Water is the single most important thing you could have during a survival situation – you know this because we keep beating you over the head with it. The importance of this live giving fluid cannot be overstated. Naturally occurring water that is safe to drink is a virtual rarity; it does exist in some parts of the world, but the simple fact is that 98% of water is not safe to drink without some sort of treatment or filtration, and thus we must assume that all water is therefore unsafe.
If we should happen to find ourselves at home when the next survival situation strikes, whether by happenstance or just choosing to bug in, we have many options for water filtration as well as the tools to filter or purify water. Being stationary does have many advantages, and besides our water stockpile, we will most likely have bleach, filters, and other gear with which to filter water.