How much of your water is not for drinking?

The short answer

About half. The standard gallon per person per day covers drinking and cooking plus basic hygiene, and the hygiene half is the one people forget until they are rationing.

A single flush uses more water than you drink in a day

An older toilet uses around 1.6 gallons per flush, and plenty of pre-1990s ones use three or more. Your drinking requirement is about half a gallon a day. That arithmetic catches almost everyone out: a family of four flushing a handful of times a day can put more water down the toilet than the entire household drinks, and if the only water in the house is the clean supply you carefully stored, that is where it goes. This is the single most common way a sensible two week supply turns into a four day supply.

Keep a dirty tier, and fill it the moment you have warning

The fix is to have water you do not mind being unfit to drink. A filled bath holds around forty gallons. Buckets, cooking pots, a paddling pool and a rainwater butt all count. None of it needs to be clean, because flushing a toilet takes nothing more than a bucket of water poured briskly into the bowl, which triggers the siphon without touching the cistern. If a storm is forecast or an outage is announced, filling the bath is thirty seconds of work that protects the water you actually drink.

What the hygiene half really covers, in order of how much people miss it

Hands come first and most often, and hand washing is where a household quietly burns gallons. Then dishes, which you can nearly eliminate by eating off things you do not have to wash. Then teeth, faces and the sponge bath that becomes surprisingly important by about day four. Wet wipes and hand sanitiser are not a luxury here, they are water substitutes, and a large pack displaces several gallons of stored water for a fraction of the space.

Keep track of what you actually have.

Provision Planner counts the water already in your house against the target on this page, and tells you how many days you really cover.

See how many days you cover

The next questions, answered

Can I flush a toilet when the water is off?

Yes. Pour roughly a gallon and a half of water briskly into the bowl, not the cistern, and it will siphon and flush. The water does not need to be clean, which is why a filled bath or a few buckets are worth more than the same volume of drinking water.

How much water does hand washing use in an emergency?

More than almost anyone plans for, and it is the one you should not cut, since a stomach illness in a household with no running water is genuinely serious. Hand sanitiser and wet wipes are the sensible substitutes and they take up far less room than the water they replace.