Work out your number
Plan for three litres per person per day for drinking and basic hygiene, for three days. A family of four therefore needs around 36 litres.
Store it properly
Use food-grade containers, keep them out of direct sunlight, and rotate the water every six months. A collapsible carrier stores flat until needed.
Have a backup
A filter bottle covers you if supply is contaminated. If in doubt, boiling water for one minute remains the most reliable household treatment.