How much water should you store? 3 litres or 10?

By SGWNI. Checked on 2 November 2026.

Store at least 3 litres of drinking water per person per day, for 3 days. That’s 9 litres each, and it’s what the UK government’s Be Ready campaign asks for. If you have the space, work towards about 10 litres per person per day, the British Red Cross figure that also covers basic cooking, washing and hygiene. The two numbers aren’t in conflict. They measure different things.

What each figure covers

The 10 litre figure for your own stored supply comes from the Red Cross, not the government. Be Ready says only that more would be needed for cooking and washing.

What that means for your household

A household of four needs 18 of the 2 L bottles to meet the 3 litre figure. Few people can store 120 litres, which is why the sensible steer is to get the drinking water done first.

Be Ready’s figure is per person, so count children too. The government’s 2026 survey found that only 4% of people had 3 days’ worth of water at 3 litres a day, and 82% had less than a day’s worth, so 9 litres each puts you well ahead.

Our water storage calculator works this out for your household, in bottles, including what you already have.

Why not one simple number?

Nobody has measured an exact minimum. The UK Health Security Agency reviewed the evidence on how much water people need in a disaster or a national power outage, and found nothing that answered the question conclusively. It noted that older people should have at least 1.6 litres of fluid a day to prevent dehydration. Reviews it looked at suggested 15 to 20 litres per person per day for drinking, cooking and cleaning, but it said this rested on low-quality evidence.

The UK Chief Medical Officers’ scripts for a national power cut say to try to drink at least 2 litres of fluid a day. So 3 litres gives a small margin for drinking, and it isn’t a precise line.

What your water company should do

If the mains supply fails, Ofwat says companies must provide at least 10 litres per person per day within the first 24 hours, and keep this going until the supply is back. Ofwat regulates water companies in England and Wales. They may do this with bottled water, bowsers or stand pipes.

That’s useful to know, but it doesn’t replace stored water. You may have to collect it, and it could take up to a day to arrive. If someone in your home is on the Priority Services Register, Be Ready says the company will arrange alternative supplies.

When you need more

• Baby formula. Keep extra water, or better, ready-to-feed formula. Be Ready says ready-to-feed is safest, and that bottled water is generally not recommended for making up powder.
• Medical devices. If a device needs water, ask your care team for a plan.
• Pets. No official source gives a volume. Be Ready says to store extra. Our calculator uses an estimate of 1 litre per pet per day, and a large dog may need more.
• Hot weather. UK sources give no figure. The US Ready.gov site says needs can double in very high temperatures.

How to store it

• Bottled water is the safest choice, says Be Ready. Keep it sealed, somewhere cool and dark, and follow the date on the label.
• If you fill your own containers, use clean, food-safe ones, and never one that has held chemicals such as fuel or paint. Change the water every 6 months. That timing comes from Ready.gov and the US CDC, because we found no UK figure.
• Spread it around. Several small bottles fit under beds and at the back of cupboards, where one big container won’t, and you can carry them.

Water for washing and flushing

Water for washing and flushing doesn’t have to come from your bottled supply. Be Ready says rainwater from a butt shouldn’t be drunk, but can be used for flushing toilets. Save bottled water for drinking, handwashing and preparing food.

If you run low, Be Ready says stored soft and fizzy drinks are safe to drink too. Don’t drink rainwater or stream water as it is. See how to make water safe for what to do if you’ve run out.