Why Boreholes Fail (and How to Avoid It)

A borehole is a long-term infrastructure investment. Done right, it can supply your household with water for 20 years or more. Done wrong, it becomes an expensive hole in the ground. The frustrating part is that most failures are entirely predictable — and avoidable — if you know what to look for before the drilling rig arrives.

Here is a plain breakdown of why boreholes fail and what you can do about each cause.

1. Poor Site Selection

Groundwater in Johannesburg does not distribute evenly. The geology across the Highveld varies considerably — dolomite areas around Krugersdorp and Centurion behave very differently from the harder granite and quartzite formations further east. Drilling in the wrong spot means either a dry hole, low yield, or water that is too mineralised to use without expensive treatment.

What to do: insist on a hydrogeological assessment before drilling. A desktop study using existing borehole logs and geological maps is the minimum; a geophysical survey (typically resistivity or electromagnetic) gives you a much higher probability of hitting a productive fracture zone. This costs money upfront but is a fraction of the cost of a failed borehole.

2. Inadequate or Wrong Casing

Casing is the lining that protects the borehole from collapse and prevents surface water — runoff, sewage, garden chemicals — from contaminating the aquifer. Skimping on casing depth or material is one of the most common and most damaging shortcuts in the industry.

If the casing does not extend deep enough through the unstable upper soil and weathered rock zones, the borehole wall can collapse, blocking or destroying the pump. If the casing seal at surface is poor, contaminated surface water bypasses the natural filtration of the soil profile and enters directly into your water supply. This is a health risk, not just a mechanical one — SANS 241 (2024 edition) sets the drinking-water quality standard your borehole water should meet, and a compromised casing makes compliance very difficult.

For a thorough explanation of casing types, depths and materials, see our guide to borehole casing explained. It covers everything from steel versus uPVC to grout sealing requirements.

3. Oversized or Undersized Pumps

The pump is the component that fails most often, and the most common reason is a mismatch between pump capacity and the borehole’s sustainable yield.

An oversized pump draws water faster than the aquifer can recharge. This is called overpumping. It drops the water level below the pump intake, causing the pump to run dry. Running dry generates heat, destroys the motor windings, and can score the pump casing beyond repair — all within minutes of the water level dropping. Repeated dry-running is the single largest cause of premature pump failure.

An undersized pump, by contrast, cannot deliver the flow rate you need, leaving you with inadequate pressure or a storage tank that never fills properly.

The solution is a proper yield test after drilling. A step-drawdown test or extended constant-rate test tells you the borehole’s sustainable yield so your installer can size the pump correctly. Do not let anyone skip this step. Borehole pumps typically cost R15,000–R35,000 installed; replacing one prematurely because it was the wrong size from the start is an avoidable expense.

4. No Maintenance Programme

A borehole that works perfectly on installation day will not maintain itself. Without regular attention, small problems compound into expensive ones.

The most common maintenance failures are:

• Neglected pump servicing — bearings wear, motor insulation degrades, and submersible cable connectors corrode in the wet downhole environment
• No water quality testing — aquifer chemistry can change, bacterial contamination can develop, and you may not know until someone gets ill
• Casing inspection skipped — surface seals can crack, allowing ingress over time
• Borehole left idle for extended periods — stagnant water in a sealed system can harbour bacteria and cause pump seizure on restart

For a practical checklist covering annual, bi-annual and five-yearly tasks, our borehole maintenance schedule sets out exactly what to inspect and when. Following it consistently is the cheapest form of borehole insurance available.

If you are still at the planning stage, getting competing quotes from vetted drillers is the simplest way to ensure you are not cutting corners on casing or pump sizing. Compare 3 free quotes — vetted installers, no obligation.

5. Drilling Into Problem Geology Without Knowing It

Johannesburg sits partly over dolomitic ground. Dolomite dissolves over time, forming voids and sinkholes — a risk that goes well beyond borehole performance. Drilling into active dolomite without a geotechnical risk assessment can destabilise the ground around the borehole. Even outside dolomite zones, drilling through fractured rock without proper grouting can create a hydraulic connection between shallow contaminated zones and deeper clean aquifers, permanently compromising water quality in the area.

The Department of Water and Sanitation (DWS) has registration requirements for boreholes used for purposes beyond domestic household supply, and best practice — regardless of registration status — is to follow DWS guidelines on construction standards. Reputable drillers will be aware of these and build compliance into their methodology. Ask specifically whether your contractor follows DWS construction guidelines.

6. Using Unregistered or Unqualified Drillers

The drilling industry has a lower barrier to entry than most homeowners assume. Not every company that shows up with a rig has the experience to assess your geology, specify the right casing, conduct a yield test and size the pump correctly. Price-shopping on the day rate alone, without checking credentials, references and the quality of their site investigation methodology, is how many homeowners end up with a failed borehole.

When evaluating contractors, ask for:

• Proof of the geophysical survey method they use for site selection
• Their standard casing depth and material specification for your area
• Whether a yield test is included or an optional extra
• References from installations in your suburb or geological zone

Our main borehole drilling guide covers what to look for in a contractor, typical full-system costs (which run R40,000–R150,000 depending on depth, pump specification and storage requirements), and the questions to ask before signing anything.

Choosing between contractors is easier when you can compare their scope of work side by side. Get your free quotes here — no obligation, no hard sell.

What the Numbers Tell You

Failure cause	Typical point of failure	Preventable?
Poor site selection	Dry or low-yield hole post-drilling	Yes — geophysical survey before drilling
Inadequate casing	Collapse or contamination within 1–5 years	Yes — specify correct depth and material upfront
Wrong pump size	Motor burnout, often within 1–3 years	Yes — yield test before pump selection
No maintenance	Gradual degradation, often unnoticed	Yes — scheduled servicing programme
Dolomite / geology risk	Structural or water-quality failure	Yes — geotechnical assessment required
Unqualified driller	Multiple of the above	Yes — vet credentials before drilling

The Short Version

Borehole failures are rarely mysterious. They almost always trace back to corners cut at the start — in site assessment, casing specification, pump sizing, or contractor selection — or to maintenance that was promised but never delivered. The remedies are straightforward: invest in a proper hydrogeological assessment, insist on adequate casing, do not skip the yield test, and put a maintenance schedule in writing before the rig leaves your property. None of this is complicated. It just requires asking the right questions before you commit.