Borehole pumps explained: types, uses, and how they work

Borehole pumps are pumps that lift groundwater from a drilled well to the surface, usually from below the water level. If you own a private well in Germany, run a farm or install water systems, the choice between a submersible unit and a surface pump decides pressure, running cost and service life. This guide explains the main types of borehole pumps, how they work, where they are used and how to size them without guessing. Why do so many buyers pick the wrong head? Usually because they only look at the flow figure on the data sheet. We fix that with a clear calculation method, a worked example and a checklist you can use before comparing quotes. Where numbers are illustrative, we say so.

What borehole pumps are and how they work

A borehole pump moves water by pushing it upward from inside the well. A sealed motor turns a stack of impellers, each stage adds pressure, and the water rises through the riser pipe. Because the unit sits below the water level, it pushes water rather than sucking it. That single fact explains why borehole pumps keep working where surface pumps give up.

How a submersible borehole pump moves water

Inside a submersible pump, water enters through an intake screen, reaches the first impeller and is thrown outward by centrifugal force. A diffuser then turns velocity into pressure and guides the flow to the next stage. Multi-stage designs stack many stages, so the head grows stage by stage. For a general introduction to how pumps work, Britannica is a solid reference. A check valve at the top keeps the water column from draining back when the pump stops.

Main components

A typical submersible well pump has four groups of parts: the hydraulic end (impellers and diffusers), the motor, the cable with its splice, and the riser pipe with check valve. Many single-phase units are sold as a borehole pump with control box, where the box holds the start capacitor and protection relay. Three-phase units use a motor-protection switch or a frequency inverter instead. A stainless steel borehole pump uses corrosion-resistant sleeves and shafts, which matters in aggressive or sandy groundwater.

What is the difference between a borehole pump and a well pump?

The terms overlap. "Borehole pump" is the usual international term. In German you will see Brunnenpumpe or Tiefbrunnenpumpe, and "deep well pump" or "groundwater pump" describe the same job. The real distinction is design. Submersible units sit in the water, while line-shaft deep well pumps keep the motor at the surface and drive the impellers through a long shaft. Shallow garden pumps (Gartenpumpen) stay above ground and rely on suction. Installers often tell us that confusion over names leads to wrong orders, so always confirm diameter and head, not just the product label.

Types of borehole pumps and when each one fits

The main types of borehole pumps are submersible, line-shaft deep well, jet and solar-powered units. Submersible pumps dominate private wells. Line-shaft designs suit very deep or high-volume wells. Jet pumps cover moderate depths, and solar variants suit sites without grid power.

Submersible and deep well pumps

A submersible borehole pump is the default choice for drilled wells from a few metres up to well over 100 m, depending on stage count and motor power. It is quiet, self-priming by nature and protected from frost underground. A line-shaft deep well pump costs more to install, but it keeps the motor accessible for service. Some manufacturers also list a canned (shielded-motor) deep well pump as a separate category. Check the data sheet for the exact construction, because the term is not used identically everywhere.

Jet and surface alternatives

Surface pumps are limited by atmospheric pressure. The theoretical suction lift is about 10.33 m at sea level, and in practice roughly 7 to 8 m is realistic. Deep-well jet pumps place an ejector in the well and reach further, but they are usually louder and less efficient than multi-stage submersibles. A Hauswasserwerk (domestic water station) with a surface pump is fine for shallow driven wells. Beyond that depth, borehole pumps are the better fit.

Solar borehole pump

A solar borehole pump runs from photovoltaic panels through a controller, often with an MPPT function, and stores water in a tank instead of storing energy in batteries. Flow follows sunlight. That suits summer irrigation and remote pastures very well. Of course, German winter yields are low, so a solar borehole pump is rarely a year-round solution for a household without a backup.

Table note: depth ranges are general engineering orientation values. Always verify against the manufacturer's curve for the specific model.

Common uses of borehole pumps in Germany

Borehole pumps mainly supply household water, garden and field irrigation, livestock water and small commercial or process needs. The use case defines the required flow, pressure and duty cycle. A garden sprinkler runs a few hours a week, while a dairy trough may demand water every day.

