Talk me through water filtration and purification

July 7, 2013 1:32 PM

As I'm spending more and more time on bike trips where there are many long stretches without access to reliable tap water, I'm starting to investigate water filters and purifiers as a supplement/backup solution in case the extra water I carry runs out or spills or whatever. But there are so many kinds, and some of them seem really sketchy, and I'm getting overwhelmed! Can you point me to a good, comprehensive resource on how to choose and use water purifiers and filters? Or can you talk me through a typical real-world use? Take for granted that I'll be using them within the US and am unlikely to be traveling in areas where the natural water supply is seriously contaminated.
posted by rhiannonstone to Sports, Hobbies, & Recreation (15 answers total)

Iodine tablets are cheap and lightweight. You just fill up a water bottle and add two tabs of iodine. Then wait half an hour, and put in a tab of ascorbic acid (comes in the same kit), which precipitates out the iodine so the water tastes better. Some people say the water tastes bad even after that last step but I've never been able to tell.

If you do pick a fancy gadget-based method, you probably want to carry iodine as a backup anyway in case it breaks or gets lost.
posted by miyabo at 1:53 PM on July 7, 2013 [1 favorite]

Best answer: I have been using one of these for almost 10 years of backpacking. I have seen and tested a few other purifiers, but I always come back to this one. High initial investment ($100), but has more then paid for itself.

On a bike you may want to look at something smaller. If your need is not to make fresh water but to have in-case you run out of your existing supply, then as a backup iodine tablets or chlorine based drops should suffice in a pinch.
posted by token-ring at 2:13 PM on July 7, 2013

Go talk to the good folks at your local REI - they can steer you to something that will work, and will be guaranteed.
posted by dbmcd at 3:46 PM on July 7, 2013

Seconding REI. In my experience, the sales people are really knowledgeable and never try to upsell you. If you ask an experienced kayaker, they'll go find a different salesperson who's into biking in remote areas. Possibly the one store I leave feeling really positive about.
posted by jeff-o-matic at 3:57 PM on July 7, 2013

Best answer: I use this filter by Sawyer, and it works great. They make an inline adapter, so if you're riding with a Camelbak, you can cut your hose, route the hose through this filter, and then you can just dump dirty water directly into your hydration bladder and drink clean water.

If you don't want to dump dirty water into your bladder, they make a different inline adapter so that you can use the filter to push clean water into your bladder. I've used that one, and it works fine, too.
posted by spikeleemajortomdickandharryconnickjrmints at 4:21 PM on July 7, 2013 [1 favorite]

This isn't your exact question, but the platypus system is far and away the easiest and fastest filter that I've used. It's fairly light and can clean a huge amount of water without you having to pump. You put dirty water in the dirty bag, hook the filter up, and let it drain into the clean bag. That's it. I wouldn't rely on portable filtration for any area with likely heavy metal / lead contamination, but those are usually cities where you could stop and get tap water. Iodine will kill bugs but do nothing for organic chemicals that I'd worry about next to a road.
posted by Ms Vegetable at 5:28 PM on July 7, 2013

Take for granted that I'll be using them within the US and am unlikely to be traveling in areas where the natural water supply is seriously contaminated.

Contaminated with what ? Giardia is common enough in many outdoor settings.
posted by k5.user at 8:50 AM on July 8, 2013

Response by poster: I meant so heavily contaminated that it's not potable even after treatment. Is giardia something that can be treated for?
posted by rhiannonstone at 1:21 PM on July 8, 2013

Best answer: Yes. Most good filters will get giardia. What's hard to get are viruses. UV systems like the Camelbak All Clear and the SteriPen will kill every living thing in the water (if the water is clear). There is a beefier version of the Sawyer filter I linked to that will tackle viruses, but it's better to use it in a gravity system, because the flow rate is about 25% of the regular filter, so sucking water through it a part of a hydration bladder system is a bit difficult.
posted by spikeleemajortomdickandharryconnickjrmints at 2:25 PM on July 8, 2013

Response by poster: So the Camelbak All Clear looks nicely portable, and you can get a prefilter accessory which presumably gets the water "clear" enough to be disinfected. Am I missing something, or does that sound like a great solution for getting small amounts of clean water from a random stream or pond etc? Are there water sources that this system wouldn't work with? Microorganisms I need to be concerned about that it won't kill/neutralize/whatever?
posted by rhiannonstone at 3:30 PM on July 8, 2013

Best answer: Nope. It will kill all living things. You can use it to fill your bike bottles so you can carry more clean water when you need to use it. It does not filter sediment, but that prefilter accessory works pretty well.
posted by spikeleemajortomdickandharryconnickjrmints at 5:50 PM on July 8, 2013

Response by poster: Are there non-living things I need to be concerned about? Or are those what get physically filtered out?
posted by rhiannonstone at 2:10 PM on July 11, 2013

Best answer: Heavy metals, arsenic, etc. UV won't do anything for that, but then, most porous filters won't, either. The SteriPen is relatively small, lightweight, and can purify water that you scoop up using your bike bottles.
posted by spikeleemajortomdickandharryconnickjrmints at 4:15 PM on July 11, 2013

Best answer: My understanding is that the steripen and such don't help with is turbid /scummy water (they don't change the taste) or silt. The prefilter on the All Clear should get out dead bugs and such.
posted by Ms Vegetable at 11:53 AM on July 13, 2013

Best answer: The only time I've ever had a serious problem was on a trip in the Southwest where the only available water was extremely sandy/silty, and we only had a Steripen and backup iodine. We had to let the water sit for several hours before being drinkable, and one of my trailmates got intensely ill after getting very thirsty and drinking the silty water prematurely. So yes you do have to worry about nonliving things sometimes. A filter would have been really nice in that situation.
posted by miyabo at 1:19 PM on July 13, 2013