If you happen to be carrying only untreated water for use with your LifeStraw and then come upon an emergency need for medical irrigation, what's wrong with dropping about a cc or more of liquid iodine into your untreated water? (borrow the iodine from the medical supplies you are carrying) The water would be safe enough for irrigation use in a few minutes.

Of course, who wouldn't prefer to have unlimited clean water available at all times? But I see no reason to limit yourself to only one method of water treatment. Carry iodine (itsy-bitsy small and lightweight). Carry MicroPur (itsy-bitsy small and lightweight). Carry a LifeStraw (a bit larger than the first two things, but much lighter than a conventional pump filtration device). Carry equipment for boiling water. Carry a pump filter too if that's what you prefer. But I think I would feel comfortable enough leaving that out for BOB use. Two chemicals, fire, and a LifeStraw sounds like a decent enough group to take care of my anticipated needs. For something that in all reality I will most likely never use, just keep it in my BOB, I figure the LifeStraw at $19 is a suitable enough replacement for a pump filter at $80+. I wouldn't knock someone who wanted to carry a pump filter though. We all make choices based on what we foresee as our potential needs.