Household supply and garden irrigation

Many German gardens use shallow driven wells (Rammbrunnen) with a surface pump. A drilled well with a borehole pump for garden irrigation makes sense when the groundwater lies deeper, when the surface pump is too noisy, or when you want stable pressure. A 4-inch submersible well pump with a pressure tank is a common pairing in residential setups. Watering lawns and beds with well water is generally uncontroversial. Using it as drinking water is a different matter, covered below.

Farms, livestock and small commercial use

Farmers use borehole water pumps to fill storage tanks, feed trough systems and irrigate vegetable plots or orchards. Higher flows usually call for three-phase motors and larger bore diameters. A tank-based layout reduces start-stop cycles, which is gentler on the motor than direct pressure control. In practice, farm projects fail less often from the pump itself than from undersized cables and missing dry-run protection.

Can borehole pumps supply drinking water?

Technically yes, but the pump is only one link in the chain. Water quality depends on the aquifer, well construction and treatment. The U.S. Environmental Protection Agency summarises the principle clearly for private water wells:

According to the U.S. EPA, private wells are not covered by federal drinking water regulations, so owners are responsible for testing, maintaining and protecting their own water supply.

German rules differ in detail. The Trinkwasserverordnung and local authorities (Gesundheitsamt, Untere Wasserbehörde) set requirements, especially when water is passed on to others. For health-related questions, consult a qualified professional or your local authority.

How to size borehole pumps: head, flow and the pump curve

To size borehole pumps, add the pumping water level, the required outlet pressure and the pipe friction loss to get the total head (Förderhöhe). Then choose a pump whose curve delivers your flow (Förderstrom) at that head. Flow alone never decides the selection.

Step-by-step head calculation

1. Measure the dynamic water level (dynamischer Wasserspiegel): the depth of the water surface while the pump is running, in metres below ground.
2. Add the vertical distance from ground level to the highest tap or tank inlet.
3. Convert the required outlet pressure to metres of head: multiply bar by 10.2.
4. Estimate friction loss (Druckverlust) in pipes and fittings using the pipe manufacturer's tables for your flow rate.
5. Add all values to obtain total head, then check the pump curve for your flow in m³/h and keep a modest reserve.

Worked example: garden irrigation at 3 bar

The following is an illustrative calculation, not a customer case. Assume a garden sprinkler system that needs 3 m³/h (50 L/min) at 3 bar, with the dynamic water level at 28 m. Friction loss of 4 m is assumed for the riser and supply pipe.

So the target operating point is about 3 m³/h at roughly 63 m. A pump whose maximum head is only 65 m would sit at the end of its curve, which is inefficient and risky. Choose a model where this point lies in the middle of the curve.

Reading the pump curve

Every curve shows head falling as flow rises. Look for the best efficiency point (BEP) and try to place your duty point near it. Oversizing is the classic error: a pump with far too much head is throttled by a valve, and the surplus energy turns into heat and noise. Think of it as driving a lorry to fetch bread. It works, but it is wasteful. Many German installers like a small head reserve, but not a large one.

Specifications that matter: 4-inch size, materials and control box

The three specifications that most often decide fit are the pump diameter, the wetted materials and the electrical control. A pump that does not fit the casing, corrodes in your water or lacks protection will cost far more than the price difference suggests.

The 4 inch borehole pump

A 4 inch borehole pump has an outer diameter of roughly 96 to 100 mm, so it needs a casing with an inside diameter of at least 100 mm. Many installers prefer 125 mm (5 inch) casing for clearance, easier cable handling and better motor cooling. This size covers most household and garden applications and a good range of small farm duties. Larger flows and deeper settings often move to 6-inch or larger units. Always compare the diameter in the data sheet with your actual casing, not the nominal drilling size.

Stainless steel and other materials

A stainless steel borehole pump is the common choice for long service in groundwater with moderate corrosiveness. Grades such as AISI 304 and 316 are widely used, with 316 offering better resistance in chloride-rich water. Cast iron is cheaper but corrodes more readily, and technical polymer impellers are lightweight and cost-effective. No material is immune to sand abrasion. If your water carries sand, improving well development and screen selection usually pays off more than a material upgrade.

