Boreholes lose performance over time. The flow that comfortably ran the irrigation ten years ago now struggles, the pump runs longer for less water, and the obvious conclusion is that the borehole is finished.
Often it is not. A large proportion of declining boreholes are not running out of water - they are becoming harder for water to enter. Sediment fills the bottom, mineral deposits encrust the screen, bacterial growth clogs the gravel pack, and the borehole slowly throttles itself. Rehabilitation is the process of reversing that where it can be reversed.
It is worth being clear about the ceiling. Rehabilitation can restore capacity that has been lost to blockage. It cannot create more groundwater than the aquifer holds, and it cannot rebuild a borehole that has failed structurally.
Losing yield on an older borehole? An inspection tells you whether it is recoverable.
Request a Rehabilitation AssessmentWhy Boreholes Decline
| Cause | What happens | How recoverable it usually is |
|---|---|---|
| Sediment accumulation | Fine material settles at the base over years, gradually filling the hole from the bottom up and eventually covering the screened interval or reaching the pump. | Generally very recoverable by desilting. |
| Mineral encrustation | Dissolved minerals - commonly iron and carbonates - precipitate on and around the screen, progressively narrowing the openings water passes through. | Often substantially recoverable through mechanical and chemical redevelopment. |
| Biofouling | Naturally occurring bacteria form biofilm and slime around the screen and gravel pack, frequently in combination with iron deposits. | Frequently recoverable, though it can recur and may need periodic treatment. |
| Gravel pack clogging | Fine formation material migrates into the pack, reducing how easily water reaches the screen. | Partially recoverable through surging and redevelopment. |
| Inadequate original development | The borehole was never properly developed after drilling, so fines were left in place and it never achieved its potential. | Often responds well, sometimes producing better yield than the borehole ever had. |
| Casing or screen damage | Corroded, split, collapsed or perforated casing, which can also let sand in. | Limited. May be repairable by lining in some cases, but often not economically recoverable. |
| Genuine aquifer decline | Regional water level drop from drought or over-abstraction across an area. | Not recoverable by rehabilitation, because nothing is blocked. |
Note the last row. If the aquifer level has fallen, the borehole is working correctly and cleaning it will change nothing. Distinguishing that from blockage is the first job of an assessment, and it is why yield testing and water level measurement come before any work is proposed.
Assessment Comes First
Rehabilitation without diagnosis is expensive guesswork. A proper assessment establishes what has actually changed:
- 1Review the history. Original drilling and construction details, the commissioning yield, and how performance has changed over what period.
- 2Measure current water levels - standing and pumping - and compare against the original figures.
- 3Re-test yield to quantify the decline objectively rather than by impression, and to establish current specific capacity.
- 4Compare specific capacity. If the water level is unchanged but yield per unit of drawdown has fallen, the borehole is blocked. If the water level itself has dropped, the aquifer has changed and cleaning will not help.
- 5Remove the pump and inspect it. Its condition tells you a great deal about what has been happening downhole.
- 6Run a downhole camera where warranted. This is the step that removes the guesswork - you see the casing condition, the screen, encrustation, sediment level and any damage directly.
- 7Sound the depth and compare against the original drilled depth to quantify sediment build-up.
- 8Decide whether rehabilitation is justified, and be prepared for the answer to be no.
The camera earns its cost. A downhole inspection is the difference between treating a borehole and guessing at it. It distinguishes encrustation from collapse, shows whether casing is intact, and often reveals that the problem is somewhere other than assumed. It also gives you a defensible basis for deciding whether to spend on rehabilitation or on a new borehole.
Rehabilitation Methods
Most programmes combine several techniques, because each addresses a different part of the problem and they work better together than alone.
Mechanical
- Desilting - removing accumulated sediment from the base of the borehole to recover lost depth and clear the screened interval
- Brushing - running a wire brush tool over the screen to physically remove deposits from the openings
- Surging - moving a surge block up and down to force water back and forth through the screen and gravel pack, dislodging fines and breaking up deposits
- High-pressure jetting - directing jets at the screen to clean openings and agitate the pack behind them
- Airlifting - using compressed air to lift loosened material out of the hole, usually after each stage of mechanical work
Chemical
Where deposits are mineral or biological rather than simply loose sediment, chemical treatment may be used alongside mechanical work - acids to dissolve carbonate and iron encrustation, or disinfection to address bacterial fouling. Chemical treatment needs care: the right chemistry for the deposit, adequate contact time, thorough neutralisation and removal afterwards, and proper handling of what comes out of the hole. It is not a routine first step, and the borehole should be re-sampled afterwards before the water is used.
