Water in the backcountry is much cleaner than what most people would expect, especially at high elevations, but even if the risk of infection is small, there is still a risk. Even experienced backpackers know it isn't always easy to find a good water source, and equip themselves with some kind of water treatment method.

A common reason people give for not treating their water is that they have been drinking it their whole life and so are immune to pathogens. This is not entirely true and more a testament to how rare infections are with experienced backpackers than anyone having a super-human immune system. For example, it is highly unlikely that you will ever become immune to Giardia, the most common water-borne pathogen in the backcountry. Giardia requires repeated infections to acquire any measure of immunity, and even then, your chance of carrying it without symptoms is less than 10%. You can get Giardia again and again and again.

Another reason I've heard, is that chemical treatments are more harmful. This is also not always true if proper chemical treatments are used correctly. This is also not a good argument for not taking a water filter.

I met four people who have contracted Giardia, and one person who got it twice. The consensus seems to be that the minor inconvenience of treating water is better than 2-4 weeks of nausea, fatigue, cramps, and the never-popular explosive diarrhea. Also, consider the fact that you're in the backcountry with no indoor plumbing and a limited toilet paper supply... Water treatment can be as lightweight as 1 ounce, as cheap as $1, and as small as a 1-ounce eyedropper of bleach, so it's worth taking.

1. They have a .1 micron filter... read more >
   
   A .1 micron filter will remove 99.99999% of protozoa/cysts, like Giardia and Cryptosporidium, and bacteria, like e.coli.
   
   
2. Multiple ways to use... read more >
   
   
   In addition to the water pouches that come with the Squeeze Filter, you can attach it to most threaded soda or water bottles including 2-liter bottles. This is how I usually use it. The 4-Way Filter Bottle can be attached to wide-mouth bottles like a Nalgene bottle. The 4-Way Filter, and the squeeze filter with the optional attachment, can also connect it to a hydration bladder hose and used as an inline filter.
   
   
3. Easy to use... read more >
   
   
   Fill up your pouch, bottle, or hydration bladder at the water source, attach the filter, and drink. No waiting, no pumping, and if you can reach your water container with your pack on, there's no need to take your pack off. This convenience means I'll stop more frequently for water, and carry less water weight.
   
   With both filters, you can also squeeze the water directly into a cook pot, unlike other filter straws.
   
   
4. Small and Lightweight. The Squeeze filter with a pouch weighs about 3 ounces, the 4-Way Bottle, about 5.
5. Sawyer has a one million gallon guarantee!... read more >
   
   
   I was skeptical, so I contacted Sawyer. Since most filters quit after a couple hundred gallons, this is essentially an attention-grabbing way of saying it has a lifetime guarantee on the filter element. The guarantee does not include the filter's housing or water pouches, which doesn't concern me since the filter has no moving parts, it's not that easy to break. Also, since the filters can be screwed onto soda bottles or Nalgene bottles, broken pouches or bottles are cheap fixes.
   
   
6. Easy to clean/backwash... read more >
   
   
   The Squeeze Filter comes with a syringe so you can easily backwash all the collected muck in the filter. This is one of the reasons it lasts for 1 million gallons. The 4-Way Bottle comes with a sink attachment to do the same.
   
   
7. Cons, because there is always one, right?... read more >
   
   
   The hollow fiber filter in Sawyer filters, can break if frozen, so if it is below freezing, you will want to keep it in your pocket during the day and in your sleeping bag at night. Damage from freezing is not covered under Sawyer's 1 million gallon guarantee. The worst of it is, you won't even know if it's not working. If you suspect it was frozen, you'll have to just throw it away.
   
   Some users have had problems with the water pouches that come with the Squeeze Filter ripping open. The pouches are holding up just fine for me so far, but I didn't purchase this filter for the pouches. And I prefer using plastic soda or water bottles anyway...  read more >

1. I carry 2-3 plastic water bottles. One 16 oz and one or two 32 oz. That way, I can lose or break a bottle and still have a way to transport water. A hiker with a dog came to my shelter on the Long Trail in Vermont, and the dog decided one of my water bottles was a fun chew toy. I'm glad I had a backup.
    
2. Plastic soda/water/gatorade bottles are free, lighter than Nalgene or aluminum bottles, and they are readily available and otherwise destined for a landfill. One argument I've heard for not reusing plastic soda bottles is that they release dioxins in your water. This is an urban legend. There are no dioxins in plastic soda bottles. That being said, a group of chemicals called phthalates are sometimes added to plastics to make them flexible and less brittle. These can leach into water if you heat up the plastic. I don't cook with them, so I'm not worried about this. (Reference)
   
   Another reason I've heard, for not reusing plastic soda bottles, is that bacteria can develop under the cap, but these get cleaned regularly during my bleach treatment, so I'm not concerned about that. If you know of any other reasons I shouldn't reuse soda bottles, please let me know at grayson.ryan@gmail.com.
    
3. Nalgene and other hard plastic or aluminum bottles cannot be squeezed to fill my cook pot with the Squeeze Filter. Or to get all the air out to treat the cap and threads when chemically treating the water.
    
4. I've never been a fan of hydration bladders, since they are difficult to get in and out of my backpack, hard to see how much water you have left, and not easy to attach to the outside of any of my packs.