Many of our filters use Hollow Fiber technology, these filters should not be allowed to freeze and can be damaged from a drop onto a hard surface or rock. Water expands when frozen, and this can burst the individual hollow fibers or rupture the cartridge itself. If you think your filter did freeze or sustain a drop; perform an integrity check which will tell you if it is still working properly. This process varies from filter to filter, but you can find the instructions for each filter in its owner’s manual, on the products web page, under the documents and FAQ tab.
Our instructional videos are hosted on YouTube, and you may be able to find them more quickly by searching directly there. Each brand has its own channel; Platypus MSR Gear use the channels’ search tool to find your product.
As a general rule, it’s best to prevent any filter from freezing by bringing it inside your tent at night—or even placing it in your sleeping bag—if temperatures are expected to drop below freezing.
Hollow fiber filters are also vulnerable to damage from impacts, such as being dropped on a hard surface. For this reason, we recommend memorizing the integrity test procedure for your filter, or carrying a hard copy or screenshot of the instructions on every trip. That way, if something questionable happens, you’ll be prepared and won’t be left wondering whether your filter is still safe to use.