Not paying another $40 for a MSR Hyperflow Cartdridge

One problem with Sawyer is you can't let it freeze. It won't filter effectively but you maybe not be able to tell whether it's working. I assume MSR cartridge tolerates freezing As long as you have Sawyer, just ditch the entire MSR. Just screw Sawyer onto a re-used soda bottle.

The Hyperflow is a hollow fiber filter, as is the Sawyer. Neither one can be frozen with water in them. The issue with all filters is that the freezing water breaks the filter medium, causing cracks big enough to allow bacteria through. If it were possible to push all water from the filter it would be more freeze-tolerant. Some ceramic filters have in the instructions to store the filter cartridge in the freezer after drying it, if putting the filter into long term storage. Glass or hollow fiber filters, I run bleach water through prior to storage, otherwise bacteria growth clogs the filter permanently while stored.

Sounds like you are just using the Hyperflow for a pump. Good idea if it works reliably for you. Other filters can be tried with the 'pump,' as noted in the following thread: http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=99643

Yep…just like that. The Hyperflow is nice and compact also, everything still fits in the original pouch (Sawyer included). I will be taking it out for 5 days this weekend for a real test but have little reason to think it will have any issues….just $20 cheaper then the original.

I wonder if a Sawyer could tolerate some dilute vodka or Everclear as an antifreeze. You see the same issues in TV's stored for the winter.