To find the >best camping water filters you have to weigh how you will use the water filter and the type of water you want to filter. You don't want to lug around a large gravity fed water filter designed for a campsite if you are backpacking. You also don't want a small personal use water filter for a large crowd at a campsite you can drive to.
Let's start with what can be in the water you find in the backcountry. The most common organism found in water worldwide is Giardiasis ( Giardia ).
Giardia can cause diarrhea, headaches, loss of appetite and fevers. The fever part is referred to by outdoorsman as " Beaver Fever ". Giardia comes from the small intestines of infected animals and humans. It is prevalent in ponds inhabited by beavers and muskrats. Giardia is spread in the cyst stage which is 6 - 10 microns in size. The mature stage is 10 - 20 microns.
I could write several pages on the parasites, bacteria and protozoa present in water. To see a better list check out Wikipedia/waterbornediseases.
Now that I scared you with unseen dangers it's time to look at filters that can remove these and make your water safe to drink.
There are three different use scenarios to consider when you want to purchase a water filter. Not many people need one for camping in campgrounds but there are filters that use gravity to force the water through the filter. The Katadyn Base Water Filter is ideal for purifying water for a larger group at a base camp. It is the best in it's class. There are heavier and more durable filters available but are 3 to 5 times more expensive.This filter can be used for backpacking and hiking but weighs a few ounces more than typical pump filters and care must be taken to protect the filter element from crushing.
Catadyn Base Camp Filter is a gravity fed water filter. It is capable of filtering 10 liters ( 2.6 gallons ) of water from its reservoir in about 20 minutes and filters the water through a pleated, activated carbon core filter element. The pleats give the element more surface area to allow more water to filter through. The activated carbon core removes unpleasant tastes.The filter element will filter about 200 gallons before it should be cleaned or replaced due to clogging. The filter and repacement elements come with a sponge to clean an element when the water flow is reduced. You can also prolong the life of the element by pre filtering the water through a coffee filter or an available prefilter to remove larger material. The element will remove particles to .3 microns which is smaller than any water borne bacterias. There is a valve on the outlet tube so you do not waste any filtered water while you swap containers catching the filtered water.
To use just fill the reservoir with water from a stream, river, or pond. Roll the top of the reservoir down to the hanging strap and connect the two buckles of the strap. Hang the full filter on a tree branch or tripod. Place the water tube into a clean container and turn on the valve. That is it. You will have plenty of safe filtered water in no time without pumping.
The MSR Mini Works water filter is a lever action pump water filter weighing 1 pound. The pump valve has a pressure release to protect the pump from over pressurizing. The lever offers a 4 to 1 pressure amplification to the piston to increase water flow. This amplification allows the water to be processed up to 1 liter per minute.
The filter element is a ceramic element with an activated carbon core. The ceramic element is designed to filter out particles and parasites as small as .2 microns.
The element is easily cleaned by unscrewing the body from the pump and removing the element. Clean the element with the supplied scouring pad. After you scour the element use the supplied diameter measuring gauge to check the thickness of the ceramic in the element. If the gauge slips around the element, the element should be replaced. If you are cleaning the element in the field, care should be taken to keep contaminated water out of the center of the filter.
The body is made of rugged high impact plastic and screws together. The pump and body can be taken apart for cleaning and repairs without tools. The base of the body comes with a screw in cover to keep the outlet sanitary and a water bottle can be attached to the threads. This makes it easier to control light weight bottles when filling.
The 4 foot long intake hose is flexible and comes with an adjustable float to keep the spring laden end out of the mud and sediment.
I used this pump extensively in Alaska, New Hampshir, Vermont and Maine. I accidently sucked up a small twig which jammed in the pump valve. The twig was easily removed by disassembling the valve. Besides normal element cleaning this was the only time I had to take the pump apart. I have recommended this pump to my friends and acquaintances.
To use the SteriPEN simply turn it on by pushing the button and immersing the light end into the water you want to purify. The light will emit visible blue and ultraviolet light. Stir the water to allow all the parasites to be accessed by the UV light. The blue light is just an indicator to tell you the unit is working. Once the water is purified SteriPEN automatically turns off. It takes about 48 seconds to purify 16 ounces of water and about 90 seconds for 32 ounces. If the water is cloudy or murky, purification will take longer.
SteriPEN uses two non chargeable lithium batteries and last for approximately 100 treatments of 16 ounces. Rechargeable batteries are available but only lasts for about 40 to 50 treatments. The rechargeable batteries can be charged with a computer USB connection or by a wall voltage adapter.
The lights are housed in a protective sleeve so the unit will work in very cold water without damaging the bulbs. The unit is also covered with a rubber coating to protect the circuitry and make it easier to hold when wet.
SteriPEN weighs just 3.6 ounces with batteries and comes with a neoprene case with belt loops. There is also an optional solar powered carrying case for on the go charging available.
I for one am not the kind to rely on electrical or electronic products but a friend of mine has one and swears by it.