Table of Contents
A pump for drip irrigation in Kenya has one job: deliver the flow the system was designed for, at the pressure the tape needs, for the hours the design assumes. Most pump failures begin before the pump is bought, because nobody calculated the flow and the head first.
First, this page works through both numbers on a one-hectare block. Then it covers the pump types sold here, the power source, the installation details that decide how long the pump lasts, and the questions to ask before you pay.
What a pump for drip irrigation must do
Drip tape and drip line run at low pressure. Typically, the window is between 1.0 and 1.5 bar at the tape inlet, the same as 10 to 15 metres of head. Below 1.0 bar the far end of a long lateral emits less than the near end, and the crop rows water unevenly. Above 1.5 bar, however, the joints start to leak and the tape can split.
In practice, that low pressure fools buyers into thinking the pump choice is simple. It is not. Moreover, the pump has to supply the right volume, and volume is set by the emitters, not by the pressure. For example, a pump that delivers 2 bars and 3 cubic metres an hour will starve a system designed for 16 cubic metres an hour, however healthy the pressure gauge looks.
Horsepower is the worst number to shop by. In addition, two pumps labelled 2 HP can deliver very different flows at the same head, depending on impeller design and efficiency. Therefore, the duty point, a flow in cubic metres an hour at a head in metres, is the only description that lets you compare two pumps.
How to size a pump for drip irrigation
Start with the emitters, because every litre a pump for drip irrigation moves leaves through one of them. The formula is simple: flow in cubic metres an hour equals the number of emitters multiplied by their discharge in litres an hour, divided by 1,000.
Take a one-hectare block. At 1 metre row spacing the block carries 100 rows, each 100 metres long. Specifically, tape at 30 centimetre emitter spacing gives 333 emitters per row, so the block holds about 33,300 emitters. At 2 litres an hour each, the whole block would draw 66.6 cubic metres an hour if every row ran at once.
No sensible design does that. Instead, the block is split into four irrigation zones, and each zone runs alone. One zone carries about 8,325 emitters, which draws 16.65 cubic metres an hour. That is the flow the pump must hold, and the other three zones wait their turn.
Zoning is the cheapest way to shrink a pump. Similarly, four zones need a quarter of the flow of one big block, and the pump, the mainline and the solar array all shrink with it. A grower who skips the zoning step ends up buying a pump three sizes too large. Then the same pump is throttled with a valve to protect the tape.
Head: the five parts of total dynamic head
Flow is half the duty point of a pump for drip irrigation. Head is the other half, and it is the number buyers underestimate. Therefore, total dynamic head adds five things: the static lift from the water level to the field, the drawdown while the pump runs, friction in the pipes, an allowance for the filters, and the operating pressure at the tape.
Here is the same one-hectare block on a borehole. The water sits 35 metres below ground, and the level drops 8 metres while the pump runs, so the lift is 43 metres. Next, the delivery main is 150 metres of 63 millimetre pipe at 16.7 cubic metres an hour, which loses about 5 metres. Meanwhile, the sand and screen filters add roughly 5 metres when clean. The tape needs 12 metres, or 1.2 bar. Thus the total is 65 metres of head.
| Pipe size | 5 m³/h | 10 m³/h | 15 m³/h | 20 m³/h |
|---|---|---|---|---|
| 32 mm | 9.7 m | 35.1 m | 74.4 m | 126.7 m |
| 40 mm | 3.3 m | 11.8 m | 25.1 m | 42.7 m |
| 50 mm | 1.1 m | 4.0 m | 8.5 m | 14.4 m |
| 63 mm | 0.4 m | 1.3 m | 2.7 m | 4.7 m |
Friction loss per 100 metres of uPVC pipe at C = 150, calculated with Hazen-Williams.
