The general rule of thumb is that you’ll need one gallon of water per person per day. Half a gallon is used for drinking and the other half is used for hygiene. That number will go up depending on a whole host of factors. If you live in a hot climate or have pregnant or nursing women in your family, you’ll want to store more water.
Ok, so a gallon a day per person is the general rule.
Then the question becomes, how many days without water should you prep for?
Well, that depends on how prepared you want to be for varying degrees of scenarios or disasters.
It is recommended through certain agencies, that everyone have enough water to last three days should your regular water source be disrupted. Three days of water should be enough to get you through the periods of water shut-off.
Contamination can happen during natural disasters like earthquakes, major flooding and other disasters, so you will need some more. Three days is a good starting point, you can build on it from there.
Even though we don't have a lot of major disasters in the UK, around the world is a different matter. Water access can be down for much longer period than you think.
I have spent a considerable amount of time reading prepper blogs, sites and forums, it seems the general consensus is that you should have at least two weeks worth of water on hand. So for a single person, that’s 14 gallons of water. For a family of four, that would mean you’d need 56 gallons of water. That's a lot of water.
Whether you decide to go above and beyond the two-week minimum is up to you. For lots of people, finding space in their home or apartment to store enough water for two weeks is a stretch, so trying to find room for a month might not be the possible. Even if space isn’t an issue, the upfront costs for long-term water storage can be prohibitively expensive. Difference ways of sourcing are possible.
My recommendation would be to start off with the two-week supply and slowly build up to larger amounts as space and money become available.
Also, remember that this is for drinking and for your everyday needs too.
Small bottled water
You can get small bottles 500ml, normally in packs of 12. (6 litres) This would last one person,
one - two days.
Major bottles of water
These can come in 15 to 25 litres. One bottle of 25lt can last up to 5 days per person.
Larger bottles of water
Normally brought in bottles of 2lt, in packs of six. (12 litres) This would last one person just over three - four days.
These can come in anything from 30lt to 1000lt, depending on your space available.
Great for long term storage, depending on the conditions.
As with all water storage containers, they need to be stored where it is cool and out of direct sunlight. Unless it is the very large ones, which are designed to be stored outside. If not brought already sealed, fill bottles directly from the tap (tap water in the UK has chlorine added). Cap tightly and label each container with the words "Drinking Water" and the date stored. Store sealed containers in a dark, dry, and cool place. If after six months you have not used the stored water, empty it from the containers and repeat steps. If using a hose to fill up the larger ones, make sure you get one that is for this purpose only. Using your everyday garden hose will have contaminants in it. Thus would spoil your water.