I've used the steri-pen for several years on multiple trips into the mountains. It has always worked for me.


Things to consider with the steri-pen.

Get a bottle with a wide enough mouth.

Carry an extra set of batteries

Some sort of pre-filter is a good idea. I found one that screws onto nalgene bottles, but even one of those small, metal coffee filters would take particulate matter out.

The way it works is it scrambles the genetic material of the bad "bugs" with UV light. This prevents them from being able to reproduce. But, chemicals are not removed.

If you use a hydration bladder (like camelbak) you will have to obtain, treat, then transfer the water into the bladder.

The LED model doubles as a last ditch flashlight. (Which I've used on several occasions)

In my experience, they are effective, light and durable.