Well, I have nearly everything, but our little pen thing broke (which purifies water), so back to the drawing board for something. It is a confusing topic but outdoorgearlab.com has some good advice. There are three kinds of systems: filter, chemical and UV. The net is that a filter doesn't take care of viruses, but they are not in the US much (although I know plenty of people who have gotten it, so personally I'd carry either the chemical or the UV as well as the filter, but that is just me. Aquamira is light, but you better get used to adding in Tang as it tastes yucky. The UV light is good for short trips and doesn't add taste. Net, net, for short trips what makes the most sense is UV pen for personal and a filter at base camp.
In terms of what to pick, here are some thoughts
- Sawyer Squeeze Water Filter. This is a squeeze bottle and is cheap. It is good for a million gallons (it says!) and is for fewer people. Hikelighter.com likes the Pointone Squeeze Water Filter. They do recommend backflush every 5-10 gallons. Right for a small camp for a few days. Hikelighter.com has lots of thoughts. The Everynew water bags are better than the original Sawyer bag, but the latest Sawyer bag is apparently very durable (at 9 ply vs 4 ply). Also don't let the thing freeze as this will blow out the hollow fiber filter. Interesting to see Amazon has it for $40 (Sawyer SP131 PointOne Squeeze Water Filter System with Three Pouches). It is $50 (pre-rebate) at REI. You also want the SP110 that lets you connect it to a hydration bag for gravity feed (Sawyer Inline Hydration Pack Adapter for Screw On Filter). It also won the Backpaker Magazine 2012 Editors' Choice.
- Steripen. Despite the fact that mine broke, this seems the easiest way to be 100% safe. Good for personal use. Heck, I want to use it when I go to China. Main issue is reliability of the sensor which was fixed in later generations. Sadly, mine had a bad sensor. The original SteriPEN Adventurer Opti is 3.7 ounces $75 from Amazon (SteriPEN Adventurer Opti Handheld UV Water Purifier) but the new Steripen Freedom uses a rechargeable Li-Ion battery vs CR123 batteries and weighs just 2.7 ouncs. So if you have a USB power source or a solar panel, you are realy in luck. At amazon for $100 (SteriPEN Freedom Water Purifier)
- Katadyn Micropur or Aquamira. This is like Iodine but Brett says it doesn't have a bad taste. This is Chlorine Dioxide which takes just 20 minutes rather than hours and to some tastes better than the Iodine used in Aquamira (as long as the water is cold). Also micropur needs 4 hours against protozoa and Iodine doesn't work against protozoa. $12 from Amazon Aquamira Water Treatment Drops 1oz
Here is some background
How to Choose the Best Backpacking Water Purification - OutdoorGearLab
UV Purifiers: Effective against all pathogens: bacteria, viruses, and protozoa. UV treatments do not actually kill pathogens, they simply scramble the DNA of the organisms so that they cannot reproduce. Be careful of treating water and then letting it sit in visible light for a long period of time, because the organisms can reactivate. Does not strain out particulate unless you use a pre-filter. Does not change taste of water [but doesn't filter]
For the average hiker in the US, we suggest a filter, either gravity-fed like the Playpus Gravityworks or a pump like the MSR Sweetwater, because these are effective without being too heavy and also do no involve adding chemicals to your water and your body.
If you are a single hiker on a short trip, then this is not a huge concern. Scooping water into your Nalgene and treating with a SteriPEN will work just fine. However, if you are bringing one treatment method for a group of people, or you want the ability to treat a lot of water for cooking at base camp
If you are shopping for a filter, a techy detail that you will continually stumble across is micron size. This is a measurement of the pore size in the filter media. Essentially, the smaller the pore size, the more pathogens the filter can strain out. A simple rule of thumb is that the smallest bacteria is 0.2 microns, so a filter should be around that size or smaller to be the most effective.
If you are an ultralight backpacker, then use the Aquamira chemical treatment. It is tiny and take your chances with viruses 🙂
If you have chosen a pump filter as your treatment method, and you plan to bring it with you on multi-day trips, it is important that you look for a pump that is field maintainable, meaning you can service it on your own in the back-country if it gets clogged. For example, ceramic filters need to be scraped relatively often, but this is easy to do. Most other pump-filters are engineered to be easy to back-flush to remove clogs, but it is worth investigating how complicated this process will be so you don't get left high and dry on your over-nighter.
Viruses: Examples include Hepatitis A and rotovirus. Viruses are not thought to be a large threat when hiking and traveling in the US and Canada, but on other international trips viruses become a much larger concern. Viruses are extremely small, so are not strained out with most filters.
This reminds me that this is like a camelbak and I need another cleaning tablets and a cleaning thingy. So time for a camelbak upgrade. Maybe move to Platypus?
And here is what backpacker.com says, they like the Steripen and the MSR Hyperflow, but don't mention it requires a backflush every eight liters!