For a prepper or a "self-reliant" person water is also a key question, both for drinking and hygiene.
I don't think it has a shelf-life so should store for a long time unless it gets contaminated. I also heard some plastics can release some unhealthy stuff into it after a while, it could worth look into it.
The key problem is a person needs a lot of it. We consume it not just by drinking, but it is used for cooking, soups to bread, many recipes needs it.
And then come the bubble baths so we can enjoy apocalypse properly. All right but even if you manage to use 1 liter warm water a piece of soap and a rag to clean yourself at every other day it still adds up large amounts on the long run. DON'T NEGLECT HYGIENE! It helps to keep you healthy, and easier to get grills in quarantine if you don't smell like a pig. Also feeling clean keeps up the morale too. Greasy hair feels awful, not to mention the sweat-and-dust sticking to your skin.
Oh and cleaning clothes, wash them, or if it is not possible at least hang them when the Sun shines, UV acts as disinfectant to some extent. Anyway washing clothes, cleaning plates and pots and kitchen appliances, all consumes water. You need a sea.
So the best would be a secure water source, a well is a good example. But you need a way to clean the water if it's not 100% sure it's clean. Could need filtering (charcoal is a good one), boiling (several minutes), or chemical purification. Also worth some investigation.