How to make water safe to drink when the taps stop

Order of choice

1. Bottled water and other safe drinks. Be Ready says bottled water is the safest way to prepare, and recommends 3 litres per person per day for 3 days. The UK Chief Medical Officers (CMOs) add that soft and fizzy drinks and juice from tinned fruit are safe too, but not milk or fresh juice that smells off.
2. Water from your company. Check your water company's website for bottled water stations. If you're on its Priority Services Register, it will arrange water for you (Be Ready).
3. Water you make safer yourself: collect, filter, then disinfect by boiling, tablets or, as a last resort, bleach.

While supplies are short, the CMOs say use water only for drinking, washing hands and preparing food.

How much you need

• Store: 3 litres per person per day for 3 days (Be Ready), plus extra for babies, pets and medical devices.
• Drink: the CMOs say at least 2 litres of fluid a day, about 8 cups. Children under 2 who aren't breastfed need at least 1 litre a day, about 4 cups; formula milk counts towards this.

Step 1: Collect the cleanest water you can

The CMOs list these sources, once made safer:

• water from hot water taps
• rainwater, and water from water butts
• reservoirs, fresh-water lakes and free-flowing streams, but only if you live very close and can reach them safely
• river water only as a last resort

Use a clean container, never one that held chemicals such as fuel or paint. Be Ready says water butt water isn't for drinking as it stands, as it could contain bacteria, so always treat it.

Step 2: Filter it

Pour the water through a coffee filter, pillowcase or bedsheet, throw away the bits, and repeat until it runs clear (CMOs). Be Ready says most water from other sources needs filtering before you use tablets. If there's an oily film on top, don't drink it at all.

A camping water filter can help with this step. Read what the maker says it removes, and still boil or use tablets unless the label says the filter is enough on its own.

Step 3: Disinfect it

Boiling (best if you can)

The Drinking Water Inspectorate (DWI) says:

• bring the water to a rolling boil, take it off the heat and let it cool naturally;
• keep it in a clean container in the fridge;
• throw it away if it isn't used within 24 hours;
• take care: boiling water scalds.

If you're boiling on a camping stove or barbecue, do it outdoors. Using them indoors risks carbon monoxide poisoning. Our post on keeping warm without power explains why.

Purification tablets

Be Ready says follow the instructions on the label, because tablets come in different strengths, and filter the water first. Check the use-by date: the CMOs say only use tablets that are in date.

Bleach: last resort only

If you can't boil water and have no tablets, the CMOs give this method:

• Use regular household bleach, ideally unscented.
• Add about a quarter of a teaspoon for every 10 litres of water (roughly a bucket). Don't use more.
• Leave it to stand for 15 minutes.
• It should smell slightly of chlorine. If the smell is very strong, leave it uncovered for 2 hours before drinking.
• Use this water for drinking, not for washing hands or cooking. Store it somewhere cool and dark.

This comes from public health scripts the four UK CMOs published in December 2025 for a national power cut. They aren't government policy, but they are the UK's official medical advice for that situation, and the only UK bleach dose we've found. Measure carefully, keep bleach away from children, and boil or use tablets instead whenever you can.

Water you should never drink

• Floodwater. It may contain sewage and hide rubbish (Be Ready), and the CMOs say don't use it for drinking.
• Water with an oily film, or in a container that held fuel, paint or chemicals (CMOs).

A boil water notice is different

If your water company issues a boil water notice, the tap water still flows but may contain germs. The DWI says boil it before drinking, brushing teeth, making ice, preparing food, cleaning feeding equipment or giving it to pets. You can still shower (keep it out of your mouth), wash clothes and flush as normal. A rarer "do not use" notice means drink bottled water or the supply your water company provides.

Babies

Be Ready says ready-made or ready-to-feed formula is safest when you can't boil water. Bottled water isn't usually recommended for formula, but in an emergency you can use still bottled water with no more than 200 mg/L sodium and 250 mg/L sulphate on the label, boiled and cooled for no more than 30 minutes.

Washing hands with little water

The CMOs suggest one large bowl of water with soap or household disinfectant for the whole household to wash hands in, kept going for the whole outage. Use a separate bowl for anyone with diarrhoea.

Related guides

• No water supply: what to do, and what you're entitled to
• Boil water notice: what it means and what to do
• Emergency water at home: how much to store and how
• Hosepipe bans: what they mean, and how to check if one applies to you

Free tools

• No water in my area: your water company's live page
• Emergency supplies calculator (how much water to keep)
• Priority Services Register checker

We're an independent UK site, not the government. We check guides against official sources and link to them. In an emergency call 999.

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