No. 2 · Water
Water: store it, find it, make it safe
In short: The government's Be Ready checklist says store 3 litres of drinking water per person per day for at least 3 days, with more for cooking and washing. For a longer outage, aim for 2 to 4 weeks of drinking water if you can, and have a way to treat more: bring water to a rolling boil and let it cool, or use purification tablets exactly as the label says.
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Why it matters
Water fails more often than power. In late November 2025 a treatment works failure near Tunbridge Wells cut tap water to up to 24,000 homes (around 60,000 people), and thousands were still without it five days later. The Drinking Water Inspectorate later found the water company fell short of its legal duty, which is to provide at least 10 litres of drinking water per person per day for the first five days of an outage, rising to 20 litres after that.
Ten litres a day from a bottled water station is the plan B. Your own store is plan A, because collecting it means queues, a car and fit people to carry it.
How much to store
- Government baseline: 3 litres per person per day for drinking, for 3 days (Be Ready). That's 36 litres for a household of four.
- For cooking and basic washing: the WHO puts survival needs at 2.5 to 3 litres a day and a basic total, including hygiene and cooking, at 7.5 to 15 litres.
- Our plan: 3 litres a person a day of drinking water for 2 to 4 weeks if space allows, plus non-drinking water for flushing and washing. Store what you can, then know how to treat more.
Use food-grade containers, keep them somewhere cool and dark, and label them with the date you filled them. Bottled water keeps until its best-before date; refill your own containers from the kitchen cold tap every six months or so.
Water already in your house
- Fill up early: at the first sign of trouble, while taps still run, fill clean containers, pans and the bath. Bath water is for flushing and washing, not drinking.
- Hot water cylinder: many homes have one holding roughly 120 to 210 litres. The Drinking Water Inspectorate says water from hot taps isn't recommended for drinking, so treat cylinder water before drinking it and use it first for washing.
- Loft cold water tank: the DWI warns that bathroom cold taps fed from a tank may not be suitable for drinking. Treat it as non-drinking water.
- Toilet cistern: 6 litres in a modern toilet, 9 litres in many pre-2001 ones (NI Water). Clean water for flushing or washing, but don't drink it.
- Water butt: Be Ready says rainwater can be used for flushing toilets, not for drinking.
Making water safe to drink
Boiling is the most reliable method. The Drinking Water Inspectorate's boil-water advice: bring water to a rolling boil, take it off the heat and let it cool naturally. Store boiled water in a clean, covered container, somewhere cool (the DWI says the fridge), and throw it away if it isn't used within 24 hours. If water is cloudy, let it settle and pour it through a clean cloth first.
Purification tablets (chlorine-based, sold at outdoor shops and pharmacies) are light and easy. Follow the pack exactly: dose depends on the tablet size and water volume, and most need around 30 minutes. Chlorine is weak against some parasites, such as Cryptosporidium, so boil if you can.
Filters (pump, bottle or straw types) remove bacteria and protozoa; check the manufacturer's claims, because many do not remove viruses. Filtering then boiling is the safest combination.
Neither boiling nor filtering makes chemically contaminated water safe. If the water might contain fuel, chemicals or floodwater, don't use it for drinking.
A note on household bleach
You'll see advice online, mostly American, to disinfect water with a few drops of plain bleach. There is no UK official guidance recommending it, and most UK supermarket bleaches are thickened or scented with additives that are not meant to be swallowed. We'd use boiling or proper purification tablets instead. Keep bleach for cleaning, especially toilets and bins.
Babies and vulnerable people
Be Ready advises keeping ready-to-feed baby formula, because you may not be able to boil water or sterilise bottles. If you have no choice but to use bottled water for powdered formula, Be Ready says use still water with no more than 200 mg/L sodium and 250 mg/L sulphate, boiled and cooled for no more than 30 minutes. If anyone in your home depends on water for medical reasons (dialysis at home, for example), tell your water company and join the Priority Services Register so they know to prioritise you.
Make water safe to drink by boiling
- If the water is cloudy, let it settle, then pour it through a clean cloth or coffee filter.
- Pour it into a clean pan or kettle.
- Bring it to a rolling boil, with large bubbles breaking the surface continuously.
- Take it off the heat and let it cool naturally with a lid on.
- Pour it into a clean, covered container.
- Throw away anything not used within 24 hours and boil a fresh batch.
Checklist
- 3 litres per person per day of drinking water, at least 3 days, building to 2 weeks or more
- Food-grade containers, dated
- Collapsible water carriers for collecting from a water station
- Purification tablets
- A portable water filter (optional)
- Camping stove, fuel and a pan or kettle for boiling
- Clean cloths or coffee filters for pre-filtering
- Ready-to-feed baby formula if you have a baby
- A water butt for flushing water
- Know where your stopcock is
Questions people ask
How much water should I store for an emergency in the UK?
The government's Be Ready checklist says 3 litres of drinking water per person per day for at least 3 days, with more needed for cooking and washing. For a longer outage, store more and have a way to treat extra water.
How long should I boil water to make it safe?
The Drinking Water Inspectorate says bring it to a rolling boil, then take it off the heat and let it cool naturally. Keep it covered and use it within 24 hours.
Can I drink water from my hot water cylinder or loft tank?
Not straight away. The Drinking Water Inspectorate says hot-tap water isn't recommended for drinking and tank-fed taps may not be suitable. Use it for washing, or boil it first if you have nothing else.
Can I use bleach to purify drinking water in the UK?
There's no UK official guidance recommending it, and most UK bleaches contain thickeners or scents. Boiling or chlorine purification tablets used as directed are safer choices.
What does the water company provide if my supply fails?
Under the water industry's emergency planning guidance, water companies must provide at least 10 litres of drinking water per person per day for the first five days, usually as bottled water stations, and 20 litres after that.
Sources: Be Ready checklist (PDF, October 2026) · Be Ready: water supply interruptions or outages · Drinking Water Inspectorate, receiving a boil water notice · Drinking Water Inspectorate, taste and odour in drinking water · Drinking Water Inspectorate, Tunbridge Wells loss of supply enforcement report (2026) · WHO Technical Note 9, how much water is needed in emergencies · NI Water, dual flush toilets · OSO Hot Water, what size hot water cylinder · CDC, how to make water safe in an emergency. General information only, not professional advice. In an emergency, always call 999.