First things first, where are you planning to travel? There are portable filters for practically any condition that you might come up against.

For example, if you are a hiker, drinking water straight from a spring or stream is unsafe. Ask any nurse working in an emergency room near the Appalachian Trail. Hikers come in all the time with a condition known as Giardiasis.

Hikers sometimes just call it giardia, the name of the single-celled parasite that causes the infection. So, if you expect to be in a situation where you will need to drink from a spring or stream, the best portable filters to carry with you will kill or remove giardia.

If you were traveling to Africa or other countries where the water source is particularly unreliable, the best portable water filters to choose will effectively eliminate water-borne diseases such as cholera. There are some excellent portable water filters on the market that are credited with reducing cases of potentially fatal diarrhea in Zimbabwe. Caused by drinking water contaminated with pathogenic bacteria and cysts, the condition is a common problem in Africa.

Let's face it. Most of us are not planning to take a missionary position and vacationing in a third world country is not particularly popular. But, all of us have to go to work, school, on vacation or somewhere with unfiltered tap water. While drinking it probably won't make us deathly ill, it could endanger our future health and it just doesn't taste good.

So, the best portable filters for the majority of people usually fall under the heading of sport bottle filters or water filter bottles. Different companies rearrange the words, but they all work similarly.

Typically, you will find plastic bottles shaped like any other sports bottle, but with a specially designed lid or spout that holds a filter. Some of these portable filters block only odor and chlorine. Others can remove giardia.

A few of the best portable water filters block lead, which is particularly important if you work or live in some of the major cities around the country. Recent reports have determined that the tap water in a large number of city structures is contaminated with lead, because of deteriorating pipes that carry water into the buildings. In other words, don't drink from the water fountain.

Make no mistake about it, portable water filters are a good alternative to buying bottled water. Not only will it save you money, but the quality and taste of the water will likely be better, particularly if you choose the best portable water filters. Plus, you'll be doing your part to help protect the environment from those ever growing piles of plastic bottles.