I've always stored water as
A) I have complex medical issues which means I can't drink tap water
B) There have been several times where we have had water problems
There is nothing worse than the water board knocking at your door at night saying there is a leak and you have 5 minutes to fill a kettle / sink / bath before they turn the water off. Except every single time, the water is already sludge brown or it's been turned off as the fella has been knocking on doors.
I buy the 3 litre ones from Sainsbury's (were 17 a month or so ago, then 25p, now 29p) I always have a bottle in the fridge for drinking, and 6 bottles under the bed. I don't like the idea of larger ones as I'm disabled and they would be cumbersome. (although I like the sound of a tap!) Anyway, I make sure to rotate date wise often. If I screw up, then any out of date ones get stored in the conservatory and would be used to flush the bog in any water outage situationn.or like a PP, water some plants.
Our water was once off for a week and the promise of dropping off drinking water took some time. It was also limited to 2 bottles per house per day, so we had to use a bucket and a stand pipe in the next street for toilet flushing water etc. This was many years ago, but it was January, and it stayed with me.