Those figures are friction loss per 100 metres of uPVC at a roughness coefficient of 150, calculated with the Hazen-Williams equation. For instance, read the 32 millimetre row at 15 cubic metres an hour: 74 metres of head lost in every 100 metres of pipe. No pump can fix that. The pipe is the problem, and upsizing it to 63 millimetres cuts the loss to 2.7 metres.
This is where most oversized pumps come from. As a result, a grower adds head for a long run of small pipe and buys a bigger pump to push through it. That decision is paid for twice: once at the counter, and again every month in energy.
Reading a pump curve against the system curve
Every pump has a curve that slopes down: more flow means less head. Similarly, every drip system has a curve that rises: more flow means more friction. Therefore, the duty point is where the two cross, and a pump only works well near it.
Run the pump far to the right of that point, with a wide-open valve and more flow than the design, and the motor draws more current than it should. Conversely, run it far to the left with a throttled valve and the water recirculates inside the casing and heats up. Both shorten the pump’s life, and neither shows on a pressure gauge as an obvious fault.
Power follows the duty point. For this reason, a pump moving 16.7 cubic metres an hour against 65 metres of head absorbs about 5.4 kilowatts at 55 percent efficiency. The same duty at 45 percent efficiency needs 6.6 kilowatts, which is why two pumps with the same flow rating can carry very different running costs. Finally, ask for the efficiency at your duty point, not at the pump’s best point.
Types of pump for drip irrigation in Kenya
Four kinds of pump for drip irrigation cover almost every farm here. The water source decides which one, and the head decides the model inside that kind.
- Submersible pumps. They sit below the water surface in a borehole, well or deep tank. A 4-inch pump fits a 4-inch casing, and a 6-inch pump is more efficient where the casing allows it. They need a rising main, a cable and a non-return valve.
- Surface centrifugal pumps. They stand beside a dam, river or shallow well and suck water up through a suction hose. Typically, suction lift is rarely more than 7 metres, and less at altitude, so they suit surface water and not deep boreholes.
- Booster pumps. They add pressure to water that already arrives from a tank or a gravity main. Similarly, they run at low head and high flow, and a pressure switch or float controls them.
- Solar submersible kits. A DC pump, a controller and an array, sold as a matched set. Output rises and falls with the sun, so the pump fills a tank through the day.
For a borehole, the pump setting matters as much as the model. The intake goes below the drawdown level and above the top of the screens, so the pump never runs dry and never pulls silt.
Solar, grid or diesel: matching the power source
The power source for a pump for drip irrigation is a question of when it runs and how many hours a day. Drip rewards long, steady hours at low flow, and that shape suits some sources better than others.
| Source | Fits | Main cost | Main risk |
|---|---|---|---|
| Solar | Daytime irrigation, 4 to 6 hours, off-grid sites | Array and controller at the start | Output falls on cloudy days |
| Grid | Steady daily volumes, night or off-peak pumping | Connection and monthly units | Outages stop the water |
| Diesel or petrol | Portable, high-flow, short bursts | Fuel and servicing | Running hours cost money daily |
Power sources compared on fit, main cost and main risk.
Solar sizing starts from daily energy. For example, a 5.4 kilowatt pump running six hours uses about 32 kilowatt hours a day. At four to five peak sun hours, the array then needs roughly 8 kilowatts peak once losses are counted. The tank does the rest, storing the day’s water for the evening irrigation.
A grid connection suits a farm that already has power. It also lets the pump run at night. Meanwhile, a diesel pump suits a site where the water moves between blocks, and the pump travels with it. On a borehole with no grid and no reliable fuel supply, the solar kit is usually the only source that keeps running.
Five installation details that decide pump life
- Filter order. Water leaves the pump and enters a sand media filter, then a screen or disk filter at 120 mesh, then the mainline. Gauges either side of each filter show when it needs cleaning.
- Non-return valve. It sits after the pump and stops water running back through the casing at shutdown, which protects the impeller and keeps the suction line primed.
