Borehole Water Quality Testing

Water that looks clear is not necessarily safe. Groundwater can carry dissolved minerals from the rocks it flows through, bacteria from nearby latrines or septic tanks, nitrates from fertiliser and sewage, and in some places natural contaminants such as fluoride or arsenic. Many of these cannot be seen, smelled or tasted until concentrations are high, and some, such as fluoride, cause harm only after long exposure.

Testing is therefore the only reliable way to know whether your borehole water is safe for drinking, cooking, livestock, irrigation or industrial use, and what treatment, if any, is required. In Kenya, testing is also part of good practice after drilling and is often part of the documentation for permits and commercial operations.

Which Standards Apply?

Two reference points are commonly used:

• World Health Organization (WHO) Guidelines for Drinking-water Quality, the international benchmark for health-based limits.
• Kenyan standards, notably the Kenya Standard KS EAS 12 (drinking water specification) administered by the Kenya Bureau of Standards (KEBS), and regulations used by the Water Services Regulatory Board (WASREB) and the National Environment Management Authority (NEMA) for effluent and environmental quality.

Values in this article are based on WHO guidelines and typical practice. Standards are updated from time to time, so ask your accredited laboratory which version it uses and compare results with the current Kenyan standard.

The Core Parameters to Test

A sensible borehole water test covers physical, chemical and microbiological parameters.

1. Fluoride. Fluoride occurs naturally in volcanic and some basement rocks and is a major concern in the Kenyan Rift Valley and parts of the highlands. The WHO guideline value is 1.5 mg/L. At low levels (around 0.5 to 1.0 mg/L) fluoride helps prevent tooth decay, but long-term intake above 1.5 mg/L can cause dental fluorosis (mottled, stained teeth), and at higher levels, skeletal fluorosis, which affects bones and joints. Studies in Nakuru County have recorded fluoride from 0.5 up to 72 mg/L, with a mean above 11 mg/L, and county sampling in Naivasha and nearby areas has found boreholes between about 2 and 6.5 mg/L. Always test for fluoride in the Rift Valley and in volcanic areas. See our dedicated fluoride article.

2. Total dissolved solids (TDS) and electrical conductivity (EC). TDS measures all dissolved minerals and salts. EC is a quick proxy because dissolved ions conduct electricity. WHO does not set a health-based limit for TDS, but water above roughly 600 mg/L begins to taste noticeably salty, and above about 1,000 mg/L it is increasingly unpalatable. Many standards allow up to around 1,000 to 1,500 mg/L for drinking water, though lower is better. High TDS also affects irrigation suitability and livestock health. Salinity is a frequent concern in arid and coastal areas and parts of the Rift floor.

3. Hardness (calcium and magnesium). Hardness is mostly calcium and magnesium, expressed as mg/L as CaCO₃. There is no health-based WHO limit, but hard water leaves scale in kettles, pipes, heaters and irrigation systems and reduces soap lathering. A rough scale: below 60 mg/L soft, 60 to 120 moderately hard, 120 to 180 hard and above 180 very hard. Volcanic and limestone aquifers can produce hard water. Hardness is mainly a nuisance and cost issue, but it can shorten equipment life.

4. pH. pH measures acidity or alkalinity. A typical acceptable range for drinking water is about 6.5 to 8.5. Very acidic water corrodes pipes and pumps, and very alkaline water can cause scaling and taste problems. Many Rift Valley groundwaters are alkaline and sodium-bicarbonate dominated.

5. Nitrate and nitrite. Nitrate comes from fertilisers, animal waste and sewage. The WHO guideline is 50 mg/L as nitrate (and a much lower value for nitrite) because high nitrate can cause methaemoglobinaemia (blue baby syndrome) in infants. Shallow boreholes near farms, latrines and septic systems are most at risk.

6. Microbiological quality (total coliforms and E. coli). Faecal contamination can cause cholera, typhoid, dysentery and diarrhoeal diseases. The standard for drinking water is no detectable E. coli per 100 mL. Test after construction and regularly thereafter, especially after floods or repairs, and where latrines or septic tanks are close. Newly drilled boreholes should be disinfected before first use.

