Boiling is great on filtered water, as it kills most of the bacteria. It does nothing for chemicals, so you still need to choose your water source carefully.
I also have a SteriPen but haven't used it yet. For my house, I also have an Ecoloblue, which is an atmospheric Water Generator. It makes pure water from the air by drawing out the humidity, filtering it, purifying it and storing it for you. It is the best tasting water that I've ever had. Here is the site:
http://www.ecoloblue.com/. It works very well in humid summers, not so well in the winter. It uses UV like the Steripen. It can connect to one of my solar panels for power when the grid is down.
Another option is using small amounts of bleach or iodine to purify water. These make the water taste bad and can only be used for a short while. They'll send you to the bathroom if you use them too much.
There are many ways to filter, including using a plain old bandana to get the big stuff, even charcoal to get the small stuff. A YouTube search can send you in the right direction.
