A · Suction depth — How far the water is below the pump.

B · Delivery height — How far up the water must be pushed (to the top water level of the tank, including any stand).

C · Pipe distance — The real length of pipe from pump to tank (walk the actual route).

Total Head = Suction + Delivery height + Friction loss in pipes + Desired pressure at the end. This is the single number the pump must overcome.

Rule: suction pipe should be one size larger than delivery pipe. Never reduce pipe size right at the pump outlet.

1 person ≈ 100–150 L/day
Average home (5 people) ≈ 500–800 L/day
1 cow ≈ 40–60 L/day
1 acre drip irrigation ≈ 15,000–25,000 L/day
1 acre sprinkler ≈ 25,000–40,000 L/day
Small hotel / school ≈ 5,000–15,000 L/day

A normal tap gives about 10 L/min. A shower is 7–12 L/min. The calculator turns your daily volume into the required flow rate using the number of pumping hours you choose.

Static water level — depth to water when the borehole is resting.
Drawdown / dynamic level — how much the water drops when pumping (ask the driller; if unknown use 8–15 m).
Setting depth — place the pump 5–10 m below the lowest expected dynamic level so it never runs dry.
Casing diameter — most Kenyan boreholes are 4", 5" or 6". A 3" pump fits a 4" borehole; a 4" pump needs 5–6".
Yield test — never size a pump larger than about 80% of the tested yield, or the borehole will run dry.

Head is the total height (in metres) the pump must lift. It includes suction, delivery height, pipe friction and the pressure you want at the tap. 10 m of head ≈ 1 bar. A pump rated for 40 m head can deliver water 40 m up (or give strong pressure at a lower height). Always choose a pump whose maximum head is comfortably above your calculated total head.

Pumps lose some power as heat and friction in the pipes and motor. We add about 20% spare capacity and then round up to the next standard motor size. This keeps the pump from running at its absolute limit and gives longer life.

kVA is the size of a generator or inverter. A 5 kVA generator can run roughly 4,000 W of appliances at the same time. Fridges, freezers and pumps pull 2–3× more power for a few seconds when they start. The calculator adds this “surge” so the generator does not trip or stall.

We add up the energy (kWh) you use in a day, divide by the average sun hours (Kenya is usually 5–6) to size the panels, and size the battery for the share of energy you need after dark. Lithium batteries can be discharged deeper than lead-acid, so they can be smaller for the same usable energy.

• Measuring only to the bottom of the tank → pump cannot fill it fully. Measure to the overflow level.
• Ignoring long pipe runs → actual flow is much lower than expected.
• Suction pipe too long or too small → pump loses prime or cavitates.
• Forgetting the tank stand height → head is underestimated by several metres.
• Sizing a borehole pump larger than the tested yield → borehole runs dry and the pump burns.

It is a solid practical guide based on standard hydraulic formulas and the products currently in the Sokokubwa shop. Pump curves differ between brands, so our team always confirms the exact model, pipe size and installation details before you buy.