Very good point, Erik. Most water sources in North America usually just need to be sanitized to drink. (I'm talking wilderness sources, not the ditch in the back yard!) In most cases, purification is way overkill. Most folks confuse the terms "purify", "disinfected", "fit to drink", and so forth. I'm a part time environmental engineer (well, mostly retired), and can wax poetic on the differences. I can also be very boring!
@Hikes_in_RainIn your opinion, is the fact that I can't filter out viruses with my Sawyer Squeeze really an issue in the US lower 48? I've never had an issue using the squeeze and mini, but maybe I've just been lucky. I'm asking because while I feel the risk is pretty low, I really don't want to find out the hard way either. My thought is that I'm mostly filtering for dirt and bacteria.
No sir, SILHiker, in my best professional opinion, viruses aren't really an issue on the North American continent (not just the lower 48). Simple disinfection (and dirt removal), via filtration or chemical disinfection (doesn't remove dirt), is pretty much all you need. In fact, I no longer treat water I use for cooking, since I'm going to boil it anyway. Again, just to clarify, I'm talking wilderness sources. Springs, for example. The only thing that keeps me treating fresh spring water bubbling right out of the rock is paranoia. (A degree in medical technology and two in engineering will do that to you!) A stream you can look upstream and pretty much see the source, pretty close to being good to drink from. My only concern there would be critters using it as well. So, just disinfect.
See, told you I could be boring!
For water filtration, which should be fine enough for an R2R hike of the Grand Canyon, I would also suggest the Sawyer squeeze paired with a 2 liter Cnoc vecto for dirty water and a couple of 1 liter smart water bottles for clean water. For extra protection I back my squeeze with up with a Sawyer mini which does not have as good of a flow rate as the squeeze but works well for a backup in case of a gear failure with the squeeze.
I'd also recommend swapping the cap on the squeeze for a smartwater sports cap so you can backflush on the trail without carrying the plunger. Also, remember to bring some extra smartwater bottle caps in case one is accidently lost in a stream during a refill. Have fun!
I use the Sawyer Mini, though the larger Sawyer might be preferable for a group (it will go faster). I bought a pair of the 64oz sqeeze bags for carrying & filtering water. I cut the top off the smaller one that came with the filter, which I use for scooping water from the stream or lake. Doing it that way is much easier than trying to fill an uncapped bag by submersing it.
Regardless of which filter system you use (I've used both my Katadyn and my hiking buddy's Sawyer for years), when in Grand Canyon if you'll be drawing water directly out of the Colorado River or in more remote areas where only pothole water or streams with limited flow is available, you should take along a plastic zip bag with several common drip coffee filters and a couple of wide rubber bands to put around the system filter before placing it into the water source. It will weigh practically nothing, but will provide a needed extra screen to prevent the really fine (small-diameter) solid particles from clogging your system's filter. With the Sawyer, I advise having a trashwater plastic zip bag that can be used to first pour the water through the coffee filter into its intake trashwater bag is effective and the rubber band can be used to clamp it around the intake (so it forms a deep cone inside that intake spout). If you're using a Katadyn, the scratch bag can be the source drawn from after scooping water out of any cruddy pothole or low-flow stream raw water sources.
I have been using the Katydyn Hiker for a long tine and have always been satisfied, but when backpacking alone have switched over to the Sawyer Mini to save weight and space. I also carry a few Micropur Tablets in case I lose my filter, it breaks, or for what ever reason need a back up, but I have never had to use them.