Prices and specs last checked by Look Into on 23 October 2026 · next check 18 December 2026 · how we picked
The short answer
- How much: the government's Be Ready checklist says 3 litres per person per day for drinking, plus extra for cooking and washing, for three days. That is 9 litres each, or 36 litres for a household of four.
- Cheapest way to buy it: Sainsbury's own-brand 6 x 2 litre spring water was £3.00 for 12 litres on 23 October 2026 (25p a litre). One pack covers one person; three packs (£9.00) cover four people.
- Cheapest way to store tap water: a collapsible 20 litre carrier from Argos (Regatta, £9.00) costs 45p per litre of capacity, and the water itself comes from your tap. Two cover a family of four.
- Bottled is simpler. Be Ready asks for bottled water, it carries a best-before date, and there is no container to clean.
The arithmetic
| Household | Drinking water for 3 days | Sainsbury's 6 x 2L packs needed | Cost, 23 Oct 2026 |
|---|---|---|---|
| 1 person | 9 litres | 1 (12 litres) | £3.00 |
| 2 people | 18 litres | 2 (24 litres) | £6.00 |
| 4 people | 36 litres | 3 (36 litres) | £9.00 |
| 6 people | 54 litres | 5 (60 litres) | £15.00 |
Working: people × 3 litres × 3 days, rounded up to whole 12-litre packs at £3.00 each. This is drinking water only; Be Ready says to allow more for cooking and washing.
Bottled water: what 9 litres costs by brand
Priced at Sainsbury's on 23 October 2026, buying whole packs to reach at least 9 litres:
| Water | Pack | Packs for 9L | Cost for 9L+ | Per litre |
|---|---|---|---|---|
| Sainsbury's Spring Water | 6 x 2L, £3.00 | 1 | £3.00 | 25p |
| Sainsbury's Still Spring Water | 5L, £1.75 | 2 | £3.50 | 35p |
| Highland Spring | 6 x 1.5L, £3.95 | 1 | £3.95 | 44p |
| Sainsbury's Spring Water | 2L, £0.95 | 5 | £4.75 | 48p |
| Volvic | 6 x 1.5L, £4.85 | 1 | £4.85 | 54p |
| Sainsbury's Spring Water | 12 x 500ml, £2.50 | 2 | £5.00 | 42p |
| Evian | 6 x 1.5L, £6.00 | 1 | £6.00 | 67p |
| Evian | 12 x 330ml, £4.75 | 3 | £14.25 | £1.20 |
The same 9 litres costs £3.00 or £14.25 depending on the bottle. Big bottles are cheapest per litre; small ones are handier to carry if you have to leave home.
Storing tap water instead
If you have the space, tap water in a food-safe container is the cheapest long-run option. Containers priced on 23 October 2026:
| Container | Where | Capacity | Cost per litre of capacity | Type |
|---|---|---|---|---|
| Regatta 20L Foldable Water Carrier | Argos, £9.00 | 20L | 45p | Collapsible, with tap |
| ShopMazo 2 x 25L jerry cans | Amazon | 50L | about 47p | Rigid HDPE, listed as food contact approved |
| 20L collapsible container with tap | Amazon | 20L | about 49p | Collapsible LDPE, BPA free |
| Cedilis 2 x 20L collapsible | Amazon | 40L | about 50p | Collapsible LDPE, BPA free |
| UK GROW 25L jerrycan | Amazon | 25L | about 52p | Rigid HDPE, listed as food contact approved |
| ITP Packaging 2 x 20L | Amazon | 40L | about 62p | Rigid HDPE, for potable water |
| Leisurewize 51L roller carrier | Argos, £55.00 | 51L | £1.08 | Rigid, wheeled |
| Vango 10L Jerrycan | Argos, £22.00 | 10L | £2.20 | Rigid HDPE, BPA free |
Amazon prices change often; check the live price on Amazon. Per-litre figures are from the price read on 23 October 2026.
Watch the labelling. One 25 litre jerry can sold as "food grade" lists its product type as "liquid fuel container" on the same page. Several rigid cans are described as UN approved for hazardous liquids. For drinking water, choose a container its seller describes as food contact approved or for potable water, and never reuse a can that has held anything else.
How often to refresh it. We found no UK government guidance on how long home-stored tap water keeps. The US Centers for Disease Control and Prevention advises using food-grade containers and replacing stored water every six months. Be Ready asks households to check their kit every six months, so the same rhythm works.
Bottles or containers?
| Bottled water | Tap water in containers | |
|---|---|---|
| Cost for a family of four (36L) | £9.00 (3 x Sainsbury's 6 x 2L) | £18.00 for two Regatta 20L carriers, then tap water |
| Refresh | By the best-before date | Every six months (CDC guidance) |
| Effort | None | Clean, fill, label, empty and refill |
| Carry if you leave home | Easy in small bottles | 20 litres weighs about 20kg |
On these prices, bottled water costs less up front for a family of four (£9.00 against £18.00). The containers pay for themselves once you would otherwise have bought the bottled water twice.
Purification tablets: a backup, not a plan
Oasis tablets on Amazon state that one 67mg tablet treats 10 litres, so a 200-tablet pack treats 2,000 litres. That is useful if mains water is cut and you must treat water from another source, but follow the instructions on the pack and keep bottled water as your first supply.
Live Amazon prices
The table below pulls live prices from Amazon's own feed, which can differ from the Amazon buy box. Not in it: the 20L collapsible container with tap, which Amazon's product feed does not return (its Amazon link in the table above still works).
Prices in this table come from Amazon and are refreshed at least once a day, with the date of the last update under the table. The cost-per-use and running-cost figures on this page use prices Look Into read on 23 October 2026, so they can differ from today's price.
As an Amazon Associate, Look Into earns from qualifying purchases. Product prices and availability are accurate as of 23 October 2026 and are subject to change.
Questions people ask
How much water per person per day in an emergency? Be Ready says 3 litres per person per day for drinking, plus more for cooking and washing.
Can I just fill bottles from the tap? Yes, in clean, food-safe containers. Refresh them regularly; the US CDC advises every six months.
Does bottled water go off? Bottled water carries a best-before date. Check it when you check your kit.
Should I store water for pets? Be Ready lists pet food and bottled water for pets.
Sources
- Be Ready checklist (GOV.UK campaign), read 23 October 2026.
- US Centers for Disease Control and Prevention: creating and storing an emergency water supply, read 23 October 2026.
- Sainsbury's, Argos and Amazon UK product listings, read 23 October 2026 (URLs in the source register).
What this guide could not check
- Whether any container meets food-contact rules; we relied on the listing.
- How long tap water keeps in each container type; the six-month figure is US guidance.
- Best-before dates on the bottled water.
- Container weights; the roughly 20kg for 20 litres is the water alone.