Last reviewed: October 16, 2026 | By Ugochukwu Dike
Whether your drinking water comes from a borehole, tanker, tap, water-storage tank or sachet, safety starts with understanding where the water comes from and how it is handled. Water can look clear and still contain harmful microorganisms or chemicals.
The World Health Organization (WHO) identifies faecal contamination as a major risk to drinking-water safety. Contaminated water can transmit diseases such as cholera, dysentery, typhoid and polio [1].
Clear water is not always safe
Bacteria, viruses and parasites are generally too small to see with the naked eye. Water may therefore look, smell and taste normal while still containing disease-causing microorganisms [1][2].
Possible sources of contamination around the home include:
Boreholes affected by leaking septic systems, pit latrines, flooding or polluted groundwater.
Storage tanks that are uncovered, poorly maintained or contaminated during filling.
Water containers handled with dirty hands or contaminated cups.
Tanker water from an unsafe source or transported in an inadequately cleaned tank.
Chemical contamination is a separate concern. Boiling can kill many disease-causing microorganisms, but it does not remove harmful chemicals such as lead, fuel or pesticides. If chemical contamination is suspected, use a known-safe alternative source and seek advice from the relevant water or environmental health authority [2][3].
Step 1: Know your water source and test it
Do not judge water safety by appearance alone.
Test borehole water. Ask a qualified water-testing laboratory to test for microbial contamination, including E. coli, and for relevant chemical contaminants based on local risks.
Check after flooding or damage. Flooding, damaged borehole infrastructure or suspected sewage contamination can affect water quality. Use an alternative safe source until the water has been assessed and made safe.
Inspect the surroundings. Look for damaged borehole covers, poor drainage, leaking septic systems and other possible routes through which contaminants could enter groundwater.
Check tanker and stored water. Find out where the water comes from and whether the delivery tank and household storage tank are clean and properly maintained.
Repeat testing when necessary. Test after suspected contamination, repairs or other events that could affect water quality. Ask your local environmental health or water authority about suitable testing intervals.
Testing for E. coli can help identify faecal contamination, but a satisfactory microbial result does not automatically prove that water is free of harmful chemicals [1].
Step 2: Choose the right water-treatment method
The appropriate treatment depends on the contaminant. A method that kills germs may not remove dissolved chemicals, and a filter that improves taste may not remove disease-causing organisms [2][3].
Boiling water
If microbial contamination is suspected and chemical contamination is not, boiling is an effective way to make water safer.
If the water is cloudy, allow particles to settle and filter the clearer water through a clean cloth or suitable pre-filter.
Bring the clearer water to a rolling boil for one minute [2].
Allow it to cool naturally.
Store it in a clean, sanitised container with a tight-fitting cover [2].
Important: Straining water through a cloth removes some particles but does not reliably remove germs. Boiling does not remove harmful chemicals. If the water may contain fuel, pesticides, industrial chemicals or other toxic substances, do not rely on boiling to make it safe [2][3].
Chlorine tablets and other disinfectants
Suitable chlorine-based products can kill many disease-causing microorganisms when used correctly. However, effectiveness depends on the product, water quality, dose and contact time [3][4].
Use a product specifically intended for treating drinking water.
Follow the manufacturer's instructions for the amount of water, dosage and contact time.
Do not guess how much household bleach to add. Not every bleach product is suitable for drinking-water treatment.
If water is cloudy, remove particles first according to the product instructions.
Remember that routine chlorine treatment does not remove harmful chemicals and may not be effective against every parasite [3].
Water filters
Choose a filter according to the contaminant you need to remove. Some filters mainly improve taste or remove particles; others are designed to reduce particular microorganisms or chemicals. A filter that removes bacteria may not remove viruses, lead or pesticides [3][4].
Check the manufacturer's performance claims, certification or independent testing, maintenance requirements and replacement schedule. Some filtered water may need additional disinfection.
When household treatment is not enough
If you suspect that water contains fuel, industrial chemicals, pesticides or other toxic substances, use a known-safe alternative source. Boiling and routine disinfection will not make chemically contaminated water safe [2][3].
Step 3: Store drinking water safely
Water can become contaminated again after treatment if it is handled or stored poorly [5].
Use clean containers with tight-fitting covers.
Prefer containers with a narrow opening or a tap so that hands and cups do not enter the water.
Wash your hands before handling drinking-water containers.
Clean storage containers regularly using a suitable method and safe water.
Keep tanks and buckets covered and protect them from dirt, insects and other sources of contamination.
Inspect tanks for cracks, damaged covers, sediment or signs of contamination. If a tank is flooded or contaminated, arrange appropriate cleaning and disinfection before using it again.
Step 4: Protect the whole water system
Safe water depends on more than treatment at the point of drinking.
Keep toilets, septic systems and soakaways appropriately separated from wells and boreholes according to local regulations and site conditions.
Repair leaking pipes and protect borehole openings from surface runoff.
Keep drainage around water sources in good condition.
Wash your hands with soap after using the toilet and before preparing food.
For packaged water, check that the seal is intact and the packaging appears undamaged. In Nigeria, check the NAFDAC registration details and report suspected counterfeit or unsafe products to the appropriate authority.
What about water for babies?
Infant feeding requires extra care. Powdered infant formula is not sterile, and preparation recommendations can differ according to the baby's age, health and circumstances. Follow the product instructions and current guidance from a qualified health worker. Use water from a safe source, and do not assume that boiling alone makes water containing harmful chemicals safe.
When to get medical help
Seek medical care if someone develops persistent diarrhoea, repeated vomiting, fever, blood in the stool or signs of dehydration. Warning signs of dehydration include very little urine, unusual sleepiness, sunken eyes and extreme thirst.
Babies and young children can become dehydrated quickly. If severe watery diarrhoea occurs, seek urgent medical care and give oral rehydration solution (ORS) while arranging care, following the packet instructions. Severe dehydration requires prompt treatment [6].
Conclusion
Making drinking water safer at home involves four habits: knowing your source, choosing the right treatment, storing water hygienically and maintaining good sanitation. Boiling can help control microbial contamination, but it is not a universal solution for every water-quality problem. Suspected chemical contamination requires a different response and may require professional testing.
If you are concerned about your borehole, tanker supply or household storage tank, contact your local environmental health officer or water authority for advice.
This article provides general health information and is not a substitute for professional water testing or medical advice.
About the author: Ugochukwu Dike holds a B.Sc. (Hons) in Anatomy from the University of Calabar and is studying for a B.Sc. in Environmental Health Science at the National Open University of Nigeria.
References
World Health Organization (WHO). Drinking-water. https://www.who.int/en/news-room/fact-sheets/detail/drinking-water
Centers for Disease Control and Prevention (CDC). How to Make Water Safe in an Emergency. https://www.cdc.gov/water-emergency/about/
Centers for Disease Control and Prevention (CDC). Household Water Treatment. https://www.cdc.gov/global-water-sanitation-hygiene/about/about-household-water-treatment.html
World Health Organization (WHO). Household Water Treatment and Safe Storage. https://www.who.int/teams/environment-climate-change-and-health/water-sanitation-and-health/water-safety-and-quality/household-water-treatment-and-safe-storage
World Health Organization (WHO). Household Water Treatment and Safe Storage Following Emergencies and Disasters. https://www.who.int/publications/m/item/household-water-treatment-and-safe-storage-following-emergencies-and-disasters
World Health Organization (WHO). Cholera. https://www.who.int/news-room/fact-sheets/detail/cholera
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