Which Solar Pump Do I Need for a 100m Borehole?

Short answer: it depends on where the water stands in the borehole, not how deep the hole is. A 100m borehole with water at 40m needs a much smaller pump than one with water at 95m. Work out your total head first, then choose a pump rated comfortably above it.

Step 1: Use the water level, not the borehole depth

The pump only has to lift water from the water level (the "static level" on your driller's report) to the top of your tank. The extra depth below the water level only tells us how deep the pump can hang.

Total head = water level + tank height above ground + about 10% for pipe friction (more for long or thin pipes).

Step 2: Leave headroom

A pump's flow drops sharply as it nears its maximum head. We choose a pump whose maximum head is at least 20% above your total head, then read its pump curve at your head to see the real flow.

Three examples for a 100m borehole

Each example has a 6m tank stand and a short pipe run. Flows are read from the manufacturer's pump curves; daily water assumes about 6 good sun hours.

Water level at 40m (total head about 51m)

• PUSC77 screw pump: about 650 L/h, roughly 3,900 L a day. Good for a household.
• PUBO95 centrifugal pump: about 2,200 L/h, roughly 13,000 L a day. For gardens and livestock.

Water level at 70m (total head about 84m)

• PUSC10 screw pump (109m): about 750 L/h, roughly 4,500 L a day.
• PUBO123 centrifugal pump: about 1,900 L/h, roughly 11,000 L a day.

Water level at 95m (total head about 111m)

• You need a pump rated well above 111m, such as the PUBO140 or the PUBO203. Send us your details and we'll check the curve for your exact head.

What else changes the answer?

• Pipe size and distance: a long run of thin pipe adds friction, which counts as extra head.
• Water needed: a household needs about 150–250 L per person per day; livestock and irrigation need far more.
• Borehole yield: the pump should not take more water than the borehole delivers. Your driller's test gives the safe yield.

Let us check it for you

Try our pump selector: answer 7 quick questions and it suggests pumps and sends your answers to us. Or read the full guide to choosing a solar borehole pump.

The Sun Pays has supplied solar power, AC and DC water pumps and solar water heating across South Africa since 2007, with our own South African technical team for advice, repairs and support. Questions? WhatsApp 082 515 1655, call 012 734 0915 or email sales@thesunpays.co.za.

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