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How much emergency water should you store?

For most UK households, the sensible answer is at least three days’ worth: around 2.5 to 3 litres of drinking water per person per day as a survival minimum, or about 10 litres per person per day if you also want to cover basic cooking and hygiene. A family of four planning for three days should therefore aim for roughly 36 litres at the minimum, or around 120 litres for a more comfortable supply, according to PreparedBritain’s guide to storing emergency water, which draws on GOV.UK, the British Red Cross and Ready Scotland.

Learning how to store emergency water properly is one of the cheapest and simplest preparedness steps you can take. Storms, burst mains and contamination alerts can cut the supply with little warning, and shops often sell out of bottled water within hours, as survival-kit.co.uk points out. This guide walks through the whole process: working out your household’s real needs, choosing containers, keeping water safe, treating questionable supplies and considering longer-term options.

Key takeaways

• Plan for at least 72 hours. GOV.UK’s Prepare campaign recommends being able to manage for at least three days; building towards a week is a sensible next step.
• Use 2.5 to 3 litres per person per day for drinking (the WHO survival minimum quoted by GOV.UK) and around 10 litres per person per day to also cover cooking and hygiene.
• Sealed supermarket bottled water is the cheapest, easiest option. Buy a few extra multipacks, keep them cool and dark, and rotate them before their best-before dates.
• Don’t forget pets and babies. Dogs and cats need roughly 50 millilitres per kilogram of body weight daily, and formula feeding needs clean water.
• Treatment options matter as much as storage. Boiling, filters and purification tablets let you use emergency sources safely if your stored supply runs out.

Why UK households need an emergency water supply

It is tempting to assume mains water will always be there, but recent UK events suggest otherwise. South West Water issued a boil water notice across Brixham and surrounding areas in May 2024 after Cryptosporidium contamination, affecting around 16,000 properties. Storm Babet flooded treatment works in eastern Scotland in October 2023. Burst mains and frozen pipes cause local outages every winter.

These events affected households that never considered themselves at risk. Water is the single most important resource in any emergency; people can survive weeks without food but only a few days without clean drinking water, as EmergencyKitLab UK notes in its water guide. A modest stored supply costs very little and needs almost no maintenance.

How much water to store for emergencies: a step-by-step calculation

There is no single figure that suits every household, because needs depend on the number of people, pets, climate and how long an interruption lasts. Follow these steps to work out your own number.

Step 1: Start with drinking water

UK Government emergency-planning guidance refers to a survival minimum of approximately 2.5 to 3 litres of drinking water per person per day. Heatwaves or heavy physical activity push that towards 3 litres or more; the July 2022 heatwave reached 40.3 °C at Coningsby, Lincolnshire, the UK’s first 40 °C reading, when dehydration was a genuine concern.

Step 2: Add cooking, washing and hygiene

Drinking water alone leaves nothing for anything else. A common planning figure is around 10 litres per person per day for all uses, covering drinking, cooking, washing up and basic hygiene. So one person for three days needs about 30 litres; a family of four needs around 120 litres, which amounts to little more than a few jerry cans under the stairs.

Step 3: Account for pets, children and special needs

Pets need their usual daily water too: roughly 50 millilitres per kilogram of body weight for a dog or cat. Babies on formula need clean water to prepare feeds, and children, nursing mothers and anyone unwell need more than the baseline. Older people often do not feel thirsty until they are already dehydrated, so build in a margin.

Step 4: Set your duration target

The British Red Cross and Ready Scotland suggest planning for three days. Once you have that covered, build towards a week as space allows; a family of four at the 3-litre drinking figure would need 84 litres of drinking water for seven days, or about 280 litres for all uses at 10 litres each per day. Tools like the emergency water storage calculator from Personal Preparedness can size this for your exact household, including pets and any water butts you already own.

Best emergency water storage containers for UK homes

You do not need specialist kit to start. Here are the main options, roughly in order of convenience.

Sealed bottled water (the easiest start)

Supermarket multipack bottled water is sealed, safe, date-stamped and costs pence per litre. Buy a couple of packs more than you would normally use, store them somewhere cool and dark away from direct sunlight, and rotate them through normal household use before their best-before dates. There is nothing to maintain and nothing to go wrong, which is why PreparedBritain calls it the cheapest way to build a reserve.

Jerry cans and larger containers

For bigger reserves, food-grade jerry cans and water carriers let you store 10 to 25 litres at a time in a garage, loft or under-stairs cupboard. Choose containers certified food-grade, clean them before filling and label them with the fill date. Remember that a full 25-litre container weighs around 25 kilograms, so split your supply into several smaller containers rather than one huge one you cannot move.

Water butts and rainwater

Water butts are useful for non-drinking purposes such as flushing toilets and cleaning. Rainwater should not be treated as drinking water unless it is properly filtered and purified, but as a hygiene reserve it extends your drinking supply considerably. We cover this in more depth in our guide to off-grid water for shed workshops.

What to avoid

• Containers that previously held milk, juice or chemicals; residues encourage bacterial growth and some plastics absorb contaminants permanently.
• Storing water in direct sunlight or near fuel, pesticides or strong-smelling chemicals, which can taint it through the plastic.
• One single large container; if it leaks or gets contaminated you lose everything.

How to keep stored water safe

Sealed, commercially bottled water needs nothing more than cool, dark storage and rotation before its best-before date. For water you fill yourself, a little care goes a long way.

