Water
What a borehole really costs in inland South Africa
A drilling quote is a rate, not a total. Here is what sits between the two, why the depth is the variable that decides everything, and the sequence that stops you buying the wrong pump.
Boreholes
A borehole is the most reliable water source on most inland properties — but it is also the one with the highest variance in outcome. Two properties separated by a fence can sit on entirely different aquifers. One yields 3,000 litres per hour at 40 metres. The other yields 200 litres per hour at 120 metres, or nothing at all. No amount of pre-drilling research eliminates that uncertainty; a hydrogeological survey reduces it.
The first decision is whether to drill at all, and that depends on what a failure costs you relative to what success is worth. The second decision is what to do with the water once you have it — storage, pump selection, pressure, treatment, and backup when load-shedding kills the pump. Those decisions are more predictable than the drilling itself, and they are where most of the ongoing cost and complexity lives.
What determines yield
Yield depends on the aquifer type, the depth to water, and the borehole diameter and casing. In fractured rock — which is common across the Highveld and Bushveld — yield can be high but the borehole must intersect the fracture zone. In sedimentary aquifers yield is more predictable but often lower. Dolomitic ground, which covers a significant portion of Gauteng and the North West, introduces a third problem: the ground itself can be unstable, and drilling can trigger subsidence. A geophysical survey is not optional on dolomite.
Pump and power
Most boreholes use a submersible pump. The pump must be matched to the yield — a pump that draws faster than the aquifer recharges will run dry and burn out. In a load-shedding environment, the pump needs a power source that is independent of the grid: a dedicated solar pump controller feeding directly from panels, a battery backup, or a generator interlock. A borehole that cannot pump during an eight-hour outage is a partial solution, not a complete one.
For the full picture on what drilling and equipping a borehole involves — and what the process looks like from survey to commission — read What a borehole really costs in inland South Africa at water/what-a-borehole-costs.
| Aquifer type | Where common | Yield range | Key risk |
|---|---|---|---|
| Fractured rock | Highveld, Bushveld, Karoo | Very low to very high | Misses fracture zone |
| Sedimentary (alluvial) | River valleys, coastal plains | Low to moderate, consistent | Seasonal variation |
| Dolomitic | Parts of Gauteng, NW Province | Variable | Ground instability, sinkhole risk |
| Weathered basement | Limpopo, parts of Mpumalanga | Low to moderate | Depth to bedrock varies widely |
Rainwater
Rainwater harvesting is the simplest water source to set up and the one most people undersize. The calculation that matters is roof area multiplied by annual rainfall multiplied by a runoff coefficient, compared against daily demand multiplied by the number of days you need to bridge between meaningful rain events. In most inland parts of South Africa, that bridging gap is not the three or four dry weeks that a European system would be sized for — it is a dry season of five to seven months.
That single fact changes the maths completely. A 5,000-litre tank that is adequate in the UK is a week's supply in a dry Highveld winter. Sizing for South African conditions means either very large storage, a supplementary source, or an honest acceptance that rainwater here is a wet-season supplement rather than a primary supply.
First flush and filtration
Roof-harvested water picks up bird droppings, dust, insect debris, and atmospheric pollution. The first flush after a dry spell is the most contaminated. A first-flush diverter — a simple device that routes the first few litres of runoff to waste — removes most of the contamination before it reaches the tank. Without one, the water is usable for irrigation and toilet flushing but requires treatment before it is safe for drinking or cooking.
Gutters must be screened, tanks must be sealed against mosquitoes and light (algae cannot grow in the dark), and the overflow must be directed away from the foundation. These are not optional refinements — they are what separates a rainwater system from a standing water hazard.
The seasonal mismatch
In summer-rainfall regions — which is most of the interior — rain falls when demand from the garden is already partly met by rain on the soil. The dry winter is when irrigation demand peaks, and it is precisely when the tanks are not being refilled. A rainwater system that is not combined with a borehole or municipal top-up will run empty in August on almost any property in Gauteng, Limpopo, or Mpumalanga.
The article Sizing rainwater tanks for inland South Africa rainfall at water/rainwater-harvesting works through the sizing calculation in full, with regional rainfall figures and seasonal profiles.
Greywater
Greywater is wastewater from basins, showers, baths, and laundry — everything except the toilet. In a typical household it is sixty to seventy percent of total wastewater volume, and most of it can be reused for irrigation or toilet flushing without treatment beyond basic filtration. That is water that would otherwise go down the drain, and on a property where water is a constraint it is one of the easier gains to make.
The gain is real but it is bounded. Greywater is not clean water. It contains soap, skin cells, food traces, and — depending on the household — cleaning chemicals that are toxic to plants. It cannot be stored for more than about 24 hours without beginning to smell and harbour pathogens. It cannot be used on vegetables that will be eaten raw without further treatment. Understanding what it can and cannot do is what stops a greywater system from becoming a source of disease or garden damage.
