Storing water without contaminating it
Most household contamination happens after collection, during storage and handling.
The risk is in the handling
Water that was safe when collected often becomes unsafe in the home. The usual route is a hand, a dipper or a cup entering an open container.
Container choice
Use food-grade containers with a narrow mouth, a tight lid, and ideally a tap. A narrow opening keeps hands and utensils out. If you only have wide-mouthed containers, use a dedicated long-handled dipper that is never put down on the floor and never used for anything else.
Never store drinking water in containers that previously held fuel, pesticide, paint, bleach or any other chemical. The residue is not removed by rinsing.
Keep containers off the floor, out of direct sunlight, and away from animals and toilets. Sunlight encourages algae growth in translucent containers.
Cleaning
Wash containers with soap and clean water, rinse, then let them dry completely before refilling. Clean the lid and the tap too, since these are handled constantly.
How long stored water keeps
Properly treated water in a sealed, clean, opaque container kept out of the heat stays usable for months. In practice, rotate household storage every few weeks so you are always drinking recent water and you find out about a cracked container before an emergency rather than during one.
If stored water develops a smell, a film, visible growth or cloudiness, do not drink it.
Sources
This guidance is general information, not medical or engineering advice for your specific situation. Boiling does not remove chemical contamination, and no single household treatment method handles every contaminant. Follow instructions from your local health office and water utility.