Redevelopment
After cleaning, the borehole is redeveloped much as a new borehole is - pumping and surging until the water runs clear and the formation around the screen is stable. This is what converts cleaning into recovered yield, and it is the stage most often cut short.
Get an assessment that measures the decline before anyone proposes a treatment.
Get a Rehabilitation QuoteProving It Worked
Rehabilitation should be measured, not asserted. The borehole is re-tested afterwards and compared against the pre-rehabilitation figures:
- Yield at a given drawdown, before and after
- Specific capacity, before and after - the clearest single measure of improvement
- Recovered depth, from sounding against the original drilled depth
- Sand content in the discharge, which should be reduced or eliminated
- A water sample after any chemical treatment, before the water goes back into use
Ask for these comparisons in writing. A rehabilitation that produces no measurable change in specific capacity has not achieved anything, and you should know that rather than assume improvement.
Rehabilitate or Redrill?
The honest answer depends on what the assessment finds, and there are cases where drilling a new borehole is the better use of money:
| Points toward rehabilitation | Points toward a new borehole |
|---|---|
| Water level unchanged but specific capacity has fallen | Water level itself has dropped substantially - the aquifer, not the borehole |
| Casing and screen intact on camera inspection | Casing collapsed, badly corroded or perforated |
| Significant sediment accumulation measured | Borehole silted to the point that the screened interval is unrecoverable |
| Encrustation or biofilm visible on the screen | Structural damage that cannot be economically lined or repaired |
| The borehole performed well historically | The borehole never performed well, suggesting it was poorly sited or constructed |
| Water quality remains acceptable | Water quality has deteriorated in a way rehabilitation cannot address |
Where rehabilitation is viable it is usually the more economical route, since it avoids mobilising a rig, new casing and a new pump installation. Where the assessment points the other way, the borehole drilling page covers what a new hole involves, and a water survey would be the sensible first step.
Keeping the Gains
Rehabilitation restores a borehole; it does not immunise it. The same processes that caused the decline continue, and how the borehole is operated affects how quickly they return:
- Operate within the sustainable abstraction rate from the post-rehabilitation test rather than the original one
- Avoid heavy over-pumping, which accelerates fines migration and encrustation
- Keep servicing records so the next decline is spotted early
- Monitor flow and water level periodically against the post-rehabilitation baseline
- Where biofouling was the cause, expect it to recur and plan periodic treatment rather than waiting for failure
- Address any sand at source, because it will otherwise keep filling the hole and wearing pumps
Related Borehole Services
Where the assessment shows the borehole has failed structurally rather than simply become blocked, a new hole is the better use of money - Borehole Drilling Cape Town covers what drilling a replacement involves and what it should cost.
What Borehole Rehabilitation Costs
The comparison that matters is against redrilling. Where the assessment shows recoverable blockage, rehabilitation is usually a fraction of a new borehole. Where it shows structural failure or a dropped aquifer level, it is money wasted - which is why assessment comes first.
| Item | Indicative range | What moves it |
|---|---|---|
| Assessment and re-test | R4,000 – R15,000 | Comparing current specific capacity against the original figures. Establishes whether rehabilitation is even viable. |
| Downhole camera inspection | R2,500 – R8,000 | The step that removes the guesswork. Depth and whether the pump must come out first. |
| Desilting and airlifting | R5,000 – R20,000 | How much sediment has accumulated and how deep the borehole is. |
| Mechanical brushing, surging and redevelopment | R8,000 – R35,000 | Screen length, severity of encrustation and how many passes are needed. |
| Chemical treatment | R6,000 – R25,000 | Deposit type, contact time, and safe handling and disposal of what comes out. |
| Post-rehabilitation yield test | R4,000 – R12,000 | Proves whether it worked. Insist on the before-and-after specific capacity comparison. |
| Full programme, typical domestic borehole | R20,000 – R60,000 | Against R70,000–R150,000+ to redrill on a hard-rock site. |
These are indicative ranges, not a quotation. They are compiled from published South African supplier and contractor pricing to give you a starting point for budgeting. They are not our rate card, and no figure here is a commitment.
