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Buying Guide - Water Treatment
 Why Treat Water?
Your health depends on it. Even stream water that looks fresh and clean
may contain bacteria, giardia, cryptosporidium and other nasty microbes that
could make you ill, or worse. Water treatment is especially important in the
wilderness or at sea, where professional medical care could be days away.
Pump/Gravity Filters.
All hand pump filters have the following characteristics in common:
(a) hand crank lever for pumping water, (b) a water intake hose that draws water from the water source (such
as a stream), (c) a replaceable filtration element or cartridge through which the
water is filtered, (d) a water hose or adapter that outputs filtered water into a water
bottle or reservoir.
Most pump filters work the same way:
- The hand crank lever is used to pump water through the intake
hose;
- The water is pulled from the intake hose through a replaceable
filtration element or cartridge;
- The filtered or purified water then outputs through a hose or
bottle adapter for collection into a reservoir or water bottle.
Gravity filters use a similar method, but rely on gravity instead of
a hand crank lever.
Pros: Most can filter water mixed with sediment or
mud. Can produce relatively large volumes of potable water in a
short period of time. Requires no batteries or external power
source. Most are quite durable.
Cons: Ultralight models are available, but they are
still generally heavier and bulkier than chemical tablets and UV
purifiers. Many do not eliminate small viruses (but this is
generally not a significant concern in North American streams and
lakes).
Notes: All filter cartridges or elements need to be
replaced (or cleaned) after some period of use. Ceramic elements
last the longest (with some lasting several years) and can be
cleaned repeatedly. Fiberglass or paper cartridges are efficient and
economical, but need to be replaced after a couple of hundred
gallons of filtration.
Chemical Tablets & Solutions.
Iodine or chlorine dioxide
can be added to suspect water to disinfect the water of biological
pathogens, such as bacteria and viruses.
Pros: Extremely lightweight and compact. Most kill
viruses, in addition to bacteria, cysts, giardia and
cryptosporidium. Good for emergencies and for use in your hydration
pack.
Cons: You must plan ahead, as it can take up to 4
hours to completely disinfect water. Requires a relatively clear
water source (such as a running stream), as chemicals obviously do
not get rid of sediment or mud.
Ultralight Violet Light
Purification. UV light purifiers use ultraviolet light to quickly and safely
destroy the DNA of microbes. Although relatively new to the outdoor
market, UV technology has been used by bottled-water plants and
hospitals for over 60 years.
Pros: Proven technology. Lighter weight and more
compact than hand pump filters. Destroys the DNA of virtually all
microbes.
Cons: Requires an external power source -- i.e.,
batteries. Requires a water source that is relatively free of
sediment and mud (unless a pre-filter is used). Process is
relatively quick, but yield-per-minute is still about one-half that
of a compact hand pump filter. More fragile than hand pump filters.
Desalinators.
Desalinators remove sodium from sea water, to make in drinkable by
humans. Desalinators are only necessary when filtering sea water.
Desalination is not necessary when filtering fresh water from streams or
lakes, which do not have a dangerously high sodium content.
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