How much
Be Ready and the water companies use 3 litres per person per day for drinking; the WHO figure of 2.5 to 3 litres is the same. That's before cooking, teeth, washing hands, formula and the dog. Other governments use anything from 2 to 5 litres a day; see what different governments advise. A workable household rule, per day, to multiply by the number of days you're planning for:
| Who | Drinking, per day | Plus cooking & hygiene | Keep, per day |
|---|---|---|---|
| Each adult or child over 5 | 3 L | +1 L | 4 L |
| Each child under 5 | 2 L | +1.5 L formula, washing | 3.5 L |
| Each dog | 1 L | — | 1 L |
| Each cat | ⅓ L | — | ⅓ L |
| Two adults, two children over 5, a dog | ≈ 17 L a day | ||
Seventeen litres a day is between three and four 5-litre supermarket bottles a day. They stack flat under a bed or on a cupboard floor. Rotate once a year: drink them in the summer, buy ten more.
Three layers, cheapest first
1. Bottled: buy it with the shop
Own-brand still water in 5 L bottles. Keep it cool, dark, off a concrete floor and away from bleach, paint and petrol, because the plastic breathes. Write the month on each bottle.
2. Stored: fill it when the warning comes
A 25 L food-grade container with a tap, filled from the kitchen tap the moment a storm is named or a water company text arrives. Empty it afterwards. If you want to keep it filled permanently, add a purification tablet on filling and change it every six months. Two of them cover a household's washing and flushing water for a day or two. For a parent who can't lift 25 L, a 10 L collapsible carrier.
25 L food-grade jerry can with tap ador6 × 25 L stackable jerry cans ad Starnearby 12 L water container with tap in my kit ador25 L food-grade jerry can with tap ador6 × 25 L stackable jerry cans ad
3. Treated: make other water safe
When bottled water runs out you'll be filling from a bowser, a neighbour's tank, the bath or a water butt. Two tools, and they do different jobs:
- Purification tablets (chlorine-based) kill bacteria and viruses but not Cryptosporidium. One tablet per litre, wait 30 minutes. Cheap, light, keep for years.
- A personal filter straw removes bacteria and parasites including Crypto, but not viruses. Good for the bath or a butt.
Used together, or with boiling (one minute at a rolling boil does everything), they cover all of it. Boiling needs the camping stove.
Aquatabs ×50 in my kit adorOasis purification tablets ad Oasis purification tablets ad LifeStraw personal water filter in my kit ad
The bath trick
If you get a warning that the water is going off, fill the bath. A full bath is about 80 litres of flushing, washing and, treated, drinking water. A bath bladder keeps it clean and sealed; the WaterBOB holds up to 100 US gallons (about 380 litres), so a normal bath won't fill it. A plastic sheet over the top does half the job for free. Fill saucepans and the kettle too.
WaterBOB bath bladder in my kit ad
What the water company owes you
After 12 hours without supply, your water company must provide bottled water, 10 litres per person per day, usually from collection points in supermarket car parks. Customers on its Priority Services Register get it delivered to the door. In the January 2026 Thanet outage, Southern Water delivered to thousands of PSR homes while other customers used the collection points. Register anyone eligible: see the parents page. Compensation for long outages is paid automatically under the guaranteed standards scheme.
Storing it without it going green
- Cool, dark, off the floor, away from chemicals and fuel.
- Food-grade containers only (look for the cup-and-fork symbol); never old milk or squash bottles.
- Rotate bottled water yearly and stored tap water every six months.
- If stored water smells or looks cloudy, use it for flushing and treat or boil anything you drink.