Treat them as a broad guide only. Published borehole pricing in South Africa varies enormously - different 2026 guides quote per-metre drilling rates for the same province that differ by a factor of three - because depth, geology, access, specification, distance and fuel costs all move the number. Depth in particular is not known until the hole is finished. Figures generally exclude VAT unless noted, and change over time. Only an itemised written quote against your actual site means anything.
Borehole Rehabilitation FAQs
Can an old borehole be restored?
Frequently, yes - provided the decline is caused by blockage rather than by the aquifer. Sediment accumulation, mineral encrustation on the screen, biofouling and gravel pack clogging are all common causes of lost yield, and all are at least partly recoverable.
What rehabilitation cannot do is create water that is not there. If the regional water level has dropped, the borehole is working correctly and cleaning it will change nothing. An assessment establishes which situation applies before any work is proposed.
How do I know if my borehole needs rehabilitation or a new pump?
By measuring, not guessing. Re-test the borehole and compare specific capacity - yield per unit of drawdown - against the original figures. If specific capacity has fallen while the water level is roughly unchanged, the borehole has become restricted and rehabilitation is indicated.
If the borehole still tests close to its original performance, the problem is in the equipment and belongs on the repairs side. This is exactly why keeping the original yield test report matters.
What does a downhole camera inspection show?
It shows the inside of the borehole directly - casing condition, joints, the screened interval, encrustation on the screen openings, sediment level at the base, and any splits, corrosion or collapse.
It is the step that converts a rehabilitation proposal from a theory into a plan, because it distinguishes a blocked but sound borehole from one that has failed structurally. It also tells you whether the problem is where everyone assumed it was.
Is rehabilitation cheaper than drilling a new borehole?
Where it is viable, usually yes, because it avoids mobilising a drilling rig, buying new casing and installing a complete new system. It also avoids the risk that a new hole does not perform as well as hoped.
But it is only worth doing where the assessment shows recoverable blockage. Spending on rehabilitation of a structurally failed borehole, or one where the aquifer level has dropped, is money wasted - and a good assessment will tell you that plainly.
How long does borehole rehabilitation take?
It depends on what is being done. Removing the pump, desilting and airlifting is a shorter operation than a full programme involving camera inspection, mechanical brushing and surging, chemical treatment with contact time, and full redevelopment.
Allow for the borehole being out of service for the duration, plus re-testing afterwards. Where chemical treatment is used, the water should also be re-sampled before it goes back into normal use.
Will rehabilitation restore my borehole to its original yield?
Not necessarily, and nobody should promise it will. Rehabilitation recovers capacity lost to blockage, so the realistic ceiling is what the borehole could produce if the screen and formation around it were clear.
Some boreholes recover most of their original performance; others recover a useful but partial amount; occasionally a borehole that was never properly developed in the first place performs better afterwards than it ever did. The honest answer before the work is a range rather than a figure.
Is chemical treatment safe for my borehole and the water?
Used correctly it is a well-established technique, but it needs care. The chemistry has to match the deposit, contact time has to be adequate, and everything must be properly neutralised and removed from the borehole afterwards, with the recovered fluid handled responsibly.
The borehole should be thoroughly redeveloped and the water re-sampled before it goes back into use, particularly where the water is used domestically. It is not a routine first step - mechanical methods usually come first.
How often does a borehole need rehabilitation?
There is no set interval, because it depends on the water chemistry, the formation, how the borehole was constructed and how hard it is pumped. Some boreholes run for decades without needing it; others with aggressive iron chemistry or persistent biofouling need periodic attention.
Rather than working to a schedule, monitor performance. Recording flow and water level periodically against the baseline from the last yield test will tell you when decline is setting in, well before it becomes a problem.
BEFORE YOU DRILL A NEW ONE.
Rehabilitation often recovers a declining borehole for far less than redrilling.
Request an AssessmentRequest a Borehole Rehabilitation Assessment
Tell us the borehole's age, depth and how performance has changed.
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