Here is the Science behind it: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0089934
Basically you just gather together some pine branches, hollow them out a bit and pour water through them. This will clean out 99 percent of harmful bacteria and pathogens. If you do not have one yet you probably should buy a bug out bag. I am not trying to scare you or sound like a fear mongerer. However we do have nuclear threats all over the globe no matter your location. The earth herself is also a unpredictable force that is exhausted from being drilled into she is angry. It is better to be prepared and be able to move away from your home without having to pay high costs of hotels and what not. So I recommend at least having a backpack, tent, 2 weeks worth of GMO free organic vegan food, sleeping bag and extra clothes. Make sure its all packed so you can grab it within a second. You do not want to scurry around like a rat being chased like a cat if a huge earthquake happens.
I recommend having what you need until you can 1. build a safe shelter. 2. Walk to a safe location. You cannot depend on the stores or government officials to guarantee you a safe water source. Your life is YOUR responsibility. So take 20 minutes and start hollowing out some pine!