Water quality · lab results
Borehole water test results: drink it, water the garden, or treat it?
A lab report on borehole water answers three different questions: can you drink it, can it go on the garden, and will it clog a drip line. The answer also decides how much the borehole saves, because water you can drink replaces the dearest part of the bill in some metros and nothing in others.
By Borehole Payback · updated 24 October 2026
What our numbers show
SANS 241 drinking-water limits; DWAF South African Water Quality Guidelines vol. 4 (irrigation); our payback model for five metros
- The limits for the three uses are far apart. Iron above 0.3 mg/L fails SANS 241 for drinking because it stains and tastes, yet the national irrigation guideline accepts up to 5 mg/L on the soil, and drip lines already start to clog above 0.2 mg/L.
- What the water may be used for moves the payback more than the test itself. A 60 m borehole watering a 250 m² lawn in eThekwini pays back in 19.8 yrs in our model; if it also supplies the whole house, 6.5 yrs.
- Treating water to drinking standard pays where the first kilolitres are dear. Taking the last 9 kl of a 15 kl household off the municipal supply is worth R5 582 a year in eThekwini, R3 576 in Ekurhuleni and R1 158 in Johannesburg after pump electricity. In Tshwane, where the first 9 kl are free, it saves nothing.
- To pay for itself over ten years, a treatment system for the whole house, with its cartridges and lamps, must cost less than about R55 822 in eThekwini and R11 580 in Johannesburg.
Read your lab report
Filled in with an example: water with iron, otherwise within the limits. Replace the numbers with your report; leave a box empty if it was not tested. Iron and manganese in mg/L (1 000 µg/L = 1 mg/L).
Drinking
Garden, sprinkler
Drip irrigation
Payback of a 60 m borehole with a 250 m² lawn
| What the borehole supplies | Treatment | Pays back in |
|---|
The limits side by side
| Test | Drinking (SANS 241) | Garden (irrigation guideline) | Drip lines |
|---|---|---|---|
| E. coli, per 100 mL | not detected | ≤ 1 for crops eaten raw; ≤ 1 000 for crops not eaten raw | – |
| Nitrate as N, mg/L | ≤ 11 | – | – |
| Fluoride, mg/L | ≤ 1.5 | ≤ 2 | – |
| Arsenic, µg/L | ≤ 10 | ≤ 100 | – |
| Iron, mg/L | ≤ 0.3 (taste, stains) | ≤ 5 | < 0.2 little clogging, > 1.5 severe |
| Manganese, mg/L | ≤ 0.1 (stains) | ≤ 0.02 on all soils; up to 10 on fine-textured neutral to alkaline soils | < 0.1 little clogging, > 1.5 severe |
| Conductivity (EC), mS/m | ≤ 170 | ≤ 40 for all plants | – |
| pH | 5–9.7 | 6.5–8.4 | above 8.4: scale |
| Sodium, mg/L | ≤ 200 | ≤ 70 where leaves get wet | – |
| Chloride, mg/L | ≤ 250 (300 in the 2015 edition) | ≤ 100 on wet leaves, < 140 on the soil | – |
Garden column: the target range of the national irrigation guideline for unrestricted use on all soils. Drinking: health limits for E. coli, nitrate, fluoride and arsenic; the rest are taste and staining limits.
Does drinkable water pay? Five metros
| Metro | Garden only | Plus toilets and laundry | Whole house | Extra a year for drinking quality |
|---|---|---|---|---|
| eThekwini (Durban) | 19.8 yrs | 10.6 yrs | 6.5 yrs | R5 582 |
| Ekurhuleni (East Rand) | 8.3 yrs | 6.4 yrs | 5.2 yrs | R3 576 |
| Cape Town | 7.4 yrs | 5.8 yrs | 5 yrs | R2 811 |
| Johannesburg | 8.9 yrs | 7.1 yrs | 6.5 yrs | R1 158 |
| Tshwane (Pretoria) | 8.5 yrs | 6.8 yrs | 6.9 yrs | R0 |
Our model: 60 m borehole costing R94 500, 250 m² lawn, 15 kl a month used in the house. "Plus toilets and laundry" moves 6 kl a month to the borehole, "whole house" all 15 kl; sewage stays billed on indoor use. No treatment cost included: the last column is what drinking-quality water is worth a year over toilets and laundry alone.
The order follows the price of the first kilolitres. eThekwini charges from the first litre and its lowest block is the dearest of the five, so drinking-quality water is worth most there. Johannesburg gives the first 6 kl free and Tshwane the first 9 kl, so the borehole would replace water that costs little or nothing, while the pump still uses electricity.
What treatment fixes what
- Bacteria (E. coli, coliforms): a sediment filter and a UV lamp, or chlorination, on the line into the house.
- Iron and manganese: oxidation and filtration (an iron filter) before the house, or let a tank stand so the iron settles. For a lawn on sprinklers no treatment is needed; drip systems need it, or a switch to sprinklers.
- Nitrate, fluoride, arsenic or salt: only reverse osmosis removes them, usually at one kitchen tap. For a household that means keeping municipal water for drinking and cooking.
Whatever the result, keep the borehole pipes completely separate from the municipal supply; in Cape Town groundwater may not generally be used for drinking at all. See borehole rules and the payback calculator.
Questions owners ask
Can I tell from the look of the water whether it is safe?
No. E. coli, nitrate, fluoride and arsenic do not change colour, taste or smell. Clear water can fail the health limits, and orange water from iron can be harmless to drink. Only a lab test shows it.
How often should borehole water be tested?
Before you first use it, and again if the colour, taste or smell changes or after a flood. For small community borehole supplies, the draft of the new SANS 241 asks for arsenic, fluoride, iron, manganese, nitrate, nitrite and heterotrophic bacteria at least twice a year; that is a good list for a household test too.
Why does my borehole water stain orange or black?
Orange-brown stains come from iron above about 0.3 mg/L, black ones from manganese above 0.1 mg/L. These are the SANS 241 aesthetic limits; the 2015 edition also set health limits at 2 mg/L iron and 0.4 mg/L manganese. On a lawn neither is a problem at those levels, but both clog drip emitters.