When building your home kit you should have the maximum level of water filtration. In a bad emergency situation the water supply could get severely fouled. Most water filters remove contaminants down to 0.1 to 0.3 microns. Severely fouled water can contain viruses and other ultra small microorganisms that are smaller than this. For your home filter I recommend a 0.02 micron filter. These filters will start at about $140. If you are on a budget then consider one of these options:

• Purchase a personal filter such as a Sawyer Mini or Sawyer Squeeze. When you upgrade to a 0.02 filter then put the personal filter in your vehicle or hiking kit.
• Have a means of secondary treatment such as a UV purifier, purification tablets, or boiling.

Recommendation

I use a high-volume Sawyer Point ZeroTWO gravity filter for home use (about $140). This filter can attach to a faucet or to a filter bucket. I use it to remove hard water contaminants and to improve the taste of the water. This filter is not the best choice for backpacking since it is larger and normally requires buckets. The HUGE advantage of this filter is that it filters down to 0.02 microns whereas the more portable filters filter to 0.1 microns.