For many borehole owners, the first indication that something is not quite right does not arrive as a sudden mechanical failure or a complete loss of pressure. Instead, it presents itself quietly, almost subtly, in ways that are easy to overlook at first.
The toilet bowl begins to show staining that was never there before.
Water drawn into a white basin carries a faint yellow tint. There may be a slight change in smell, something unfamiliar but not immediately alarming. Tea tastes different. A glass of water, when held up to the light, appears slightly cloudy rather than perfectly clear.
Individually, these changes may seem minor. Together, they begin to form a pattern.
In many cases, they are dismissed. It is assumed that the issue is temporary, or that a simple filter replacement will resolve it. However, changes in borehole water quality are rarely random.
They are indicators — subtle signals that reflect changes occurring below ground, within the borehole itself, or somewhere within the broader system connected to it.
Understanding these signals removes the need for guesswork and, importantly, prevents unnecessary expenditure on solutions that do not address the root cause.
Why Borehole Water Quality Changes Over Time
A borehole draws water from a subsurface environment that is constantly evolving. Groundwater moves slowly through layers of soil, rock formations and fractures, interacting with minerals and materials along the way. This environment is not fixed.
Rainfall patterns shift from season to season. Water tables rise during wet periods and decline during drought. Nearby land use changes, sometimes gradually and sometimes quite rapidly. Septic systems age. Agricultural practices intensify. Even the components of the borehole itself — casing, pipes and fittings — begin to change over time.
These factors combine to influence both the chemistry and behaviour of the water.
Over the course of years, it is entirely normal for borehole water to change. What matters is not that change occurs, but whether it is understood and managed appropriately.
This is where periodic laboratory testing becomes essential. By testing water against benchmarks such as SANS 241, borehole owners gain an objective understanding of what is happening, rather than relying on taste, smell or appearance alone.
When Water Turns Brown, Yellow or Rust-Coloured
One of the most common concerns among borehole users is the sudden appearance of discoloured water, often described as brown, yellow or rusty.
At first glance, this can appear alarming, and it is often interpreted as the borehole becoming “dirty.” In reality, the cause is usually more specific.
In many parts of South Africa, groundwater contains naturally occurring dissolved iron. While this iron may be invisible when the water is underground, it reacts as soon as it is exposed to oxygen at the surface. The result is a visible transformation — clear water turning into a rusty or orange-toned liquid once it enters tanks or pipes.
In other cases, the issue may lie in the physical structure of the borehole. Fine sediment can enter the system if the screen or gravel pack begins to fail, or if the surrounding formation is disturbed. Older boreholes with steel casings may also introduce discolouration as corrosion develops over time.
There are also instances where heavy pumping or seasonal shifts in the water table disturb the aquifer, bringing suspended material into the flow.
While iron-rich water is not always a direct health concern, it is a quality issue that often requires proper filtration. More importantly, a sudden or worsening change in colour may indicate that the issue extends beyond chemistry and into the physical integrity of the borehole itself.
When Water Develops an Unusual Smell
Changes in smell tend to raise concern more quickly, and rightly so.
A distinct “rotten egg” odour is typically associated with hydrogen sulphide gas, which forms in low-oxygen environments through bacterial activity. This is relatively common in certain groundwater conditions and, while unpleasant, is often manageable with appropriate treatment.
More concerning are smells that resemble sewage or decaying organic material. These suggest the possibility of microbiological contamination, often linked to surface sources such as septic systems, livestock activity or runoff entering the groundwater system.
There are also cases where organic material enters the borehole directly, usually as a result of poor sealing at the surface or incorrect positioning.
It is worth noting that stagnant water in storage tanks or pipework can also produce odours, even when the borehole itself is not the source.
Distinguishing between these possibilities requires more than observation. It requires testing and, where necessary, inspection of the system.
When Water Appears Cloudy or Milky
Cloudiness in borehole water, often referred to as turbidity, can present in different ways, each pointing to a different underlying cause.
In some cases, the water contains fine sand or silt. This typically settles if left undisturbed, forming a visible layer at the bottom of a container. This type of turbidity usually indicates that material is entering through the borehole screen or that the surrounding formation has been disturbed, often due to over-pumping or structural issues.
In other cases, the cloudiness is caused by air. Tiny bubbles suspended in the water give it a milky appearance, but this clears from the bottom upwards as the air dissipates.
The distinction is important.
Air-related turbidity is generally a system or pressure issue and is less serious. Sand, however, is a warning sign. Over time, it causes significant wear on pumps and can indicate a deeper problem with the borehole’s construction or condition.
When Taste Begins to Change
Taste is often the last aspect people trust, yet it can be one of the most telling.
A shift toward a salty, metallic or bitter taste is usually linked to changes in dissolved minerals. Groundwater naturally carries a range of dissolved substances, and variations in flow or source can alter this balance.
In coastal areas or certain inland formations, salinity can increase over time. In other cases, elevated levels of iron, manganese or total dissolved solids may influence taste.
These changes are rarely detectable through observation alone. They require laboratory analysis to determine exactly what is present in the water and whether it remains within acceptable limits.
Knowing When to Act
There are certain situations where delay is not advisable.
If water begins to smell strongly of sewage, becomes suddenly and heavily discoloured, or shows a marked change in taste, testing should be arranged without hesitation. The same applies where there is persistent cloudiness, rapid staining, or any indication that the water may be affecting health.
In these cases, assumptions are not only unhelpful, they can be dangerous.
Testing provides clarity. It replaces uncertainty with measurable data and allows decisions to be made on a solid foundation.
What Can Be Treated and What Requires Deeper Investigation
Not all water quality issues carry the same weight.
Some are relatively straightforward to address. Iron staining, mild sulphur odours and certain mineral-related taste issues can often be managed effectively through filtration and treatment systems.
Others point to more fundamental concerns.
Persistent sand in the water, recurring contamination, or rapid changes following rainfall often indicate structural issues within the borehole or problems with its interaction with the surrounding environment. These cannot be resolved through filtration alone. They require inspection, and in some cases, rehabilitation.
Understanding the difference between these categories is essential. It prevents the common mistake of treating symptoms while the underlying cause remains unaddressed.
Diagnostic table: symptom → likely cause → action
| Symptom | Likely Cause | What It Means | Action |
| Brown/yellow staining | Iron oxidation | Common in groundwater | Test + iron filter |
| Rotten egg smell | Hydrogen sulphide | Bacterial activity | Test + treatment |
| Sewage smell | Contamination | Serious risk | Immediate testing |
| Cloudy water (settles) | Sand/silt | Screen/gravel issue | Borehole inspection |
| Cloudy water (clears) | Air in system | Pressure issue | Check pressure system |
| Salty/metallic taste | High minerals/TDS | Geological | Test + treatment |
| Sudden changes after rain | Runoff contamination | Positioning/sealing issue | Inspect borehole head |
Borehole water does not change randomly.
Colour, smell, and taste are messages from the system. The correct response is not guesswork or repeated filter changes, but understanding the cause through testing and inspection.
Be sure to read: What Borehole Pump Do You Need? A Complete South African Guide (2026)
This is usually caused by hydrogen sulphide from bacterial activity in groundwater.
Often due to iron in the water oxidising when exposed to air.
It can indicate sand, silt, or contamination and should be tested.
Immediately if smell, colour, or taste changes.
Yes. Groundwater conditions and system issues can alter water quality.