How Much Water to Store Per Person

Planning how much water to store sounds simple until you sit down to do the arithmetic — then the numbers start to feel either absurdly small or impossibly large. This guide breaks the calculation into honest, usable pieces so you can arrive at a figure that actually works for your household in Johannesburg.

Why the standard advice of “2 litres a day” is not enough

You will often see emergency guidance that says store 2 litres per person per day. That figure covers bare survival drinking — nothing else. It ignores hand-washing, oral hygiene, basic food preparation, flushing, and the fact that children, elderly people, and anyone who is ill will need more fluid intake, not less.

For context, South Africans use on average about 237 litres of water per person per day (IWA Water Policy), which is well above the world average of roughly 173 litres. You are clearly not going to store 237 litres per person per day — nor do you need to — but the gap between that daily norm and the “2 litre survival” figure is where realistic planning lives.

A more useful planning minimum is 15–20 litres per person per day. That covers:

• Drinking and cooking: 3–5 litres
• Basic hand-washing and oral hygiene: 3–5 litres
• Basic sanitation (bucket flushing): 5–8 litres
• Food preparation and rinsing: 2–4 litres

If your backup system or tank can deliver more than 20 litres per person per day, you are in a comfortable position. Below 10 litres per person per day, things become genuinely difficult for any outage longer than 24 hours.

Scaling for your household size and outage length

Once you have a daily per-person figure, the rest is multiplication. The table below uses 20 litres per person per day as the planning number — adjust it up or down based on your household’s specific needs.

Household size	3-day supply	7-day supply	14-day supply
1 person	60 L	140 L	280 L
2 people	120 L	280 L	560 L
4 people	240 L	560 L	1 120 L
6 people	360 L	840 L	1 680 L

These numbers assume no replenishment during the outage. In practice, a 3-day outage is the most common scenario in Johannesburg, but extended disruptions — particularly given that Johannesburg’s reservoir system holds roughly 27 hours of citywide storage buffer — can escalate quickly when supply is interrupted for longer than expected. For a detailed look at how to size your storage for a 3-day outage specifically, the WaterQuotes guide on sizing backup water for a 3-day outage walks through the tank and pump considerations.

Adjusting for real-life variables

The table above is a starting point. Several factors will push your actual requirement higher:

Children under five tend to need proportionally more drinking water relative to body weight, and they create more hygiene demand (nappy changes, frequent hand-washing).

Pets are often forgotten. A medium-to-large dog may need 1–2 litres of drinking water per day. Add this to your total.

Medical conditions — dialysis patients, people with kidney conditions, those on certain medications — may have significantly higher hydration requirements. If anyone in your household fits this description, speak to their doctor about the right daily minimum.

Hot weather increases fluid loss. Johannesburg summers are warm and dry. If you are planning summer resilience, add at least 20% to your drinking and cooking figure.

Cooking method matters. If your backup plan involves gas or a fire rather than an electric stove, water loss through boiling and steam may be lower, but food preparation may still demand more water for soaking dried goods.

If you are ready to install a storage tank or backup system sized to your household, get 3 free quotes from vetted installers — no obligation.

Drinking water quality during storage

Storing water is only useful if it remains safe to drink. SANS 241 (2024 edition) is the South African drinking-water quality standard — water supplied by Johannesburg Water should meet this standard, but water stored in tanks can degrade if containers are not clean, sealed, and kept out of direct sunlight.

A few practical points:

• Food-grade containers only. Do not use containers that previously held chemicals, even after washing.
• Opaque or UV-resistant containers slow algae and bacterial growth far more effectively than clear plastic.
• Rotate your supply. Stored municipal water in a sealed, clean container is generally safe for several months, but it is sensible to rotate stock every few months if you are maintaining a standing emergency supply rather than drawing from a live tank.
• Consider treatment for longer-term storage: a small amount of unscented household bleach (sodium hypochlorite) can extend safe storage life — follow verified guidelines on concentration, as too much is harmful and too little is ineffective.

For more on container choice and treatment options, the WaterQuotes guide on how to store water for an outage goes into practical detail.

Choosing between stored tanks and a live backup system

Once you know your daily litres-per-person requirement and your target number of days, you have two broad options: passive stored reserves (JoJo-style tanks filled from the mains when supply is available) or an active backup system that draws on a borehole or harvested rainwater.

Passive tank storage is the lower-cost entry point. Backup tank-and-pump systems typically run R20,000–R40,000, with whole-house examples around R55,000. These work well for short outages if you can pre-fill before a disruption and if Johannesburg Water’s non-revenue water losses — currently 44.8% according to 2024/25 audited figures, reflecting significant infrastructure pressure — do not leave you with insufficient pressure to refill.

For longer resilience or households with higher demand, a borehole system provides a live supply that is independent of the municipal network. Typical complete borehole systems in Johannesburg run R40,000–R150,000, with most falling between R60,000 and R100,000. The WaterQuotes resilience hub at /blog/ has comparison articles covering both options in more detail.

Not sure which storage or supply option fits your budget and household size? Compare quotes from local specialists — vetted installers, no obligation.

Putting it all together: a simple planning checklist

Before you buy a tank or fill a container, run through this:

1. Count everyone in the household, including regular visitors and any live-in domestic workers.
2. Set your daily minimum — 15 litres per person if you want a strict floor, 20 litres for a more comfortable baseline.
3. Decide your target duration — 3 days is the common starting point, but 7 days gives meaningful resilience against extended outages.
4. Add variables — pets, medical needs, hot season adjustment.
5. Divide by your container or tank capacity to see how many units you need.
6. Plan for quality — sealed containers, rotation schedule, and treatment if storing for longer periods.

The arithmetic is not complicated; what catches people out is underestimating the daily per-person figure or forgetting the variables. Start with an honest number and size upward from there.