- I've seen them fail on other hikers as often as I've seen them work.
- Must use lithium batteries, which are hard to find in small resupply towns. If alkaline batteries are used, you can usually expect to only treat 2-8 quarts, whereas Lithium may last up to 100 quarts.
- Not as effective if water is cloudy or discolored.
- Can leave the threads of the cap untreated.
- They are heavier than my bleach and Sawyer inline filter method.
- They are more expensive. Particularly when you include battery costs.