Grayl Internal Frame Backpacks

Filter vs. Purifier

• Filters: Remove protozoa (Cryptosporidium, Giardia) and bacteria (E. coli, Salmonella)—main concerns in the U.S. and Canada. 
• Purifiers: Also combat viruses such as hepatitis A, rotavirus and norovirus.  

Filter Types 

• Straw: Light, easy to use. Only works at water source. 
• Bottle: Lightweight, quick, affordable. Water volume limited by bottle size. 
• Gravity: Easy to use, handles large quantities of water, has a replaceable element.
• Pump: Precise, works in shallow water, has a replaceable filter. Bulky.
• Ultraviolet light: Fast, no filter to replace. Requires batteries and prefiltering for cloudy water. 
• Squeeze: Compact and affordable. Water quantity limited by reservoir size. 
• Chemical: Inexpensive, ultralight backup method. Long wait time, doesn't taste great.