Borehole Filtration Systems
Cape Town

There is no such thing as a standard borehole filtration system, because there is no such thing as standard borehole water. Two properties in the same suburb can produce water with entirely different chemistry, and a system that solves one property's problem may do nothing at all for the other's.

This is why filtration starts with a laboratory analysis rather than a catalogue. The analysis tells you what is actually in the water; the intended use tells you what needs to come out. Everything else follows from those two things.

Match the Treatment to the Use

Before choosing equipment, be clear about what the water has to be good enough for. The standard is set by the application, and over-treating is as wasteful as under-treating:

Use	What usually matters
Garden and lawn irrigation	Sediment removal to protect emitters and sprinklers. Salinity and sodium matter for sensitive plants. Iron staining on paving and walls is a common complaint. Microbiological quality is generally less critical.
Drip and micro-irrigation	Fine sediment filtration is essential - drippers block easily. Iron and biofouling are significant because they build up inside emitters over time.
Toilet flushing and laundry	Sediment and iron. Iron staining on laundry and cisterns is the usual driver for treatment here.
General household use, not drinking	Sediment, iron and manganese, and hardness if scaling in the geyser and appliances is a concern.
Drinking and food preparation	The full picture - microbiological safety first, then nitrate, metals, and any parameter exceeding drinking water limits. This sets the highest bar.
Pool top-up	Iron and manganese in particular, since they stain pool surfaces and interfere with pool chemistry. Hardness matters for scaling.
Commercial and process water	Depends entirely on the process. Hardness for boilers and heat exchangers, sediment for equipment protection, and specific parameters as the application dictates.

Treatment Options and What Each One Addresses

Filtration is usually a sequence rather than a single device, with each stage handling a different problem and protecting the stage after it.

Sediment and particulate removal

• Cyclone or centrifugal sand separators - remove heavier sand ahead of everything else. Worth fitting where any sand is present, because sand destroys downstream equipment.
• Multimedia or sand filters - backwashing filters that handle larger volumes and higher sediment loads without constant cartridge changes.
• Cartridge filters - available in a range of micron ratings, effective and inexpensive, but they need regular replacement and are best used as a polishing stage rather than as the primary defence against heavy sediment.
• Disc filters - common on irrigation systems, easy to clean and well suited to protecting emitters.

Persistent sand is worth investigating rather than simply filtering. It usually indicates a screen, gravel pack or development problem in the borehole itself, which rehabilitation may address at source.

Iron and manganese

The most common treatment requirement on local groundwater, and the cause of most of the staining complaints. Both dissolve invisibly in water that arrives clear, then oxidise on contact with air and deposit as reddish-brown (iron) or black (manganese) staining.

Treatment is generally a two-stage process: oxidise the dissolved metal into a solid particle, then filter that particle out. The oxidation method and filter media are chosen from the concentrations in your analysis, the pH, and whether manganese is present alongside iron - manganese is more difficult and needs a higher pH to oxidise properly.

Hardness

Calcium and magnesium cause scaling in geysers, kettles, pipework, shower heads and appliances. Ion exchange softening is the established treatment where the use justifies it. Softening adds sodium to the water and requires periodic salt, so it is usually applied to the hot water and appliance circuits rather than to everything.

Taste, odour and organics

Activated carbon addresses taste and odour issues and some organic compounds. It is a polishing stage, fitted after sediment and iron removal, and the media needs periodic replacement because it becomes exhausted rather than clogged.

Disinfection

Where microbiological contamination is present and the water is used domestically, disinfection is needed. Ultraviolet treatment is common for point-of-entry use - it needs clear water to work, so it goes last in the sequence after sediment and iron have been removed. Chlorination is an alternative, particularly where a storage tank provides contact time.

Disinfection treats the water. It does not close the pathway that let contamination into the borehole, and that pathway - a defective sanitary seal, damaged casing, or a nearby septic source - should be found and fixed rather than permanently filtered around.

Membrane treatment

Reverse osmosis reduces total dissolved solids and addresses salinity, and is the route where conductivity, chloride and sodium are high. It is the most expensive option, requires thorough pre-treatment to protect the membranes, produces a reject stream that has to go somewhere, and reduces the volume of usable water. It is generally applied to drinking water at a point of use rather than to a whole property, unless the application genuinely requires it.

