What The Guide Says

A store of emergency drinking water should be top of everybody's priority list. If a treatment plant fails, mains breaks or pipeline becomes contaminated, you will not be able to drink from the tap. Emergency responses are very stretched when this happens and it may be very difficult and take some time and effort for you to access safe drinking water. Storing water may seem intimidating, as it takes up a lot of space - and that is something that most of us are in short supply of in the UK, especially in urban areas.

By far the cheapest and easiest method of storing water in bulk is to buy some food-grade jerry cans and fill them up with tap water.

Filling food-grade jerry cans with tap water is a cheap and easy water storage method. Make sure to buy food-grade, BPA free - these are widely available at hardware stores and online retailers.

Here are some other methods to get and store water at home for emergencies:

Buy bottled water
Collect rainwater in a water butt with a lid
Invest in a water filter such as a Sawyer or British Berkefeld
Keep some water purification tablets stashed away (note that these are chemically based, unpleasant to taste and should only be used as a last resort).

Water butts can be used for a home rainwater harvesting system. This may be suitable if you have a garden, and is especially good for collecting greywater ^[*1], but is not necessary, so don't worry if you are unable to do this.

A popular survival field guide motto is "big bubbles, no troubles" - meaning water found in the wild that has been boiled is (relatively) safe to drink. However you might want to consider the difference between a mountain stream and your local river or canal!

Important

In general this guide tries not to be alarmist in tone, but here it is justified. In view of information learned from exercises and emergencies both in the UK and wider afield, you are very strongly urged to have a robust backup plan for drinking water. Unless disruption is local in area, external suppliers like water companies may not be reliable; furthermore, easily accessed surface water sources like reservoirs, lakes and rivers may be polluted and/or contested.

Rationale, background and more

Most of us are used to pure, drinkable water reliably available on demand from a tap. It is only when that water is no longer available that our critical dependency on water for survival becomes apparent. UK Government advice^[1] echoes what you will find in multiple online sources or printed survival guides: that a of 2.5-3 litres of drinking water per person per day is needed^[*2], whilst a realistic level is closer to 10 l/day to include cooking and basic hygiene needs.

Water supply interruptions should not be consigned to the 'imaginary fear' category. Residents of Tunbridge Wells experienced a lengthy supply disruption^[2] from 29th November to 12th December 2025, with severe impact on those affected. Widespread power outages (a popular topic in resilience literature) are broadly expected to result in rapid loss of water pressure in affected areas as water supplies typically depend on electric pumping. Exercises conducted by UK authorities tend to bear this out. It should be noted that if sewage pumping is interrupted and ground water sources become contaminated it may take considerable time before drinkable water supplies are restored^[*3].

UK Government publishes more detailed advice on preparing for water supply interruptions^[3] which should be noted including:

Water companies operate a Priority Services Register for qualifying individuals. If you are vulnerable or have specific needs, make use of it. In a severe emergency you may still have to fall back on your own resources, but if they don't know about you, they can't help.
If you or a member of your household rely on a medical device that needs water to function, talk to your care team to make a plan for what to do if there is a water outage.
Whilst there is no tap water, use alternative water supplies such as bottled water solely for drinking, washing your hands, cooking and preparing baby formula. There are other fluids which are safe to drink including soft and fizzy drinks that can be stored a cupboard. However do not drink milk or fresh fruit juice that smells as though it has gone off.
To prepare baby formula safely, you will need to be able to boil water and follow the normal safety procedures. If you are not able to boil water, please try to use ready-to-use baby formula. The NHS provides advice on making up baby formula^[4]. To wash your hands, fill a large bowl like a washing up bowl with water and add some soap or a household disinfectant. Keeping water usage to a minimum will prolong alternative sources of water such as water tanks.

Where possible you may wish to harvest rainwater in water butts. This is commonly considered to be 'grey water', not directly suitable for drinking unless boiled or chemically sterilised but useful for flushing toilets and non-food cleaning. There are numerous online resources advising how to do this, amongst them this from RSPB^[5] as one of many to choose from.

If you do experience a water shortage, bear in mind that toilet cisterns, where accessible, may represent valuable sources of drinkable water! Avoid flushing and emptying these to preserve their contents, especially if can use grey water for flushing.

Purifying Water For Consumption

Exactly how you choose to do this will depend on your source of water. Various online sources advise that contaminated water containing heavy metals or poisonous substances cannot reliably be made safe. If you have identified a preferred fall-back source of drinking water which you feel confident is free of such contamination, locate and print suitable guidance on rendering it safe. A useful source is the American Environment Protection Agency Guidance^[6] which also comes in a printable pdf form.

Generally speaking your options for water purification will be one or more of

Boiling
Chemical sterilisation using tablets, household bleach^[7] or granulated calcium hypochlorite which can be turned into bleach - often being sold under the name 'Pool Shock' for swimming pools. Calcium hypochlorite is extremely concentrated and a small amount could be shared amongst numerous neighbours.
Use of biological filtration such as used by hikers (suggested search term: 'hiking water filter') or whole-of-house systems (suggested search term 'household biological water purification system'). Check that the chosen solution guards against water-borne diseases like cryptosporidiumm and giardia.

UK Government advice on sterilising with bleach is worth repeating in full here^[7]

If you have run out of safe fluids, there are other sources of water you can drink as long as you take some additional steps to make them safer. This includes water from hot water taps. You can also drink rainwater [or melted snow or ice in season] and water from water butts. Water from reservoirs, fresh-water lakes and free flowing streams can also be made safer to drink. I know not everyone will live close to these sources and so you should only access them if you live very close by and can get water from them safely. River water is much less safe to drink and you should only drink river water as a last resort. These are the steps you should take to make this water safer:

Use a clean container to collect the water. Do not use a container that used to hold chemicals such as fuel or paint.

Once the container is full, check that the water looks clean. If there is an oily film on top, don't drink it.

Get something to filter the water - a coffee filter, pillowcase or bedsheet

Pour the clean looking water through the filter material and then throw away any solid bits in the filter. Repeat this until the water runs clear.

If you can, disinfect the filtered water by boiling it or by using water purification tablets as long as they are in date.

If you can't boil the water and you don't have purification tablets, you can use regular household bleach, ideally unscented. It is important not to use too much bleach. Add approximately one-quarter of a teaspoon of unscented, household bleach for every 10 litres of water (approximately one bucket). Leave it to stand for 15 minutes.

The water should have a slight chlorine smell. If the smell is very strong, leave it uncovered for 2 hours before drinking.

Store your water in a cool, dark place.

This water should be used for drinking rather than washing your hands or cooking.

References

^{^} UK Government 'Get Prepared' advice
^{^} Wikipedia entry on Tunbridge Wells water disruption in 2025
^{^} UK Government advice on water supply interruptions
^{^} NHS guidances on making up baby formula
^{^} RSPB advice on installing a water butt
^{^} EPA Guidance on Water Purification
^{^} UK Government Scripts to be read out in case of national emergency

Footnotes

^{^} Grey water is a term used for water not pure enough for drinking purposes but potentially useful for flushing toilets and external washing
^{^} Multiple online sources note that more than 2 l/day may be needed for personal consumption in hot or humid climates.
^{^} Found from AI search for 'if a wide power outage interrupts sewage pumping, does this affect the restoration of drinking water?', also inside information gained from official exercises (no official source available).