Reading a Water Test Report

You have received a water test report and it looks like a chemistry exam you did not study for. Rows of abbreviations, numbers with decimal places, and units like mg/L and CFU/100mL — none of it obviously useful. This guide walks through the structure of a typical South African water test report, explains what the main parameters mean, and shows you how to connect each result to a potential treatment step. The guiding principle throughout: test first, treat second.

Why the report structure matters

Most accredited South African laboratories format reports in three broad sections: physical parameters (things you can detect with your senses, such as turbidity and colour), chemical parameters (dissolved substances), and microbiological parameters (bacteria and other organisms). Understanding which section you are reading tells you immediately what kind of risk or nuisance you are dealing with and, crucially, which section of SANS 241 (2024 edition) applies.

SANS 241 is published by the South African Bureau of Standards and sets two classes of limits for many parameters: an aesthetic limit (where water becomes unpleasant but is not necessarily a health risk) and a health limit (where exposure may present a risk). Your report will usually show the measured value, the relevant SANS 241 limit, and a pass/fail or compliant/non-compliant flag. Always look at which limit type is flagged — an aesthetic exceedance calls for a different response than a health exceedance.

Physical parameters: what they indicate

Turbidity is measured in NTU (Nephelometric Turbidity Units) and reflects how cloudy the water is. High turbidity can indicate suspended sediment, organic matter, or — importantly — that disinfection may be less effective, because particles can shield microorganisms. Colour is reported in mg/L Pt/Co units and can signal dissolved organic compounds, iron, or manganese.

Temperature affects how other parameters behave but is usually informational rather than a pass/fail value. pH sits between the physical and chemical sections in many reports; it affects corrosion of pipes and the effectiveness of chlorine disinfection. SANS 241 sets acceptable pH ranges — a result outside those ranges is worth acting on, particularly if you have older metal plumbing.

Chemical parameters: the ones that need the most attention

This is typically the longest section of any report. Here are the parameters Johannesburg homeowners most commonly encounter:

Parameter	Common source	Key concern
Total Dissolved Solids (TDS)	Naturally occurring minerals, pipe corrosion	High TDS affects taste; very high levels may indicate other issues
Nitrates	Agriculture, septic systems, borehole contamination	Health limit applies especially for infants
Iron & Manganese	Geological, ageing infrastructure	Staining, taste; manganese has a health limit in SANS 241
Fluoride	Geological in parts of Gauteng	Health limit applies at higher concentrations
Chlorine (residual)	Municipal treatment	Low residual may indicate distribution risk; very high levels are an aesthetic concern
Hardness (as CaCO₃)	Dissolved calcium and magnesium	Scale on appliances; no health limit but affects equipment life

For each chemical parameter, the key action is straightforward: find the SANS 241 (2024 edition) limit for that parameter, compare it to your measured value, and note whether any exceedance is aesthetic or health-related. Do not assume that a long list of parameters means a long list of problems — many results will be well within limits.

Microbiological parameters: the non-negotiables

Microbiological results are reported as CFU/100mL (colony-forming units per 100 millilitres) or as presence/absence. SANS 241 specifies that E. coli must be absent in a 100mL sample of drinking water — there is no acceptable level. Total coliforms are also measured; their presence in a treated supply does not necessarily confirm faecal contamination, but it indicates a compliance issue that requires investigation.

If your report shows E. coli detected or total coliforms present, treat this as an immediate priority. Do not use the water for drinking or food preparation until the source of contamination is identified and the water is confirmed safe by retesting. The National Institute for Communicable Diseases (NICD) maintains guidance on waterborne disease risks, and their resources are worth consulting alongside your laboratory report. For borehole water especially, microbiological testing should be repeated seasonally, not treated as a once-off exercise.

If you are drawing from a borehole or rainwater tank in Johannesburg, you will benefit from understanding the full range of parameters worth testing — our guide to water testing in Johannesburg covers which tests to request and how to find an accredited laboratory.

Once you know which parameters are out of range, choosing the right treatment system is the logical next step. Compare 3 free quotes — vetted installers, no obligation.

Connecting results to treatment options

This is where many homeowners make an expensive mistake: buying a treatment system before properly reading the report, or buying a system that addresses a parameter that is actually within limits. Treatment should be targeted.

• High turbidity or sediment: sediment pre-filters are typically the starting point before any other treatment.
• Iron or manganese exceedances: dedicated iron-removal filtration or oxidation-filtration systems. Standard carbon filters will not reliably remove dissolved iron.
• Microbiological contamination: UV disinfection, reverse osmosis, or chemical disinfection — depending on the contamination type and how the system will be maintained.
• High nitrates: reverse osmosis or ion exchange. Boiling does not remove nitrates and actually concentrates them.
• Hardness: water softeners (ion exchange) or scale-inhibiting filters, depending on severity and application.
• Taste and odour from chlorine: activated carbon filtration is effective for this specific issue.

Our water filtration pillar covers these treatment categories in depth, including what each system does and does not address — useful context before you speak to any installer.

Getting the report interpreted professionally

If any parameter shows a health exceedance, or if you are uncertain how to read the report, commission a professional interpretation before purchasing equipment. A reputable water-treatment company should be willing to review your actual laboratory report — not just sell you a package — and explain which results are driving their recommendation. Be cautious of any company that recommends a comprehensive multi-stage system without first asking to see your test results.

If you would like installers to review your report and recommend targeted treatment, the most efficient route is to get multiple assessments side by side. Request quotes from vetted water-treatment specialists — free and without commitment.

A practical checklist for reading your report

1. Identify the testing laboratory and confirm it is SANAS-accredited — results from non-accredited laboratories carry less weight.
2. Note the sample date and collection point. A result from six months ago, or from the municipal main rather than your tap, may not reflect current conditions at the point of use.
3. Separate the three sections: physical, chemical, microbiological.
4. For each flagged result, note whether it exceeds the aesthetic limit or the health limit under SANS 241 (2024 edition).
5. List only the parameters that are out of range — this is your treatment priority list.
6. Match each out-of-range parameter to the appropriate treatment method before requesting quotes.
7. Retest after any treatment system is installed to confirm the exceedance has been addressed.

A water test report is only useful if it drives the right action. Reading it carefully, in the structure laid out above, is the step that separates an informed decision from an expensive guess.