Control box, pressure switch and inverter

A borehole pump with control box simplifies single-phase starting, since the box contains the capacitor and relay. Add dry-run protection, which prevents the motor from running when the water level drops. A pressure tank with a pressure switch limits starts per hour. A frequency inverter keeps pressure constant and softens starts, but it adds cost and needs correct cable and filter selection. The best setup is the simplest one that meets your pressure stability needs.

Borehole pump installation: planning, steps and common mistakes

Borehole pump installation requires a clean, developed well, a correct setting depth and a safe electrical connection. In Germany, groundwater use may require notification or permission, and electrical work should be done by a qualified electrician.

Before you start: permits and drilling

Contact the Untere Wasserbehörde early. Rules on drilling, groundwater extraction and notification vary by Bundesland and by purpose. The well itself is created with professional water well drilling equipment and should be developed until the water runs clear before any pump is lowered. Installing a pump in a freshly drilled, sandy well is a common reason for early failure. Skipping well development saves a day and can cost a pump.

Step-by-step installation

1. Record well depth, casing diameter, static and dynamic water level and any sand content.
2. Check that pump data (head, flow, diameter, voltage) match your calculation.
3. Attach the riser pipe and a stainless safety rope, and fit the check valve as specified.
4. Secure the motor cable to the riser pipe at regular intervals, and protect the splice.
5. Lower the unit slowly. Never lift or lower by the cable.
6. Set the pump well below the lowest pumping level and clear of the well bottom sediment.
7. Connect the well head, control box and protection. Start against a partly closed valve until the water runs clear.
8. Record current draw, flow and pressure as a baseline for later service.

Common mistakes

Typical errors include placing the pump in sediment, undersizing the cable (voltage drop at 40 m of cable is real), omitting dry-run protection and ignoring the check valve. Another is mixing up the static and dynamic water level when calculating the setting depth. Why does this happen so often? Because the static level is what you measure on a calm day. Of course, in a very productive aquifer the difference may be small, but you should still check it.

Borehole pump price, running costs and maintenance

Borehole pump price depends mainly on stage count, motor power, materials and included electronics. For pumps running long hours, energy cost can exceed the purchase price over their life, so efficiency deserves as much attention as the sticker.

What drives the borehole pump price

The main drivers are the number of stages, motor rating, wetted materials (stainless steel versus cast iron), phase type and whether the set includes a control box, cable and riser. We deliberately give no fixed euro figures here, because prices change with raw materials and exchange rates. Request itemised quotes that list pump, cable, control box, riser pipe, check valve and installation separately. That makes offers genuinely comparable. Many suppliers offer pump families covering submersible, jet, centrifugal and deep well types plus matching motors, which simplifies pairing, but always verify each data sheet individually.

Energy cost example

Using the earlier example (0.51 kW hydraulic power), the table shows how overall efficiency (wire to water) changes yearly cost. Assumptions: 300 operating hours per year and an electricity price of €0.35 per kWh. These are illustrative values, so replace them with your own tariff.

In this scenario, the gap between 35 % and 55 % is about €56 per year. For a garden that is modest, but for a farm running 3,000 hours it is ten times larger. Duty hours decide how much efficiency is worth paying for.

Maintenance and service life

Service life varies widely with water quality, sand, start frequency, voltage and dry running, so no honest source can promise a fixed number of years. Practical habits help: log current and pressure annually, check the pressure tank pre-charge, and test the water if taste or colour changes. If flow drops, look at the well screen, riser pipe and check valve before blaming the pump.

Conclusion: choosing borehole pumps with confidence

Good borehole pumps are chosen by total head, not by flow alone. Calculate the Förderhöhe, check the diameter against your casing, pick materials that suit your water and add proper protection. Then compare itemised quotes on price and efficiency together. Whether you need a submersible borehole pump for a garden, a solar borehole pump for a pasture or a deep well pump for a farm, the method stays the same. For local permits and drinking-water use, consult your authority or a qualified installer.