Water

The page above gives the figure and the kit. This is the part underneath it: what the figure means, where it stops being true, and the decisions it does not make for you.

What 4 litres actually buys

4 litres per person per day is a survival ration, not a living ration. It is the right number to plan the emergency store around, and it is worth being clear about what it is buying, because the gap between surviving and living on it is where households come unstuck in the second week rather than the second day.

The humanitarian standard for people in camps, which is the closest well-studied comparison to a household with no mains, is 15 litres per person per day covering drinking, cooking and personal hygiene. Of that, drinking and food account for 2.5 to 3 litres and basic hygiene for 2 to 6 litres. Below about 5 litres a day, the assessment is that hygiene cannot be assured at all.

So the 4 litre figure is honest about the store and quiet about the consequence. Two weeks at 4 litres means two weeks of no laundry, no proper washing, and hand hygiene done from a cup. That is survivable and it is also the exact condition in which the sanitation and skin problems in the medical domain start.

Plan the store at 4, plan the supply at 10. The store is what you buy and stack now; the supply is rainwater, a filter and a route to more. They are different problems and the single figure hides that.

Who needs more than the headline

The number is a household average, and averages are the wrong tool for the people most at risk.

• Anyone with vomiting or diarrhoea needs considerably more, and needs it as small sips continuously rather than as a volume. This is the commonest way a household emergency turns medical.
• Anyone with a fever. Fluid loss rises with temperature.
• Pregnant and breastfeeding women. Breastfeeding in particular adds a real daily requirement, and it is the one nobody plans for.
• Small children, who dehydrate faster than adults from the same illness because they hold less to begin with.
• Older people, whose thirst sensation is less reliable, so waiting until they ask is waiting too long.
• Anyone doing hard physical work, which in a crisis means whoever is carrying, digging or clearing.

The first hour

The parent page is written for a household that has prepared. This section is for the one that has not, or that has and is now watching it happen.

The moment there is any reason to think the supply is at risk, fill everything. Mains pressure is not yours to keep. You do not control the interval between a problem starting and the taps stopping, and it is routinely shorter than people expect.

1. The bath, with a bladder if you have one and without if you do not. A bath holds more than every bottle in the house put together.
2. Every pan, kettle, jug, bucket and clean bin. Cover them.
3. The washing machine and dishwasher are not water stores. Do not count them.
4. Fill the kettle last and boil it, so you have sterile water without spending fuel later.
5. Stop flushing on every use. One flush is 6 to 9 litres, which is more than a person's whole daily drinking ration going into the sewer.

Then turn off the incoming stop tap if there is any chance of contamination in the mains, such as a burst main nearby or a boil-water notice, so the pipework you have just filled does not draw in whatever is in the street.

Water already in the system is yours. The cold pipes drain from the lowest tap in the house, and there may be a good deal of it. The hot water cylinder, if you have one, holds a large volume and is a job for an adult who knows where the drain cock is and has turned the immersion off first.

What fails first is not thirst

Households plan for thirst. Thirst is not what stops them.

Sanitation fails first, because the toilet is the largest single consumer of water in the house and the first thing to become unusable. The twin-bucket system exists for exactly this, and the reason it appears in the sanitation domain rather than here is that it is a waste problem, not a water problem. Solving it removes the biggest draw on the store at a stroke.

Then hand washing, which is the point at which a water shortage becomes an illness. It is also the one people economise on first, because it feels like the least urgent use.

Then cooking, which quietly assumes water you had planned to drink: dried pulses, rice and pasta all need volume, and the water used to cook them is not wasted if you keep it.

Then morale. Being unwashed for a fortnight in a cold house does something to a household that no chart shows, and a strip wash from a bowl of warm water is worth more than its litres.

Running a rotation that does not lapse

The parent page says rotate every 6 to 12 months. The honest problem with that instruction is that it is a chore with no deadline, which is the kind that does not get done.

What is actually happening in the container. Tap water arrives chlorinated. Sealed in a clean, opaque, food-grade container, kept cool and dark, there is nothing in there to feed anything. It does not go off the way food does. What degrades is the residual disinfectant, the taste, and eventually the container itself, and light is what turns a stored bottle green.

Make it a date, not a duty. The rotation that survives is the one attached to something that already happens: the clocks changing, twice a year, is the standard trick and it works. Empty onto the garden, rinse, refill, done in twenty minutes for a household store.

Label every container with the date it was filled, in pen on tape. An unlabelled store is one nobody trusts, and water nobody trusts gets thrown away and replaced far more often than it needs to be.

Working out your own number

Multiply out your own household rather than accepting the per person figure, because the answer changes what you buy.

Days x people x litres. Two adults and two children for two weeks at 4 litres is 224 litres, which is eleven 20 litre containers and takes up more floor than most people picture. At 10 litres it is 560 litres, which is not a stack of jerry cans at all, it is a tank and a way of refilling it.

That is the real decision this page exists to force. A fortnight of stored water is a shopping trip. Anything beyond a fortnight is not storage, it is supply: a rainwater system, a filter, and a source you have already identified and walked to.

The tools section will do the arithmetic for you, including roof area against local rainfall, at the rainwater calculator and the water planner.