How a Filtration System Is Specified

1. 1Analyse the raw water, sampled at the borehole discharge before any storage or existing treatment.
2. 2Define the intended use and therefore the standard the treated water must meet.
3. 3Establish the flow rate the system must handle. Treatment equipment is rated for flow, and an undersized unit simply passes untreated water through at peak demand.
4. 4Select the treatment sequence, stage by stage, from the analysis results.
5. 5Check pH compatibility. Several processes - particularly manganese oxidation - only work within a pH range, and pH correction may be needed ahead of them.
6. 6Design for servicing. Isolation valves either side of each stage, accessible housings, sample points and space to work.
7. 7Plan backwash and waste. Backwashing filters discharge periodically and that water needs a route away.
8. 8Commission and verify by re-testing the treated water, confirming the system does what it was specified to do.

That last step is the one most often skipped, and it is the only proof the system works. Re-test after commissioning.

Where Filtration Sits in the System

Treatment placement depends on the system layout. In a tank-based system, primary treatment is usually placed between the borehole and the tank so that stored water is already treated, with any final polishing after the booster pump. In a direct pressure system, treatment sits after the pump and before distribution.

Where only some water needs high-grade treatment, splitting the system is often the sensible economy - treat everything to a basic standard for irrigation and general use, and add point-of-use treatment for drinking water only. Treating an entire property's water to drinking standard when most of it goes on the garden is an expensive way to water a lawn.

Running Costs and Servicing

Filtration is not a fit-and-forget purchase, and the ongoing commitment should be part of the buying decision:

• Cartridge filters need regular replacement, more often where sediment is heavy
• Backwashing filters use water each time they regenerate
• Softeners need salt on an ongoing basis
• Carbon media becomes exhausted and needs periodic replacement
• UV lamps have a service life and lose output before they fail, so they need replacing on schedule rather than on failure
• Membranes need replacement and are sensitive to inadequate pre-treatment
• The treated water should be re-tested periodically to confirm the system is still performing

A neglected filtration system can be worse than none at all - an exhausted carbon filter or a fouled UV unit gives the appearance of treatment without the substance. Filter servicing usually runs on a shorter cycle than general borehole maintenance.

What Affects Filtration System Cost

• How many treatment stages the analysis actually requires
• The flow rate the system has to handle, since equipment is sized by flow
• Whether backwashing filters or cartridge filters are used - higher upfront cost against lower ongoing consumables
• Whether disinfection is needed, and by what method
• Whether membrane treatment is required, which is a significant step up in cost and complexity
• Whether pH correction is needed ahead of other processes
• Whether treatment is whole-property or point-of-use for drinking water only
• Installation conditions - space, plumbing modifications, drainage for backwash, and electrical supply

Related Borehole Services

Some treatment problems are really construction problems - persistent sand and surface contamination both point back to screening and sealing. Borehole Drilling Cape Town explains how a borehole should be built so filtration has less work to do.

What Borehole Filtration Costs

Treatment cost follows your water analysis and nothing else, so this is the least predictable scope in a borehole project. The ranges below are per stage - most systems are a sequence of two or three, and few properties need all of them.

Item	Indicative range	What moves it
Cyclone or sand separator	R1,500 – R6,000	Flow rate. Worth fitting wherever any sand is present, ahead of everything else.
Cartridge filter housings and media	R800 – R4,500	Number of stages and micron rating. Cheap upfront, ongoing cartridge cost.
Multimedia or backwashing sand filter	R6,000 – R25,000	Vessel size for the flow rate, and whether the valve is manual or automatic.
Iron and manganese removal	R8,000 – R35,000	The most common local requirement. Concentrations, pH and whether manganese is present alongside iron.
Ion exchange softener	R7,000 – R30,000	Hardness level and flow rate. Ongoing salt cost.
UV disinfection	R3,500 – R15,000	Flow rate. Needs clear water, so it goes last in the sequence.
Reverse osmosis	R12,000 – R80,000+	Point-of-use is far cheaper than whole-property. Needs pre-treatment and produces a reject stream.
Typical whole-house system	R15,000 – R60,000	Sediment plus iron removal plus disinfection, sized for a domestic flow rate.

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