By the Jordan Pumps team, Kempton Park | Pumps You Can Trust
With load-shedding and municipal outages, more South African homeowners, smallholders and farmers are switching to their own boreholes. The first question we hear is always: “What size pump do I need: 0.37 kW, 0.75 kW or 1.1 kW?”
If the pump is too small, it can’t lift water to your tank. If it’s too big, you pay more and risk running the borehole dry. The good news is that sizing comes down to four numbers, and most of them are in your driller’s report.
Short on time? Enter your water depth into our free Pump Selector Tool. It shows the smallest Jordan pump that can do the job, roughly how much water it will deliver, and the cable size you’ll need.
Step 1: Measure your borehole diameter (3-inch or 4-inch?)
Before you think about power, make sure the pump will physically fit. Borehole pumps are named by the casing they’re designed for:
- 4-inch pumps are the most common choice in SA. They come in more sizes and handle deeper holes and bigger flows.
- 3-inch pumps are made for narrower casings, which you’ll often find in older boreholes.
Check the inside diameter of your casing on your driller’s report or at the wellhead. The pump needs clearance so it can go down and come back up without getting stuck. As a rule, a 4-inch pump needs a casing inside diameter of at least 110 mm, and a 3-inch pump needs at least 80 mm. If your casing is between 80 mm and 110 mm, go with a 3-inch pump. If you’re unsure, ask us first.
Jordan stocks 4-inch pump sets from 0.37 kW to 2.2 kW, 3-inch pump sets in 0.25, 0.37 and 0.55 kW, and ready-to-install 4-inch combo kits.
Step 2: Find your water level, not just the hole depth
A common mistake is sizing for the full depth of the hole. A 100 m borehole might have water at 25 m. What matters is how high the pump has to lift the water, starting from the water level.
Your driller’s yield test should give you:
- Static water level: where the water sits when nothing is pumping.
- Dynamic (pumping) water level: where the water settles while the pump is running. It’s always lower than the static level. Size your pump on this number.
- Recommended yield: how many litres per hour the borehole can safely give. Your pump should never be set up to pull more than this.
If all you know is the total hole depth, use that number instead. You’ll end up with a bit of extra safety margin.
Step 3: Work out your Total Dynamic Head (TDH)
Total Dynamic Head is the total “height” the pump has to push against, measured in metres. Add up:
- Vertical lift: from the dynamic water level up to ground level.
- Height above ground: up to the inlet of your tank, including any tank stand. A JoJo tank on a 3 m stand adds roughly 5 m.
- Friction losses: water rubbing against the inside of the pipe and passing through fittings uses up some of the pump’s head.
- Pressure (only if you pump directly into the house): if the borehole feeds your taps without a tank, add the pressure you want at the tap. 1 bar is about 10 m of head.
Pipe friction, in plain English
Friction goes up quickly with higher flow and narrower pipe. As a rough guide for HDPE pipe (approximate figures, calculated for smooth PN10 pipe):
| Flow | 32 mm HDPE | 40 mm HDPE | 50 mm HDPE |
|---|---|---|---|
| 1,000 L/h | ~1.5 m per 100 m | ~0.5 m per 100 m | ~0.2 m per 100 m |
| 2,000 L/h | ~5.5 m per 100 m | ~1.8 m per 100 m | ~0.6 m per 100 m |
| 3,000 L/h | ~12 m per 100 m | ~4 m per 100 m | ~1.3 m per 100 m |
Add another metre or two for elbows, the non-return valve and other fittings. Tip: if your tank is a long way from the borehole, a larger pipe usually costs less than buying a bigger pump.
Step 4: Decide how much water you actually need
Most systems pump into a storage tank, and a pressure pump then supplies the house. So the borehole pump only has to refill the tank within a few hours, without pumping more than the borehole can give. Rough rules of thumb:
- Household: about 150–250 L per person per day. A family of four uses roughly 600–1,000 L.
- Garden: about 4–5 L per m² every time you water in summer. A 200 m² lawn needs about 1,000 L per watering.
- Smallholding: add livestock, poultry, a veggie tunnel and so on. Count each one separately and add 20% headroom.
- Irrigation: add up the flow rates of every sprinkler or dripper zone that runs at the same time. This is often what decides the pump size.
Divide your daily total by the number of hours you’re happy to run the pump, for example during daylight or outside load-shedding slots. That gives you the minimum flow in L/h.
A worked example
Thandi has a smallholding outside Pretoria. She has a 4-inch cased borehole, a 230 V supply, and a 5,000 L JoJo tank on a 3 m stand about 30 m from the borehole.
- Dynamic water level (from the yield test): 35 m
- Tank inlet height above ground: 5 m
- Pipe: about 70 m of 32 mm HDPE, which at around 1,500 L/h loses ~2.5 m. Add ~1.5 m for fittings: 4 m
- TDH = 35 + 5 + 4 = 44 m
Her family of four plus a veggie garden and some chickens uses about 2,000 L a day, so a pump giving 1,000 L/h or more refills the tank in about two hours. Her yield test says the borehole safely gives 2,500 L/h.