7. Iron and manganese. These cause reddish-brown or black staining, metallic taste and clogging of pipes and screens. WHO treats them mainly as aesthetic and operational issues. Iron is common in western Kenya and in some basement and sedimentary aquifers. High iron can also promote iron bacteria that clog boreholes.

8. Chloride, sulphate and sodium. These contribute to salty taste, corrosion and scale. High chloride can indicate saline influence or pollution. High sodium is relevant to irrigation, since it can damage soil structure, and for people on sodium-restricted diets.

9. Alkalinity and bicarbonate. Relevant to scaling and corrosion tendencies and to interpreting water chemistry.

10. Turbidity, colour, taste and odour. Simple physical indicators. High turbidity may indicate sand or clay entering the borehole or contamination.

Additional Parameters to Consider

Depending on location and land use, add:

• Arsenic (health-based guideline 10 µg/L), relevant in some geothermal and volcanic settings.
• Heavy metals such as lead, cadmium, chromium and mercury, where mining, industry or old infrastructure may contribute.
• Pesticides and hydrocarbons near intensive agriculture, fuel stations or industrial areas.
• Boron, which can harm sensitive crops and is sometimes elevated in geothermal-influenced groundwater.
• Radioactivity in certain geological settings, on advice from a specialist.
• Temperature, which can indicate geothermal influence.

Discuss your site’s risks with a hydrogeologist or laboratory to tailor the test list.

Quick Reference Table

Parameter	Reference value (drinking water)	Why it matters
Fluoride	1.5 mg/L (WHO guideline)	Dental and skeletal fluorosis
Nitrate	50 mg/L as NO₃⁻ (WHO)	Infant health risk
E. coli	Not detectable per 100 mL	Disease-causing contamination
pH	About 6.5 to 8.5	Corrosion, scaling, taste
TDS	Ideally below 600 to 1,000 mg/L	Taste, irrigation, livestock
Hardness	No health limit; above 180 mg/L very hard	Scale, soap use, equipment life
Iron	Aesthetic issues above about 0.3 mg/L	Staining, taste, clogging
Arsenic	10 µg/L (WHO provisional)	Long-term health effects

Check your laboratory’s reference standard (WHO or KS EAS 12) for the exact limits it applies.

How to Collect a Proper Water Sample

Results are only as good as the sample. Follow these steps:

1. Ask the laboratory for clean sample containers and instructions. Bacteriological samples need sterile bottles, and chemical samples may need specific containers or preservatives.
2. Sample after pumping for a while. For a new borehole, collect samples near the end of the test pumping, when the water represents aquifer conditions. For existing boreholes, run the pump for several minutes and flush the pipes first.
3. Avoid contamination. Do not touch the inside of the bottle or cap. For bacteriology, sample from a clean tap, disinfected with flame or alcohol if appropriate.
4. Rinse chemical sample bottles with the water to be sampled, unless instructed otherwise, and fill them as directed.
5. Label clearly with date, time, location, borehole details and who collected it.
6. Keep samples cool and deliver quickly. Microbiological samples generally need to reach the lab within hours (commonly within 6 to 24 hours, kept on ice).
7. Record field measurements such as pH, EC and temperature at the borehole, since they can change in transit.

Choosing a Laboratory

Look for a laboratory with accreditation (for example ISO/IEC 17025) or recognition by relevant authorities, and with a track record in water analysis. Universities, public analytical labs, and private accredited laboratories in Nairobi and other cities offer water analysis services. Ask about:

• The list of parameters and detection limits.
• Turnaround time and cost.
• Whether results are compared to WHO or Kenyan standards.
• Whether they provide interpretation or only raw numbers.

