It's good to store a pack for cases of emergency. Even things like a broken supply water pipe on a hot sunday can be harsh, let alone local pollution warnings t

It's good to store a pack for cases of emergency. Even things like a broken supply water pipe on a hot sunday can be harsh, let alone local pollution warnings that last half a day or more. Storing the tap water itself is a lot harder since you need to keep it clean enough nothing grows in there for a while; bottled water is very convenient.