Good replies so far. I would like to add a few things that haven't been mentioned. One is for people with multiple levels on their house. In the event of a water outage the water in the upper pipes can be drained to a lower level faucet. Put a collection bottle or bucket under a downstairs faucet. Open all the upstairs faucets, then open the downstairs faucet to fill the bottle or bucket. I keep a dozen or so gallons of potable water in bottles at all times plus some larger outdoor containers for rain water collection. I live within walking distance to a river. That would be a huge factor in a long term situation. We also have a cow pond that could be used if absolutely necessary. Eeew that sure wouldn't be fun.
I much prefer the Sawyer Squeeze
over the steri pens & lifestraws. No moving parts or batteries & very flexible in how they are used. I have a lifestraw & few other filtration devices but use the Squeezes extensively. They work very well & are almost unbreakable.
is an excellent technique to know.