How a Borehole Is Drilled: Step by Step

Most Johannesburg homeowners who enquire about a borehole have the same mental image: a big truck arrives, drills a hole, and water comes out. The reality is a structured, multi-stage process where each step builds on the last. Knowing what should happen — and roughly when — puts you in a far stronger position when you’re comparing contractors and overseeing the work.

For a broader picture of what a complete system involves and what drives cost, the borehole drilling guide covers the full landscape. This article focuses specifically on the drilling process itself, day by day.

Stage 1: Site Assessment and Borehole Siting

Before any equipment arrives, a competent contractor will assess your property to identify the most promising drilling location. This is not guesswork, but it is not an exact science either.

Siting typically involves one or more of the following:

• Geological mapping — reviewing published hydrogeological data for your area of Johannesburg, since the underlying geology (dolomite, granite, shale and so on) strongly influences where water-bearing fractures are likely to occur.
• Geophysical survey — some contractors use resistivity or electromagnetic methods to detect sub-surface water-bearing zones. This adds cost but reduces risk, particularly on properties where dolomite is a concern.
• Local knowledge — an experienced driller who has worked extensively in your suburb will have practical data on typical yields and depths in that area.

The siting stage also involves checking servitude maps and municipal bylaws. In Gauteng, water use registration requirements under the National Water Act apply once abstraction exceeds a threshold — your contractor should be across this, and the Department of Water and Sanitation (DWS) is the relevant authority.

Expect siting to take a few hours to a half-day. If a contractor skips this entirely and drills wherever the truck parks, that is a red flag.

Stage 2: Mobilisation and Rig Setup

The drilling rig — typically a truck-mounted rotary or percussion rig — needs reasonable access to the chosen site. On a standard Johannesburg suburban plot this is usually manageable, but tight access, slopes, or overhead cables can complicate things and should be flagged in advance.

Setup involves positioning the rig, levelling it, and assembling the drill string. The contractor will also organise water supply for the drilling process itself (drilling uses water or air, depending on method), as well as a plan for managing drill cuttings — the material brought up from below ground as drilling progresses.

Setup typically takes half a day to a full day.

Stage 3: Drilling

This is the stage most people associate with the whole job. The rig drives the drill bit into the ground, progressively adding drill rods as depth increases. Cuttings are continuously flushed to surface, and the driller monitors these carefully — the colour, texture, and mineralogy of cuttings indicate what formation is being drilled through and whether water-bearing zones have been encountered.

In Johannesburg, target depths vary considerably by area and geology. As a rough guide, many residential boreholes reach between 60 and 150 metres, but your actual depth will depend entirely on where your water-bearing fracture sits. Deeper is not automatically better — what matters is intersecting a productive aquifer.

Once a water strike is identified, the driller will note the depth and continue to a point that optimises yield without unnecessary cost. Air rotary and down-the-hole hammer drilling are the most common methods used in hard-rock Johannesburg geology.

Drilling typically takes one to two days for a standard residential borehole, though difficult ground or deeper targets can extend this.

Stage 4: Casing and Grouting

Steel or uPVC casing is inserted from surface to a depth that seals out surface water and unstable near-surface material. Casing protects the borehole integrity and is critical to water quality — without proper casing, surface contamination (garden chemicals, sewage, stormwater) can migrate directly into your water supply.

The annular space between the casing and borehole wall is grouted at the surface section to form a sanitary seal. This step is non-negotiable for a compliant installation and is referenced in SANS 241 (2024 edition), the South African drinking-water quality standard, in the context of protecting source water.

Below the casing, a slotted liner or screen is often installed across the productive water-bearing zone to allow water inflow while keeping fine material out.

Stage 5: Airlift Testing and Yield Assessment

Before the pump goes in, the contractor should conduct an airlift test — compressed air is injected into the borehole to purge drilling debris and simultaneously measure how much water the borehole produces. This gives a preliminary yield figure, typically expressed in litres per hour.

Yield matters because it determines what pump is appropriate and whether the borehole will realistically meet your household demand. A borehole that looks clean and deep can still be low-yielding. Do not skip this step or accept a pump recommendation without a yield figure.

Airlift testing is usually completed within a few hours.

If you're still comparing your options before committing to a driller, it helps to have a few numbers side by side. Compare 3 free quotes — vetted installers, no obligation.

Stage 6: Pump Selection and Installation

With a yield figure in hand, the contractor selects a submersible pump rated appropriately for your borehole’s output and your household’s needs. Oversizing a pump relative to yield will cause the borehole to run dry repeatedly, damaging the pump motor. Undersizing it means you won’t get the flow rate you need at the tap.

The pump is lowered on a rising main (typically HDPE pipe) to the correct depth below the standing water level. A pump controller or starter box is installed at surface, along with pressure switches and, where relevant, a pressure tank to moderate pump cycling.

Borehole pumps typically cost R15,000–R35,000 installed, within the broader system cost range of R40,000–R150,000 for a complete borehole system in Johannesburg, with most residential installations falling between R60,000 and R100,000. These are verified typical ranges — get itemised quotes to confirm what applies to your property.

Stage 7: Water Quality Testing

A newly drilled borehole is not automatically safe to use for drinking or cooking. Borehole water must be tested against SANS 241 (2024 edition) before any potable use. Testing covers microbiological contaminants, chemical parameters, and physical characteristics.

Your contractor should facilitate this by collecting a water sample from the installed system and sending it to an accredited laboratory. Results typically take a few days to a week. Based on those results, a filtration or treatment system may be recommended — UV sterilisation, sediment filtration, and chemical dosing are all options depending on what the test reveals.

Do not use borehole water for drinking without a SANS 241-compliant test result in hand. This applies even if the water looks and tastes fine.

Once you know what the process involves, the next step is finding a contractor who will actually follow it. Get free quotes from vetted drillers and ask each one to walk you through their process stage by stage.

What to Ask Your Contractor Before They Start

Now that you understand the sequence, here are the practical questions that separate a thorough contractor from a shortcutting one:

• Will you conduct a site assessment and explain your siting rationale before drilling?
• What drilling method will you use, and why is it appropriate for this site’s geology?
• What depth are you targeting, and what’s your contingency if you don’t hit yield at that depth?
• Will you install casing and grout the annulus?
• What does your airlift test report look like, and will I get a copy?
• How do you select pump size relative to measured yield?
• Do you arrange SANS 241 water quality testing, or is that my responsibility?

A contractor who answers these questions clearly and without irritation is worth taking seriously. One who brushes them off warrants caution — the borehole drilling overview has more on what to look for when evaluating quotes.