Interpreting Your Results

Look at each parameter against the standard, and also at the overall chemistry. A hydrogeologist can interpret patterns, for example:

• High fluoride with high sodium and bicarbonate and high pH is typical of rift groundwater, where volcanic glass and minerals dissolve and evaporation concentrates fluoride.
• High chloride and TDS may indicate salinity from evaporation, old connate water or seawater intrusion.
• High nitrate with bacteria suggests surface or sanitation contamination.
• High iron and low pH may point to reducing, oxygen-poor conditions or acidic groundwater.

If any result exceeds guideline values, do not rely on boiling to fix it. Boiling kills bacteria but does not remove fluoride, nitrate, salts or most chemicals, and can concentrate them.

What To Do If Results Are Poor

Bacteria present: Find and fix the contamination source (improper sealing, nearby latrine, damaged casing), disinfect the borehole and plumbing (typically with chlorine following recommended procedures) and retest. Consider chlorination or UV treatment for ongoing protection.

High fluoride: Options include sourcing water from a different aquifer or depth, blending with low-fluoride water, rainwater harvesting for drinking and cooking, and treatment methods such as activated alumina, bone char, reverse osmosis or electrodialysis. Treatment must be properly designed and maintained. Our fluoride article discusses these.

High TDS or salinity: Reverse osmosis can reduce salinity but produces reject brine that must be managed. Alternatively, find a different source or use the water for suitable purposes only.

Hardness: Water softeners (ion exchange), anti-scale devices or limited use of hard water in sensitive equipment.

Nitrate: Identify the source, consider ion exchange, reverse osmosis or alternative sources, and protect infants by using safe water for formula.

Iron and manganese: Aeration and filtration, oxidation with chlorine or other oxidants, or specialised filters.

Always consult a qualified water treatment professional and verify treated water quality afterward.

How Often Should You Test?

• Before using the borehole, as soon as it has been developed and test pumped.
• At least annually for chemical parameters under stable conditions, and more often where quality is marginal or changing.
• Bacteriological testing every few months, and after floods, repairs, pump replacement or any change in taste or appearance.
• After any nearby change, such as new latrines, fuel storage or intense agriculture.
• For commercial or public supplies, follow the schedule required by regulators and standards.

Keep a record file of all results. Trends over time can reveal gradual deterioration, such as rising salinity from over-pumping or increasing nitrate from land use.

Testing for Irrigation and Livestock

Water that is safe for people may not suit crops or animals, and vice versa. For irrigation, key parameters include electrical conductivity (salinity), sodium adsorption ratio (SAR), boron, chloride and bicarbonate. High sodium relative to calcium and magnesium damages soil structure, while high salinity reduces crop yield. For livestock, high fluoride, sulphate, nitrate and salinity can reduce health and productivity. Commercial horticulture and flower farms should consult a hydrogeologist and agronomist for crop-specific limits.

Frequently Asked Questions

Can I test water at home? Simple test kits and meters can measure pH, EC or TDS and give rough indications of some chemicals. They are useful for screening and monitoring but not a substitute for laboratory analysis, especially for fluoride, bacteria and trace contaminants.

Is clear borehole water always safe? No. Fluoride, nitrate, bacteria and dissolved salts are not visible.

How much does a water test cost? Prices vary widely by laboratory and parameters. Basic panels may cost a few thousand shillings, while comprehensive analyses cost considerably more. Request a quotation.

Does boiling make water safe? It kills bacteria but does not remove fluoride, nitrate, salts or heavy metals.

Should I test before I buy land with a borehole? Yes. A water quality test and a review of the permit status protect you from costly surprises.

Conclusion

Borehole water quality testing is a basic safeguard for health, equipment and investment. At minimum, test for fluoride, TDS or salinity, hardness, pH, nitrate and bacteria, and add parameters as site conditions require. Collect samples carefully, use a reliable laboratory, interpret results in context and act on problems with appropriate treatment or alternative sources.

For help planning water quality testing and understanding what the results mean for your borehole, contact Reg. Geol. Mbugua Githae (MGSK) through consult.innercoregeoconsultants.co.ke.