- Pressure regulation. A regulator or bypass holds the tape at 1.2 bar. Without it, a pump sized for a dirty filter will overpressure the tape on the day the filter is clean.
- Dry-run protection. A low-level probe in the tank or a float switch in the sump stops the pump when water runs out. A borehole pump also needs its intake set below the drawdown level.
- Air and water hammer. An air valve at the highest point lets air out on start-up, and a slow-closing valve stops the pressure spike when the pump stops.
The borehole side of a pump for drip irrigation deserves its own check. A pump that draws more than the borehole can replenish will pull the water level down to the intake, run dry and burn the motor. Therefore, the yield test from the driller gives the safe pumping rate, and the pump is chosen below it.
Seven mistakes in buying a pump for drip irrigation
These are the errors that turn a working design into a repair bill. Nevertheless, each one is cheaper to avoid at the quotation stage than to fix in the field.
- Buying by horsepower. The label says nothing about flow at your head. Ask for the duty point.
- Sizing for the whole field. A one-hectare block at 66 cubic metres an hour needs four zones, not a giant pump.
- Leaving drawdown out of the head. The water level drops while the pump runs, and that drop is real head.
- Undersizing the delivery main. A 32 millimetre main at 15 cubic metres an hour wastes 74 metres of head per 100 metres.
- No filter before the tape. Silt and algae reach the emitters, and clogged tape costs more than the filter.
- No pressure regulation. The tape splits at the joints, usually in the first week after a clean filter.
- No dry-run protection. The pump runs dry once and the motor is scrap, which is the most expensive failure on the list.
Frequently asked questions about a pump for drip irrigation
These are the questions we are asked most frequently about pump size and pressure.
What size pump do I need for one acre of drip?
About 13.5 cubic metres an hour per zone, with the acre split into two zones. Typically, one acre carries roughly 13,500 emitters at 30 centimetre spacing and 2 litres an hour, which is 27 cubic metres an hour for the whole block. Then add the head for your water source, and you have the duty point.
Can a pump be too big for drip irrigation?
Yes. For example, an oversized pump overpressures the tape, strains the joints and hammers the pipeline at every start. It also draws more power than the design needs, so the running cost stays high for the life of the system.
How much pressure does drip tape need?
Between 1.0 and 1.5 bar at the tape inlet, or 10 to 15 metres of head. Most designs settle near 1.2 bar, and a pressure regulator holds that figure whatever the pump delivers.
Can I run drip irrigation from a gravity tank?
Yes, if the tank sits high enough. In practice, the tape needs about 12 metres of fall for the pressure alone, plus 5 to 8 metres for friction and filters. That puts the tank roughly 20 metres above the highest tape, which is a tall stand but a cheap system to run.
Will a solar pump water my crop at night?
Not directly. A solar pump runs when the sun shines, so the design stores water in a tank through the day and irrigates from the tank in the evening. The tank replaces the battery, and it costs less to maintain.
What does a borehole yield test tell me?
Typically, it gives the pumping rate the borehole can sustain and the drawdown at that rate. Both numbers go into the head calculation, and the safe yield caps the pump size. Without the test, the pump is a guess.
Where to get a pump for drip irrigation in Kenya
Eunidrip Irrigation Systems sizes a pump for drip irrigation from your emitter count, your water level and your pipe run, then supplies and installs it. Bring the plot size, the water source, the static water level and the distance to the field, and the duty point can be calculated before anything is ordered.
The solar pump sets are listed on the shop at solar pumps for sale in Kenya, priced by quotation because the array and pump change with the head. For the wider system, see solar irrigation in Kenya and the best drip irrigation system guide. Where one pump cannot carry the flow, the pumps in parallel page covers the manifold design, and the borehole drilling page covers the yield test in detail.
Call +254 728 163329, or dial +254 724 775516, with the four figures: area, emitter flow, static water level and delivery distance. You will get a duty point, a pump model and a quote in the same conversation.