• Use clean, food-grade containers and rinse them before filling with tap water.
• Fill from the cold mains tap, which is generally treated to a high standard in the UK.
• Label every container with the date it was filled and refresh the supply every six to twelve months by using and refilling it.
• Store away from heat, light and chemicals to protect both the water and the containers.

If stored water tastes flat when you come to use it, pouring it between two clean containers to aerate it usually improves the taste. Water that looks, smells or tastes wrong should be treated before drinking or used only for hygiene.

Water purification for your home emergency kit

Stored supplies can run out or become unusable, so every kit should include at least one way of treating water. Know your emergency sources too: the hot water cylinder tank, the cold water tank in the loft, and melted ice cubes from the freezer can all be used in a pinch.

Boiling

Boiling is the most reliable method: bring water to a rolling boil and let it cool before drinking. It kills pathogens but does nothing about chemical contamination, and it uses fuel you may also need for cooking and heat.

Filters

Portable filters and filter straws remove sediment and many pathogens, making them popular in emergency kits. Check the manufacturer’s specification for what a filter actually removes; not all deal with viruses or chemicals.

Purification tablets

Chlorine-based purification tablets are cheap, light and have a long shelf life, which makes them a sensible addition to any kit. Follow the packet instructions on dose and waiting time, and note that some parasites, such as Cryptosporidium, are resistant to chlorine at normal doses, which is exactly why the Brixham incident required a boil notice rather than a chemical fix.

Considering long-term water self-sufficiency?

Three days is the sensible starting point, and a week is a good target. Beyond that, some households start thinking about genuine self-sufficiency, whether that means bigger storage, rainwater harvesting or devices that produce water from the air.

One option readers sometimes ask about is the Water Freedom System, which the seller describes as an atmospheric water generator design, sometimes referred to as a water converter, that is intended to help households produce drinking water at home. According to the seller, it is a 2026 breakthrough aimed at long-term self-sufficiency.

We have not tested it, and the seller’s claims are their own; there is no independent evidence we can point to verifying performance or output. It is a digital product, so look carefully at exactly what is included and at the seller’s own guarantee terms before buying. It will most plausibly suit people who already have the basics covered, are comfortable with DIY construction projects and want to explore water generation as part of a wider self-sufficiency plan. If you simply want to be prepared for a burst main, sealed bottled water and a couple of jerry cans remain the better answer, and they cost a fraction as much. For broader off-grid projects, our guides to starting a self-sufficient garden are a low-cost place to begin.

Where to store your emergency water supply

Location matters as much as quantity. Choose somewhere cool, dark and frost-free, and spread the supply across more than one spot so a single leak, flood or collapse does not wipe you out.

• Under the stairs or in a hallway cupboard: accessible, temperature-stable and protected from light.
• A garage or shed corner: fine for larger containers, but check containers are rated for cold if frosts reach them, and keep them off fuel and chemical storage.
• Split across floors: if flooding or structural damage affects part of the house, some of your supply survives.
• Not the loft in summer: loft spaces get extremely hot, which degrades plastic and encourages any bacterial growth.

Whatever you store, check it once or twice a year: top up anything you have used, rotate anything nearing its date and confirm containers are still sealed and sound. Pair the annual check with another job, such as restocking the first aid kit or rebuilding your workbench, so it never gets forgotten.

FAQ

How long can you store tap water at home?

Tap water in clean, sealed, food-grade containers is generally considered fine for around six to twelve months if stored cool and dark. Rotate it regularly: use the old water for plants, cleaning or drinking and refill the containers with fresh supply.

How much water should a family of four store?

For three days, about 36 litres of drinking water at the 3-litre-per-person minimum, or around 120 litres if you also cover cooking and hygiene at 10 litres per person per day. For a week, those figures rise to roughly 84 and 280 litres respectively.

Do I need to add bleach to stored water?

Water filled from the UK mains into clean, food-grade containers does not normally need treatment before storage. Treatment is for water of unknown quality, such as from an emergency source. Never add household bleach containing fragrances or added cleaners, and follow official guidance on quantities if you do disinfect water.

Is rainwater safe to drink?

Not without treatment. Rainwater can carry contaminants from roofing, gutters and the atmosphere. Treat it as non-potable by default, useful for flushing toilets and cleaning, and only drink it after proper filtration and purification.

What should I do in a drought or hosepipe ban?

A drought is a different problem from a sudden outage: water may still flow, but restrictions apply. Stored bottled water still helps, and water butts let you harvest rain for the garden when mains use is restricted. PreparedBritain’s guide covers drought-specific advice drawn from official UK sources.

Final thoughts

Emergency water storage is the rare preparedness task that costs almost nothing and takes an afternoon. Work out your household’s figure, buy a few extra multipacks on your next shop, add a couple of food-grade jerry cans and a packet of purification tablets, and you have covered the single most important resource in any emergency. From there, whether you extend into rainwater harvesting, bigger reserves or atmospheric water generation is a matter of ambition rather than necessity.

Sources

• How to store emergency water at home, PreparedBritain
• Emergency Water Supply UK: How to Store & Treat Water · survival-kit.co.uk
• Emergency Water Guide – EmergencyKitLab UK
• Emergency Water Storage Calculator UK | How Much Water to Store