Irrigation Pumps

The two numbers: flow and head

Flow is the volume the system must deliver — set by the drip lines, emitter count and run time, worked out in the design. In practical terms it's the flow of the zone(s) the pump serves, typically a fraction of the whole field per run. Head is the total pressure the pump must generate: the static lift (the height from the water source's level to the field, in metres — 10 m of lift ≈ 1 bar), plus the friction loss through the pipes over their lengths, plus the working pressure the emitters need at the farthest, highest point.

Both numbers come from your farm's actual geometry and layout — which is why "a pump for one acre" from a shop is a coin flip, and why the pump is always specified from the design, not chosen first. A pump that's too small starves the far end; one that's far too big hammers pressure into a system built for half of it (the classic burst-line scenario, fixed by a regulator or a better pump choice).

Power options in Kenya

Solar sizing is its own calculation (array size vs pump draw vs daily irrigation hours vs season sun) — do it once and the pump runs for a decade on sunshine. Where a farm has a gravity option instead, the pump question disappears entirely, which is the cheapest pump there is.

Pump types you'll meet

• End-suction centrifugal — the workhorse for surface water (dam, river, tank intakes); handles the volumes small and medium farms need.
• Submersible — lowered into a borehole; the standard borehole pump, sized to the borehole's yield and depth.
• Jet/booster — low-head top-ups and tank filling; the small end of the scale.
• Multi-stage / high-head — deep boreholes and significant lifts; where the head number gets big.

The type follows the source and the lift; the size follows flow × head. Both in the design.

Source matching

• Borehole: the pump must not pull harder than the borehole can give — over-pumping a shallow-yield borehole drops the water level and, seasonally, dries it. The design checks the yield against the demand, and the water assessment covers the quality side (iron, sand).
• Dam/river: an intake strainer before the pump, and the wet-test condition (lowest season water level, not the full level) is what the head is calculated from.
• Tank: the tank's height is the head; the pump (if any) tops up the tank, and the system may run gravitationally from it — the smallholder classic.

Maintenance notes

• Run pumps above their minimum flow and they survive; run them dry (an empty tank, a dropped water level) and seals die — an empty-tank protection or level switch is cheap insurance.
• Seasonal service: check seals, bearings and the intake strainer at start-up; the start-of-season pump failure is almost always something that showed a warning in the previous season.
• Solar: keep the array clean (dust is the silent production killer) and the connections dry. The maintenance service covers all of it on a calendar.

Choosing a pump

Sequence: source → static lift → system flow (from the design) → friction (from the pipe routing) → working pressure → power option from the farm's economics. Then the pump that meets those numbers, not the one with the biggest brand on the crate. For your farm's specification: request a quote — the pump is the line item we'll justify in writing, with the numbers behind it.