be reached and repaired.
The Atmosphere Does The Lifting, And It Has A Limit
When the piston rises, the pressure in the suction pipe drops. The air around the well pushes down on the water surface, and that pressure pushes water up the pipe into the low-pressure space. The tallest column of water that the atmosphere can support is
h = p ÷ (ρ × g) = 101,325 Pa ÷ (1,000 kg/m³ × 9.81 m/s²) = 10.33 m, about 10.3 m
at sea level. No pump design can beat that for suction. Leaks past the valves and seals, friction in the pipe, and the water’s own tendency to boil at low pressure reduce what a real hand pump manages to about 6-7 m (Hand Pump gives the same limit for a cistern, with the altitude effect). The Deep Wells guide sets the practical maximum at 7 m. If the dry-season water is deeper than that, the cylinder must go down in the well: see Deep-Well Pumps.
What One Stroke And One Pull Cost
Output. The water drawn per stroke is the cylinder volume. Take a cylinder bore of 80 mm (within the 75-100 mm of Hand Pumps) and an assumed stroke of 200 mm: π ÷ 4 × 0.08² × 0.2 = 1.0×10⁻³ m³ = 1.0 L. At 20 strokes a minute that is 20 L/min with perfect seals, in line with the 15-20 L/min the Deep Wells guide gives once leaks are taken into account.
Force. At a lift of 6 m the pressure difference across the piston is 1,000 × 9.81 × 6 = 58,860 Pa. The piston area is π ÷ 4 × 0.08² = 5.03×10⁻³ m². The force on the rod is 58,860 × 5.03×10⁻³ = 296 N, about the weight of a 30 kg mass. The pump handle is a lever with a ratio of 3:1 or 4:1, so the hand pushes with 296 ÷ 3 = 99 N or 296 ÷ 4 = 74 N, plus the weight and friction of the piston and rod. That is comfortable for one person; the effort grows in direct proportion to the lift.
What You Need
- A pump — built following Pump Construction or Hand Pumps: cylinder, piston with leather cup, two check valves, rod, lever
- A suction pipe — airtight, the shortest run, with no high points
- A foot valve and strainer — at the bottom of the pipe, below the lowest water level
- A sealed pump base on the well cover or apron
- Water for priming
Method: Fit, Seal, Prime, Test
Step 1: Measure the dry-season depth from the pump to the water. It must be under about 7 m.
Step 2: Fit the suction pipe airtight, with the foot valve and strainer at least 0.3 m under the lowest expected water level. Check every joint; a single air leak stops the pump lifting.
Step 3: Seal the pump to the well cover so nothing can enter between the two.
Step 4: Prime. Pour clean water into the cylinder until it is full; it wets the leather seal and lets the piston make a vacuum. Pump; it may take 10-15 strokes to draw the water up, and if it has not lifted after 20 strokes, look for an air leak.
Step 5: Test the flow. Time a 20 L bucket; compare with the table in Pump Selection.
Step 6: Protect against frost. Water left in the above-ground cylinder freezes and can crack it; drain it or insulate it in freezing weather.
Common Mistakes
- A well deeper than the limit. The pump never lifts.
- Air leaks in the suction pipe. The most common fault; test by pouring water over the joints while pumping, or by filling the pipe and watching for loss.
- Dry leather. A dried cup leaks; keep the cylinder wet and the leather oiled.
- No cover. The pump base must seal the well.
Safety
Levers and crushed fingers
The handle and rod can trap fingers at the pivot and the stuffing box. Keep children away from the handle, and block it when the pump is being repaired. Priming water must be clean: pouring a bucket of untreated water down a well to start a pump contaminates it.
What’s Next
- Learn next: Deep-Well Pumps — when the water is deeper than 7 m
- Combine with: Well Protection — sealing the wellhead around the pump