The Borehole Drilling Process, Step by Step

Knowing what happens underground before, during and after drilling day is the difference between a homeowner who can hold a contractor to account and one who simply hopes for the best. This walkthrough covers every stage of the borehole drilling process in plain terms, so you know what to expect and what to question.

Stage 1: Hydrogeological Siting

Before a rig arrives, someone needs to work out where to drill. Johannesburg sits on the Witwatersrand ridge, where water-bearing fractures in hard rock are the target — not the porous aquifers common in sandier geology elsewhere in the country. Getting the location wrong can mean a dry or low-yielding hole that still costs you the full drilling fee.

A competent siting exercise typically involves a review of regional geological maps, sometimes a surface geophysical survey (electrical resistivity or ground-penetrating radar), and an experienced eye for surface indicators such as fault lines, drainage patterns and vegetation. Some contractors skip formal siting and rely on experience alone; this is a risk worth discussing upfront. The siting recommendation should be documented in writing before drilling begins.

For a broader overview of what drives cost and yield across the full project, the borehole drilling guide covers the Johannesburg context in more detail.

Stage 2: Rig Mobilisation and Setup

Once a site is chosen, the drilling contractor mobilises. For most residential properties in Johannesburg this means a truck-mounted percussion (cable-tool) or rotary air rig, access for which requires a clear path of roughly three to four metres wide and overhead clearance for the mast. Confirm these requirements with your contractor before the day — a rig that cannot reach the sited position creates expensive delays.

The crew will typically mark the borehole collar position, set up a water supply for drilling fluid if needed (rotary rigs use more water than percussion), and create a small sump or containment area for drill cuttings and return water. Check that they protect surrounding paving and vegetation — damage to your property during setup is not uncommon and is easier to prevent than to claim back.

Stage 3: Drilling

Actual drilling time depends on depth, rock hardness and the method used. In Johannesburg’s hard rock environment, percussion drilling (the heavy bit hammering downward) is common and reliable, though rotary air (down-the-hole hammer) rigs are increasingly used for speed. Soft overburden near the surface — often a metre or two of soil and weathered rock — progresses quickly; consolidated quartzite or granite below that is slower.

Drill cuttings (small rock chips and dust) are returned to the surface throughout drilling. A good contractor logs these cuttings by depth, noting changes in rock type, colour and moisture. This drilling log is a useful document: it tells you where water strikes occurred and at what depth. Ask for a copy — reputable contractors provide one as standard.

Depth varies considerably depending on where water is encountered. Many Johannesburg residential boreholes reach water at 40–80 metres, though some go considerably deeper. You cannot know the final depth in advance, which is why what affects borehole drilling price is worth reading before signing any contract — depth is usually the single biggest cost variable.

Stage 4: Casing and Grouting

Once the target depth is reached, steel or uPVC casing is installed in the upper section of the borehole. Its purpose is twofold: to stabilise the hole through unconsolidated or fractured near-surface material, and to seal out surface contamination — runoff, fertilisers, septic seepage — that could pollute the water column.

The annular space between the casing and the borehole wall in the upper two to five metres should be grouted with cement. This is a step that is sometimes skipped or done poorly on cheaper jobs, yet it is one of the most important for long-term water quality. Confirm in writing that grouting is included and check that it has been done before the rig leaves site.

Below the cased section, the open borehole in solid rock is self-supporting and does not require casing, though a slotted liner is sometimes fitted to stabilise fractured zones.

If you want to compare what different contractors actually include in their casing and grouting specifications, get three free quotes side by side — vetted installers, no obligation.

Stage 5: Borehole Development

A freshly drilled borehole is not ready to use. The drilling process leaves fine rock particles, drilling fines and disturbed material around the fractures that feed the hole. Development — typically air-surging or high-volume pumping — flushes this material out and opens up the natural fractures so the borehole yields its sustainable rate rather than an artificially restricted one.

A proper development phase should run for several hours, often continuing until return water runs clear. The contractor should then conduct a basic yield test: pumping at a steady rate while measuring the drawdown (how far the water level drops) and recovery (how fast it returns after pumping stops). This gives you an estimated sustainable yield — typically expressed in litres per hour or kilolitres per day — which determines what pump and storage setup you actually need.

Skipping or shortcutting development is a common way to save time on site. A hole that has not been properly developed may appear to yield well on the day but underperform once a pump is installed and regular use begins.

Stage 6: Pump Selection and Installation

With a yield figure in hand, the contractor or a separate pump specialist selects a submersible pump sized to match the borehole’s sustainable output and your household demand. Oversizing the pump relative to yield leads to pump burnout; undersizing wastes the potential of a good aquifer.

Borehole pumps typically cost R15,000–R35,000 installed, depending on depth, flow rate and brand. The pump is suspended on rising main (delivery pipe) and a safety cable, with the power cable clamped alongside at regular intervals to prevent chafing. A wellhead cover is fitted at surface, along with a pressure switch, check valve and isolation valves.

For the pipework from the wellhead into your home — header tanks, pressure vessels, isolation from the municipal supply — connecting a borehole to your house covers the practical detail. Typical complete systems in Johannesburg run R40,000–R150,000, with most residential installations falling between R60,000 and R100,000 once all components are included.

Stage 7: Water Quality Testing

Yield is only half the picture. Groundwater in Johannesburg can contain elevated iron, manganese, fluoride, nitrates or microbial contamination depending on local geology and surface activity. The relevant benchmark is SANS 241 (2024 edition), South Africa’s drinking-water quality standard.

A reputable contractor will recommend an accredited laboratory water test before you use borehole water for drinking or cooking. The test panel should cover microbiology (E. coli, total coliforms) and the key chemical parameters. Results take a few days and cost a modest amount relative to the overall project — do not skip this step or accept a verbal assurance that the water looks clear.

If results show elevated parameters, the contractor or a water-treatment specialist can recommend point-of-entry filtration or UV disinfection. The Department of Water and Sanitation (DWS) regulates groundwater use and its guidance on private borehole registration is worth reviewing before commissioning your system.

Knowing the process is useful; knowing which local contractors follow it properly is the harder part. Request three comparable quotes from installers who work to this standard — no cost, no commitment.

What to Keep on File

Once the project is complete, you should hold: the drilling log with depth and cuttings record, the yield test results (drawdown and recovery data), the grouting confirmation, pump specifications and warranty documents, and your water-quality test certificate. These documents matter for insurance purposes, property disclosure if you sell, and diagnosing future problems. Contractors who resist providing them are worth being cautious about from the start.