System types
The simplest greywater system is a branched-drain system: gravity-fed from the bathroom, branching through perforated pipes beneath a mulch layer in the garden, with no pumping and no storage. It is cheap, legal for domestic use under current municipal by-laws in most jurisdictions, and effective for subsurface irrigation of trees and shrubs. Its limitation is that it cannot be stored, switched off, or directed to a toilet cistern.
More capable systems — those that filter, buffer, and redirect greywater to toilet cisterns or irrigation on demand — require a pump, a holding tank, and a level of filtration that brings them under the purview of local authority approval in some municipalities. The legal position varies by province and by local authority, and it changed when the National Water Act was amended. Checking with the relevant municipality before installing anything more than a branched-drain system is not bureaucratic caution — it is what prevents a system being ordered removed after installation.
The full treatment of what is legal, what is not, and how the different system types compare is in How a greywater system works and what the law requires at water/greywater-systems.
Wetlands
A constructed wetland is a shallow, planted bed through which wastewater flows slowly enough for plants, bacteria, and sunlight to strip out pollutants before the water returns to the environment or is reused. It is the most biological of the water treatment options, the least mechanically complex, and the one that degrades most gracefully when it is not perfectly maintained. It is also the one that requires the most land area and the most patience — a wetland beds in over two to three growing seasons before it reaches full treatment performance.
On a rural or semi-rural property, a constructed wetland can treat the greywater that a greywater system cannot handle — the kitchen sink, laundry, and anything with higher organic loading — and discharge effluent that is clean enough to use for subsurface irrigation or to recharge a dam. Combined with a greywater system for the simpler waste streams, it can close most of the water loop without a sewage connection or a septic tank.
How the treatment actually works
Water enters the inlet end of the bed, flows horizontally or vertically through a gravel or crushed-stone substrate, and exits at the outlet. Reeds, bulrushes, or other water-tolerant plants grow in the substrate. Their roots create a zone of aerobic activity — where there is oxygen — immediately around them, and an anaerobic zone in the bulk of the substrate between root zones. Different groups of bacteria colonise each zone, and together they handle the range of pollutants in typical domestic wastewater: BOD (biological oxygen demand), suspended solids, nitrogen, and pathogens.
The plants themselves are secondary — the substrate and its bacterial community do most of the work. But the plants are not cosmetic: they oxygenate the root zone, take up nutrients, and provide the structural complexity that the bacterial community needs. A poorly planted or overgrown wetland treats less effectively. Harvesting the above-ground biomass once or twice a year — and removing it, not composting it in place — returns the system to working condition and prevents nutrient accumulation.
Design variables
The critical design parameters are surface area (determined by hydraulic loading rate and treatment target), depth (typically 0.6–0.9 metres for a horizontal-flow system), and inlet/outlet design (which determines flow distribution and prevents short-circuiting). Getting any of these wrong produces a system that treats poorly and smells. Getting them right produces a system that is almost invisible in the landscape and requires an hour or two of maintenance per month.
The detail — including a worked sizing calculation for a four-person household — is in How a constructed wetland actually treats water at water/constructed-wetland.
| Type | Flow direction | Treatment strength | Odour risk | Area required |
|---|---|---|---|---|
| Horizontal subsurface flow (HSSF) | Horizontal through substrate | Good for BOD and solids | Low | Moderate to large |
| Vertical subsurface flow (VSSF) | Vertical, batch-loaded | Better for nitrification | Very low | Smaller than HSSF |
| Free water surface (FWS) | Surface flow, open water | Good for polishing treated effluent | Moderate if overloaded | Largest |
The natural pool
A natural swimming pool replaces chlorine with biology. The water is kept clean by a planted regeneration zone — typically a shallow, planted bay separated from the swimming zone by a submerged wall — through which the pool water circulates continuously. Algae are controlled by the aquatic plants competing for the same nutrients. Pathogens are managed by the same combination of UV light, plant uptake, and bacterial activity that works in a healthy natural water body.
The result, when the system is balanced, is water that is clear, skin-friendly, and free of the chemical load of chlorinated pools. It also does not corrode metal fittings, does not require the chemical management and safety storage that chlorine systems demand, and does not discharge anything to the stormwater system when it is backwashed or drained.
Converting an existing pool
Most natural pool projects in South Africa start as conversions — a chlorine pool that the owner wants to move away from, whether for health reasons, the cost of chemicals, or the complication of chemical management during extended load-shedding. The conversion is not simply a matter of stopping the chlorine and adding plants. The balance of the regeneration zone relative to the swimming zone, the circulation rate, the substrate depth, and the plant selection all determine whether the water clears or turns green.
A converted pool that goes wrong is unswimmable, and restoring it after an algal bloom is harder than establishing the system correctly from the start. The order of operations — how to transition the system without losing water clarity during the changeover — is the most important technical question in a conversion. It is covered in detail in Converting a chlorine pool to a natural swimming pool at water/natural-pool-conversion.
Water consumption
A natural pool uses water differently from a chlorine pool. Evaporation losses are the same. Backwash losses are eliminated. But the regeneration zone is a living plant system, and in a dry climate with low humidity, evapotranspiration from the planted area adds to losses. A natural pool in an inland South African summer may lose marginally more water than a covered chlorine pool of the same surface area. In a water-constrained situation, that is a real consideration — not a reason to reject the option, but a number to account for in the water budget.
