Purifying Water

Water Purifiers are required to "remove, kill or inactivate all types of disease-causing microorganisms from the water, including bacteria, viruses and protozoan cysts so as to render the processed water safe for drinking." - according to the EPA standards.

Both portable water filters and purifiers operate on the same mechanical principle. They suck up raw water from a contaminated water source and force it through a filtering medium to trap impurities - everything from sediment to invisible microorganisms. The clean water is then dispensed for use.
The difference between a water purifier and a water filter is that a purifier removes viruses(0.01 microns), as well as the bacteria(0.1 micron) and protozoa(1 micron) that filters can remove. Viruses wee too darn tiny to be removed with a filter so many purifiers use either chemicals like iodine to kill viruses or an electro-static charge to capture them. Technology now allows filtering membranes to remove viruses down to 0.02 microns without chemical or electro treatment.

Lots of dudes will say that there is not much risk from viral infection in North America, but if you go abroad, then you have to be more careful. And, historically, to get rid of viral contamination in water, it was difficult, time-consuming, and expensive - but, hey, that's been changing! So, if you can get rid of everything and it doesn't cost much more and is not a real big hassle, then you might as well do it, right?

There are now quite a few water filters that add on a chemical treatment to kill viruses - presto, a water purifier! And, the new breed of personal water purifiers that look just like soccer water bottles do a great job for individual use. But, they aren't too great for a backpacking crew.

You now have 4 options to purify your water while backpacking or hiking:

Purifier Criteria

Absolute Pore Size: A purifier will have a pore size rating in its advertising literature. A general rule of thumb is protozoa get removed above 1 micron, bacteria get removed above .1 micron, viruses get removed above .01 micron.   The smaller the pore size, the more clean the water will be, but it may be more susceptible to clogging. Make sure you read the 'absolute' pore size rather then the 'nominal' pore size.

Filter medium: The material used to manufacture the filter cartridge greatly affects the quality and cost of a purifier. Materials are:

Pump Force: This gives an idea of how hard it is to push the handle in and out. A smaller number means easier pumping. 16 is pretty high.

Strokes per Liter: Tells how many times you need to pump to get a liter of water. A smaller number means more water per pump.

Instructions: Make sure you can read and understand the instructions. A unit should be simple to use, clean, and repair or it will be a waste of money. If the grammar of the instructions is too poor to understand, I would pass on that product.

Cost: You can get a cheap unit for $20 or something extravagant for $700. There are great ones available for around $100 that do an excellent job of producing safe, clean, virus free water. I wouldn't chance a cheaper product and I'm too stingy to throw away more money than I need to. Also, take into account the cost of any required chemicals.

Servicability: Some purifiers have cleanable filter elements, others you just replace the canister. Most all portable purifiers have moving parts that can wear out or break. Make sure you have replacement parts and know how to disassemble and re-assemble your gear. If service is a convoluted process, look for a different product. Products that include a service kit are a plus in my mind.
A unit should be servicable in the field, not requiring special tools or environment.

More to Consider

Here are a few more things to think about both when purchasing and using your portable water purifier.

Read about   Water Purifier Products

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