That said, you can at least test the QuickDraw to see if it has been compromised.
However, if you're traveling in below-freezing temperatures during the day as well, you may want to look elsewhere for a filter that isn't as susceptible to the cold. The solution is to keep your filter in your sleeping bag with you at night (made easier by the two caps on the QuickDraw). Typically, this won't be an issue for most three-season backpacking. THE FREEZING: One of the major drawbacks to the Platypus QuickDraw, as with all hollow-fiber membrane filters, is the fact that it can freeze. The filter attached to a Smartwater bottle The Bad Alternatively, you can shake the filter while it's attached to a bottle to clean it out, but this doesn't work as well as backflushing. Simply take the clean side, press it up against a water bottle (with the cap removed) to create a seal, and squeeze your water bottle. The good news? You don't need any special tools or accessories to backflush your QuickDraw. The bad news? You have to backflush (if you want to keep your filter performing with a reasonable flow rate). THE BACKFLUSHING: Backflushing is the process by which you run water backward through the QuickDraw to remove all the gunk that has been caught inside while filtering. I completed the Arizona Trail alongside someone using a Sawyer Squeeze, and I found our flow rates to be about the same overall. After repeated use (and backflushing), you can expect considerably less. Platypus promises 3 liters per minute, but this number has to come from “ideal testing conditions” and with a new filter. THE FLOW RATE: The Platypus QuickDraw Microfilter has a decent flow rate out of the box. If you see bubbles, your filter is compromised and is no longer filtering your water. According to the instructions, you fill your reservoir with 1 liter of water, attach it to the filter, filter half, flip the reservoir upside down so the bottom of the filter is in contact with air inside the empty reservoir, squeeze firmly to push air through the filter, and then you look for a steady stream of bubbles. However, the QuickDraw is also the first hollow-fiber membrane filter (I've encountered) that can be field-tested to check whether it has been compromised. THE TESTING: Yes, the QuickDraw can be rendered ineffective if it freezes or is dropped. The one complication? If you're using a rigid container (like a Smartwater bottle), you'll have to let some air into your bottle while filtering (let it reinflate) to successfully (or at least without maximum frustration) empty the dirty water through the filter into your clean receptacle. You can squeeze the water into a clean reservoir or directly into your mouth. THE EASE OF USE: Using the Platypus QuickDraw Microfilter is simple – screw it onto your water reservoir and squeeze. I choose to sleep with the filter in my sleeping bag and the two caps never leaked during the night.
Since this is a hollow-fiber membrane filter, it is recommended that you keep it warm in near-freezing temperatures. The dirty side has a screw-on cap that fits tightly enough for me to not worry about water leaking out while the filter is stored. The clean end has a hinged cap that appears to be quite durable and shows no signs of breaking off (this was a concern of mine when I first got the QuickDraw). THE CAPS: The QuickDraw comes with a cap on both the clean and the dirty end of the filter.