Why water is different in South Africa
Almost everything published about water independence online was written for Germany, the UK, Australia, or the American Pacific Northwest — places with year-round rainfall, temperate summers, and functional municipal backup. The advice is often technically sound for those places and quietly wrong for here.
The differences are not marginal. They change the sizing, the sequencing, and sometimes the basic viability of a system.
- Load-shedding breaks pump-dependent systems. A borehole pump, a greywater pump, a pool circulation pump — all of them stop during an outage. Any water system that assumes continuous power availability is not actually independent. Every powered component in a water system needs a credible answer to "what happens during Stage 6?"
- Rainfall is seasonal and concentrated. Most of the interior receives 400–700 mm per year, nearly all of it in summer. Tank sizing based on annual averages is misleading — what matters is the length of the dry season and the peak daily demand during it. A system that is adequate in a wet November can be empty by September.
- Summer temperatures accelerate biological processes. Greywater stored for 24 hours at 35°C is a different material from greywater stored at 15°C. Wetland systems that are undersized for loading work adequately in winter and fail in summer. Natural pools that are balanced in April can tip into an algal bloom by January if the circulation rate is not adjusted.
- Dolomite is widespread and under-mapped. Parts of Gauteng, the North West, and the Northern Cape sit on dolomitic ground where borehole drilling requires geophysical assessment before any equipment touches the ground. Building or drilling on dolomite without a survey is an insurable event waiting to happen.
- Municipal water quality varies and can be unreliable. In areas where municipal supply is inconsistent or the quality of supply has degraded, the assumption that municipal water provides a reliable backup for a rainwater or borehole system is not always safe. A water plan that depends on municipal reliability as its last line of defence needs to be revisited.
- The National Water Act creates obligations, not just rights. Water use in South Africa is regulated. Borehole registration is required above certain yield thresholds. Greywater discharge rules sit with local authorities. Wetland construction near natural watercourses triggers the Act. Knowing what requires authorisation before building is not optional — remediation orders have been issued.
Where most people go wrong
Across the five parts of this subject, the same mistakes recur. They are not obscure errors — they are the predictable results of planning with international references and optimistic assumptions about South African conditions.
- Undersizing storage. The most common single error. A tank that is sized for average monthly rainfall rather than the dry-season gap runs out in August on almost every inland property. The rule of thumb is to size for the longest historical dry spell in your rainfall region, not the average annual figure. That number is almost always larger than it first appears.
- Treating water sources as independent. Borehole, rainwater, greywater, and municipal supply are not four separate systems — they are one water budget. A greywater system that reduces demand on the borehole changes the borehole sizing. A rainwater tank that tops up during summer reduces how hard the borehole works. Planning them separately and then connecting them produces a system full of redundant capacity in some places and dangerous shortfalls in others.
- Ignoring power dependency. A borehole with no solar backup is a grid-dependent water supply. A greywater system with an electric pump is grid-dependent. A pool circulation system that stops for eight hours a day in summer can tip into an algal bloom within a week. Every water system component that requires power needs a power plan, not an assumption.
- Starting with the pool or the wetland. Both are compelling projects and both are relatively late-stage interventions in a water hierarchy. A property that does not yet have reliable primary supply and adequate storage has no business optimising its pool water chemistry. The correct sequence is: primary supply, storage, basic treatment, then enhancement.
- Applying northern-hemisphere product sizing directly. Tank sizing calculators from European suppliers, pump sizing guides from American manufacturers, wetland loading rates from UK design guides — all of them embed assumptions about temperature, rainfall patterns, and evaporation rates that are wrong for the South African interior. Inputs from local references, or manually corrected for local conditions, are necessary.
Where to start
- Audit your current water use before touching anything. Know your monthly municipal consumption, your peak daily demand, and where the bulk of it goes. Irrigation and toilet flushing are typically the two largest uses, and they are also the two that are easiest to substitute with alternative sources.
- Check what is under the ground before you drill. Commission a hydrogeological survey or at minimum a desktop assessment. On dolomitic ground, a geophysical survey is not optional. Talk to neighbours who have drilled — local yield and depth data is more useful than any desktop model.
- Resolve primary supply first. Whether that is a borehole, a municipal connection with storage backup, or harvested rainwater, establish a reliable source before investing in treatment or enhancement. A greywater system that reduces demand by 30% is useful; a greywater system that is the only source is a crisis.
- Size storage for the dry season, not the average month. Use the articles on borehole and rainwater sizing — the calculations are worked through in full there — and apply the dry-season figure rather than the annual average.
- Plan for power failure from the start. Every pump and circulation system needs a solar backup, a gravity alternative, or a manual fallback. Retrofitting this is always more expensive than designing it in.
- Read the relevant deep articles before buying anything. The five articles in this pillar — on boreholes, rainwater sizing, greywater law, wetland construction, and natural pool conversion — contain the detail that determines whether a system works or has to be rebuilt. The pillar orients; the articles decide.
