Why Boreholes Deteriorate
Every borehole has a finite lifespan, but the rate of deterioration depends heavily on the geology, water chemistry, pump selection, and maintenance regime. Most boreholes in Southern Africa are designed for a 20–30 year service life, but without proper monitoring, many fail in under 10 years.
The good news is that deterioration rarely happens overnight. There are clear, observable warning signs that give you months — sometimes years — to intervene before the situation becomes critical.
Sign 1: Declining Water Yield
If your borehole is producing noticeably less water than when it was first commissioned, this is the most common early warning sign. Declining yield can indicate aquifer depletion, screen blockage by mineral encrustation, or biofouling from iron bacteria.
A yield drop of more than 15–20% from the original test pump data warrants investigation. Start by comparing current pump run times with historical data. If the pump runs longer to fill the same tank, the yield has dropped.
Sign 2: Sand or Sediment in the Water
Clean boreholes produce clear water. If you're seeing sand, grit, or fine sediment at the tap or in your storage tanks, something is wrong underground. Common causes include screen deterioration, casing corrosion, or gravel pack failure.
Sand production is particularly damaging because it accelerates pump impeller wear, leading to a cascading failure that destroys expensive equipment.
"A borehole producing sand is a borehole on borrowed time. Every grain of sediment is wearing down your pump and widening the cracks in your casing."
Sign 3: Discoloured or Odorous Water
Changes in water colour — particularly reddish-brown or black tints — usually indicate iron or manganese oxidation, or bacterial contamination within the borehole. A sulphurous (rotten egg) smell points to hydrogen sulphide gas, often produced by sulphate-reducing bacteria.
These issues often develop gradually. Regular water quality testing — at least twice a year — will catch changes that are invisible in day-to-day use.
Sign 4: Pump Cycling or Air Locks
If your pump is switching on and off rapidly, or you're getting air bursts from the delivery pipe, the water level may be dropping below the pump intake. This "pump cycling" causes severe motor stress, overheating, and premature failure.
Common causes include over-pumping (extracting more than the aquifer can replenish), a lowered static water level due to drought, or screen blockage restricting inflow.
Sign 5: Increasing Energy Consumption
A borehole pump working harder to deliver the same volume of water will consume more electricity. If your energy bills have crept up without an obvious explanation, the pump may be losing efficiency due to impeller wear, or the dynamic water level may be dropping, requiring more head pressure.
Key Takeaway
Rehabilitating a borehole typically costs 20–30% of drilling a new one. The earlier you intervene, the more options you have — and the less it costs. Don't wait for complete failure.
What Rehabilitation Involves
Borehole rehabilitation typically includes a CCTV inspection to assess the casing and screen condition, followed by mechanical or chemical cleaning (airlifting, jetting, or acid treatment). If the screen or casing is damaged, partial relining may be required.
After cleaning, a step-drawdown test confirms the recovered yield, and water quality samples verify that the treatment has been effective. The entire process usually takes 2–5 days depending on the borehole depth and condition.