What fits? At 44 m, a 0.37 kW pump set is right at its limit, and the 0.37 kW combo kit would only manage about 1,000 L/h with no headroom. So 0.37 kW is too small. Based on the curves in our selector tool:
- The 0.55 kW borehole combo kit (4-inch) gives about 1,700 L/h at that head. That’s plenty for her needs, it stays under her borehole’s yield, and it comes with 60 m of cable, safety rope and a control box.
- The 0.55 kW 4-inch pump, motor and control box set gives about 3,000 L/h. That’s more than her borehole yields, so it would only suit her with dry-run protection such as the Intelligent Control Box, or if she has a higher-yield hole.
Verdict: the 0.55 kW combo kit, plus a non-return valve and a float switch so the pump stops when the tank is full.
On a three-phase (380/400 V) farm supply? See our 380V pumps and motors, such as the 1.5 kW 4-inch 400 V pump and motor. Keep in mind that these ship as a pump and motor only, so you’ll need a separate starter panel.
Running your pump on a generator or inverter
During load-shedding, many borehole pumps run on a generator or a backup inverter. The supply has to be much bigger than the motor itself. That’s because an electric motor draws several times its running current for a moment as it starts up. If the generator or inverter can’t handle that surge, it will trip or cut out, or the pump won’t start at all.
Use this Jordan sizing table to find the minimum generator or inverter rating for each pump size:
| Pump motor | Minimum generator / inverter rating |
|---|---|
| 1/2 HP (0.37 kW) | 1.5 kW / 1.9 kVA |
| 3/4 HP (0.55 kW) | 2 kW / 2.5 kVA |
| 1 HP (0.75 kW) | 3 kW / 3.8 kVA |
| 1.5 HP (1.1 kW) | 4 kW / 5 kVA |
| 2 HP (1.5 kW) | 5 kW / 6.2 kVA |
| 3 HP (2.2 kW) | 7.5 kW / 9.4 kVA |
| 4 HP (3 kW) | 10 kW / 12.5 kVA |
If the same inverter also runs your house, add the pump’s requirement to everything else that may be switched on when the pump starts.
Don’t forget the cable
Long cable runs need thicker cable. Undersized cable causes voltage drop and tripping. The Pump Selector Tool suggests a cable size from your depth plus the above-ground run. We sell 1.5 mm 3-core submersible cable by the metre, and the combo kits include spliced cable: 50 m (0.37 kW), 60 m (0.55 kW) and 80 m (0.75 kW). Make sure it reaches from the pump all the way to your control box.
Frequently asked questions
What size borehole pump do I need for a normal house?
For a typical home pumping into a tank, with a pumping water level of up to about 30–40 m, a 0.37 kW 4-inch pump or the 0.37 kW combo kit usually does the job. Once your total head goes past about 40 m, step up to 0.55 kW.
Is a bigger pump always better?
No. A pump that pulls more than your borehole’s yield will run it dry and damage itself. Match the pump to your head and your yield.
What’s the difference between 0.37 kW, 0.75 kW and 1.1 kW?
More power mainly buys you more head, meaning the ability to lift water from deeper or push it further. In our range, the 0.37 kW set reaches about 44 m of head at zero flow, the 0.75 kW about 73 m and the 1.1 kW about 102 m. At those maximums the flow drops to almost nothing, so always size with some room to spare.
Can I run my borehole pump on a generator or inverter?
Yes, as long as it’s big enough. Because of the motor’s starting current, a 0.37 kW pump needs at least a 1.5 kW / 1.9 kVA generator or inverter, and a 0.75 kW pump needs at least 3 kW / 3.8 kVA. See the full table under Running your pump on a generator or inverter above.
Do I need a non-return valve?
Yes. We recommend one on every borehole pump installation. It stops the water in the pipe from flowing back and protects the pump from water hammer.
Do you deliver?
Yes. Jordan Pumps delivers nationwide from Kempton Park, and you can spread the cost with Payflex at checkout. Please note that HDPE pipe is collect-only unless arranged with us.
Ready to choose your pump?
Pop your numbers into the Pump Selector Tool, browse our borehole combo kits, or start with our most popular entry kit, the 0.37 kW 4-inch borehole pump combo kit. It includes the motor, pump, control box, 50 m of cable and safety rope.
We deliver nationwide, and you can pay with Payflex to spread the cost.
Still unsure? Send us your driller’s report and we’ll size it for you. Call +27 82 888 0118, email sales@jordangroup.co.za or contact us.
Jordan Pumps: Pumps You Can Trust.
Flow and head figures are approximate and based on the performance data in the Jordan Pump Selector Tool. Water-use figures are general rules of thumb. Always check against your own borehole yield test.
