How Did I Know the Water I stored in Juice Bottles Was Safe to Drink?

On ProvidentLiving.org there is a section on how to safely store water.  

"If water comes directly from a good, pretreated source, then no additional purification is needed; otherwise, pretreat water before use. Store water in sturdy, leak-proof, breakage-resistant containers. Consider using plastic bottles commonly used for juices and soft drinks."

Using those instructions, I just wash out juice bottles and fill them with regular tap water.  Then I hide them all over my house.

When our water was out on Sunday-Monday, we used any bottles we found in the house to do washing, flushing toilets, etc.

But when I wanted to drink water, I used only the bottles from a certain room, because I knew I had only put them there in the past two months.

When a really big disaster happens, I plan to use our water filter to filter that small bit of water that we actually drink, just in case any of my stored water has any germs in it.  But the great majority of the water is actually used for washing and cleanliness, and the small chance of germs makes no difference there.

My advice for people who want to buy bottled water- only pay for the bare minimum of factory-bottled water.  Use free used bottles and tap water for the majority of the storage, there is no need to pay for that.