How to Store Water for an Outage Safely

Johannesburg’s water network loses nearly half its supply before it reaches a tap — Johannesburg Water’s own audited figures put non-revenue water at 44.8% for 2024/25. Add the fact that the city’s reservoir system holds roughly 27 hours of citywide storage buffer, and the arithmetic is uncomfortable: a single serious pipe failure or infrastructure event can empty local reservoirs faster than most households expect. Storing water at home is one of the few things entirely within your control. Done correctly, it costs little and keeps your household functional through short outages. Done carelessly, stored water becomes a contamination risk in its own right.

This guide covers what you actually need to know — containers, quantities, treatment, and rotation — without overstating the risks or underselling the effort involved.

Why stored water goes bad

Water itself does not expire, but the container it lives in, and the microorganisms that may enter it, absolutely do change over time. Municipal tap water in Johannesburg is treated with a residual disinfectant — typically chlorine — that dissipates within days to weeks depending on temperature, light exposure, and how well the container is sealed. Once that residual is gone, any bacteria introduced during filling can multiply. Algae can grow in clear containers exposed to light. Plasticiser compounds can leach from containers not rated for long-term water storage.

The National Institute for Communicable Diseases (NICD) consistently flags waterborne pathogens — including Cryptosporidium, E. coli, and Vibrio species — as significant risks when water handling hygiene lapses. This is not theoretical: contaminated stored water that looks and smells fine can still carry a meaningful microbial load. Test first, treat second is the right instinct.

Choosing the right containers

Not every container you own is suitable. The key criteria are:

• Food-grade plastic or stainless steel. Look for containers marked HDPE (high-density polyethylene), usually with a recycling symbol and the number 2, or those labelled food-safe. Avoid containers that previously held chemicals, bleach, or anything toxic — residues cling even after washing.
• Opaque or UV-blocking material. Clear containers allow light in and accelerate algae growth and chemical breakdown.
• A tight-sealing lid. Loose or cracked lids admit insects, dust, and airborne contamination.
• Manageable size. A 25-litre jerry can is a practical upper limit for most people to move safely. Larger static tanks (100–1 000 litres or more) work well if they are installed correctly and never need to be carried.

Commercially available water-storage jerry cans, purpose-built stackable tanks, and food-grade intermediate bulk containers (IBCs) are all reasonable options depending on your available space. The South African Bureau of Standards (SABS) sets standards for plastic containers intended for food and water contact — when buying locally, checking for SABS mark conformance on the product or from the supplier is a reasonable due-diligence step.

Avoid repurposed milk jugs and thin single-use water bottles for medium or long-term storage. The plastic degrades, seals are poor, and they are difficult to clean adequately.

How much water to store

South Africans use roughly 237 litres per person per day on average — well above the global average of around 173 litres — but that figure includes garden irrigation, long showers, and other non-survival uses. For emergency storage, the calculation is different.

Purpose	Litres per person per day (minimum)
Drinking	2–3
Basic cooking and food hygiene	3–5
Basic personal hygiene (no shower)	5–10
Practical minimum total	10–15

For a 3-day supply, a household of four needs roughly 120–180 litres at the practical minimum — and that assumes disciplined rationing. A 5-day supply pushes that to 200–300 litres. These are rough guides; your actual household needs may differ, and a quick quote from an installer can help you size a permanent storage solution appropriately.

For context, purpose-built backup tank-and-pump systems typically cost R20,000–R40,000 for smaller residential setups, with whole-house examples running around R55,000. If a larger, integrated solution makes sense for your situation, the WaterQuotes blog covers the broader landscape of backup water options in Johannesburg.

Thinking about a permanent tank rather than jerry cans? Compare 3 free quotes — vetted installers, no obligation.

Filling, treating, and labelling

Fill containers from a running municipal tap — not from a hose that has been sitting in the sun, and not from an outdoor tap that may not have been used recently. Let the tap run for 10–15 seconds before filling if it has been idle.

For short-term storage (two to four weeks), properly sealed containers filled from a treated municipal supply generally do not need additional treatment. For longer storage, or if you have any doubt about the source, the common household approach is to add food-grade sodium hypochlorite (ordinary unscented household bleach, typically 3.5–5% active chlorine). A rough guide is 2 drops per litre, though this varies with bleach concentration — check the product label and confirm dosage before use. Do not use scented bleach or bleach with added surfactants.

Label every container clearly with:

• The fill date
• The water source (municipal, borehole, rainwater)
• Any treatment added

This is not bureaucracy — it is how you avoid drinking 18-month-old untreated borehole water because the label fell off.

Note that SANS 241 (2024 edition) is the South African drinking-water quality standard. Your stored water is not tested to that standard unless you have actually had it tested. If you are storing borehole or rainwater rather than municipal supply, independent laboratory testing before you drink it — especially for microbiological parameters — is strongly advisable.

Rotation and maintenance

Even with proper treatment, stored water should be rotated. A practical rotation schedule:

• Municipal water in sealed food-grade containers: replace every 6–12 months as a conservative guide
• Treated water with added bleach: replace every 6 months
• Borehole or rainwater: test before use; do not assume prior test results still apply

When you rotate, use the old water first (for garden irrigation, cleaning, or flushing) before refilling with fresh supply. Rinse containers with a dilute bleach solution, allow them to air-dry, and then refill. Do not skip the rinse — biofilm can establish itself on container walls and persist through simple water replacement.

Store containers away from direct sunlight, away from heat sources, and — critically — away from fuel, paint, pesticides, or cleaning chemicals. Plastic is permeable to volatile organic compounds over time.

A permanent backup tank removes the rotation burden entirely — and may cost less than you expect. Get free quotes from local installers and see what options suit your property.

When stored water is not enough

Jerry cans and a disciplined rotation schedule are a reasonable first line of resilience for a few days. They are not a substitute for a properly designed backup water system if your household faces frequent or prolonged outages. Borehole systems in Johannesburg typically run R40,000–R150,000 fully installed, with most falling between R60,000 and R100,000 depending on depth and equipment — a significant outlay, but one that addresses supply rather than just storage. Backup tank systems are a middle option, capturing and storing municipal water when it flows and releasing it when it does not.

Whichever direction you go, the WaterQuotes blog is worth a read before you commit to equipment or installers. Understanding what you are buying — and what questions to ask — is the difference between a system that works and one that sits idle when you need it most.