Boiling Water Safely During a Contamination Notice

When Johannesburg Water issues a boil-water notice, the guidance can feel vague — ‘boil before use’ without much detail on what that actually means in practice. This article walks through what the process involves, where it falls short, and how to store water safely once it has been treated. For a broader look at water resilience in Johannesburg, the WaterQuotes resource hub covers everything from backup systems to understanding municipal supply.

What a boil-water notice actually means

A boil-water notice is a formal advisory, typically issued when microbial contamination — bacteria, protozoa, or viruses — is detected or suspected in the municipal supply. In South Africa, drinking water quality is governed by SANS 241 (2024 edition), administered by the South African Bureau of Standards. When supply falls outside those parameters, authorities are expected to notify affected households.

The notice does not always mean every tap in Johannesburg is affected. Notices are often zone-specific, tied to a burst main, reservoir ingress, or treatment plant fault. Check the Johannesburg Water website or their official social media channels for the geographic scope before assuming your supply is compromised — or before assuming it is safe.

The correct boiling procedure

Boiling is effective against biological pathogens when done properly. Here is what the process involves:

1. Let the water settle first. If your tap water is visibly turbid (cloudy or silty), let it sit for a few minutes and pour it through a clean cloth or coffee filter before boiling. Suspended particles can shield microorganisms from heat.
2. Bring to a full rolling boil. A rolling boil — where the water churns vigorously, not just simmers — is the target. One minute at a rolling boil is the standard guidance at Johannesburg’s altitude (roughly 1,700 m above sea level). At higher altitudes, water boils at a lower temperature, so some guidelines recommend two minutes; one minute is a conservative minimum for Johannesburg.
3. Do not re-contaminate the water. Use a clean pot. Do not pour boiled water back into an unwashed container or stir it with an unwashed spoon.
4. Cool before storing. Allow the water to cool naturally — do not speed this up by adding ice (which may itself be contaminated).

Boiling does not remove chemical contaminants, heavy metals, or dissolved salts. If the notice specifies chemical contamination, boiling is insufficient and you should follow the specific instructions issued by the relevant authority.

Safe storage after boiling

How you store boiled water matters as much as how you boil it. Recontamination at the storage stage is a real risk.

• Use food-grade containers with tight-fitting lids. Glass, stainless steel, or BPA-free plastic are all acceptable.
• Label the container with the date and time of boiling.
• Store in a cool, dark place away from direct sunlight.
• As a rough guide, boiled water stored in a sealed container at room temperature is generally considered acceptable for up to 24 hours; refrigerated, up to 3 days — but confirm this with current NICD or municipal guidance, as recommendations can vary depending on the nature of the contamination event.
• Wash your hands thoroughly with soap and water (or hand sanitiser if water is scarce) before handling storage containers.

For more on what to do when your only water source is uncertain, our article on drinking water safely in an emergency covers additional treatment options including chemical disinfection tablets.

If boil-water notices in your area are becoming routine, it may be worth looking at a backup supply. Compare 3 free quotes — vetted installers, no obligation.

What boiling does and does not address

Contaminant type	Boiling effective?	Notes
Bacteria (e.g. E. coli, Cholera)	Yes	Standard rolling boil
Protozoa (e.g. Giardia, Cryptosporidium)	Yes	Heat-sensitive at boiling point
Viruses (e.g. Hepatitis A, Norovirus)	Yes	Heat-sensitive
Chemical contaminants	No	Requires filtration or alternative supply
Heavy metals (e.g. lead)	No	Boiling can concentrate some metals
Nitrates	No	Can concentrate with prolonged boiling

If there is any uncertainty about the type of contamination, the safest approach is to seek specific written guidance from Johannesburg Water or the National Institute for Communicable Diseases (NICD) rather than assuming boiling covers all risks.

Using water for purposes other than drinking

During a boil-water notice, the precautions extend beyond drinking water. As a general guide:

• Cooking: Use boiled or bottled water for any food that will not reach a full boil during cooking — salads, cold dishes, ice cubes, baby formula.
• Brushing teeth: Use boiled or bottled water. Rinsing with unboiled tap water during a notice carries the same risk as drinking it.
• Bathing and showering: Typically considered lower risk for healthy adults (avoid swallowing water). Extra caution is warranted for infants, the immunocompromised, and anyone with open wounds. If in doubt, follow the specific advisory issued.
• Washing dishes: A dishwasher with a heated drying cycle may be acceptable; hand-washing should use boiled water for the final rinse, or dishes should be allowed to air-dry completely.

Johannesburg’s municipal system holds roughly 27 hours of citywide storage buffer, which means a contamination event can take time to clear through the network even after the source is resolved. Do not assume the notice has been lifted until you see an official update from Johannesburg Water.

Understanding the broader context

Johannesburg Water’s own figures show non-revenue water — water lost to leaks, theft, and metering errors — running at 44.8% in 2024/25. That level of network stress contributes to pressure fluctuations and potential ingress points where contamination can enter the system. Boil-water notices are, in part, a symptom of an ageing network under considerable strain.

For context on what those notices typically cover and how they are issued, our article on boil-water notices in Joburg explains the municipal process and what to look for.

If your household is frequently affected by notices or supply interruptions, it is worth considering whether a backup water system — a tank and pump, or a borehole — might make practical sense. Backup tank-and-pump systems typically cost R20,000–R40,000 for a standard installation, with whole-house configurations running around R55,000, though you should get specific quotes for your property.

Weighing up whether a backup supply is worth it for your home? Get free quotes from local installers and compare what a real solution would cost you.

When to seek further guidance

Boiling is a practical, low-cost first line of defence against biological contamination. It is not a substitute for knowing what specific contaminant has triggered the notice. If you have health concerns — particularly for infants, elderly household members, or anyone who is immunocompromised — contact your GP or a public health professional rather than relying solely on general guidance. NICD publishes updated advisories during significant contamination events; their guidance should be treated as authoritative alongside any official Johannesburg Water communication.

Test your water independently if the situation is prolonged or unclear. Several accredited laboratories in Gauteng offer residential water testing at a reasonable cost — ring around for quotes, and ensure any lab you use is SANAS-accredited for water analysis.