[oldwild]

Hi. Just wondering. They often list purifying drinking water during weather emergencies with something like 4 drops of bleach per quart of water. Has anyone done this while backpacking? I normally carry a filter pump and iodine tablets as a backup, but this might be an option. Has anyone used this method?

[Damian]

I used to do this back in the day. Never had a problem. I even wrote to Clorox who responded in writing, validating the safety and effectiveness of this process. Very cheap and a jug will last a lifetime. Best if mild notes of bleach agree with you.

[Geography Nerd]

Many municipal drinking water utilities add sodium hypochlorite (bleach) into the water supply to disinfect the water. Depending on how close you are to a well/pump station you may notice a slight bleach smell (I do sometimes). They will often add extra bleach after construction or when putting new infrastructure into service.

[zimmertr]

You might find this post on /r/ultralight from yesterday interesting. It is a discussion about this video by Gear Skeptic discussing water treatment via filtration. This is the third video in a series. The second one discusses chemical treatment. Which is a bit more relevant to your topic. My takeaway is that if your water source is large and obviously not contaminated (think large lake) then chemical treatment will be more than enough in our area of the world.

[Malachai Constant]

The pills sold instant aqua etc are sodium chlorite or chlorine 2 for hot tubs and pools for about $10 for 2 lbs. Psychos think it's good for you but a teaspoon is enough for a 100 gal tub be careful.

[Randito]

The WA department of health offers this guidance. 5 drops per liter + 1 hour at room temperature. https://www.doh.wa.gov/Emergencies/BePreparedBeSafe/SevereWeatherandNaturalDisasters/WaterPurification Note that chlorine is ineffective against Cryptosporidium. Boiling is the low-tech solution to killing Cryptosporidium.

[Chief Joseph]

Cats like the smell of bleach so it must be ok.

[Bosterson]

Why not just splurge on a Steripen? I have the USB rechargeable one and it's good for 1-2 people for probably 3-4 days as long as you only use it on drinking water vs cooking water. (I've met people who filter their cooking water... Which they then boil. What?) If you take a power bank or backpack with a solar panel, as people do these days, you could probably keep it topped off indefinitely. Bonus points for no extra flavor in your water.

[jinx'sboy]

Back in the day……we used bleach, sparingly, to deal with a “bad” test when we sent in water samples from a FS campground water system. These systems typically involved underground cisterns, loooong runs of small diameter - sometimes ancient iron/plastic - pipe. And wells and/or pipes running from a spring. Bleach…in some quantity. Let it sit, run the faucet or spigot for a while. Let it sit again for a bit…then let the water run again. Repeat as needed. Test again. OK? cool. If not OK - do it all again. And test again. Seldom failed. I recall that was a monthly test, by County requirement.

[InFlight]

I normally use a filter, currently BeFree. I have used the Sawyers, and still own the MSR Cartridge. I have a MSR Trailshot in my day-hiking bag. I've also tried my son's Grayl, which is suppose to filter viruses as well. Weighs 11 ounces. However I always carry eight Chlorine Dioxide tablets as a backup. They weigh next to nothing (0.2 ounces). Chlorine Dioxide with a minimum 1 hour (longer with cold water) will kill all. The issue with pure Chlorine (or Iodine) is it not very effective for any Protozoa (Giardia or Cryptosporidium) The other advantage of carrying some chemical, is you can double treat (filter & chemical) some questionable water sources. I own a Steripen, but I seldom bring it along. If I was going someplace with known bad water it would be a nice non-chemical secondary treatment. I simply decided depending on a battery powered device (even with a spare battery) as a primary water treatment wasn't my preferred option.

[Navy salad]

[InFlight]

Filter and chemical water treatment is rated on a Logarithmic Reduction Value scale 1=90% 2=99% 3=99.9% 4=99.99% 5=99.999% 6=99.9999% 7=99.99999% Most Filters are Log 7or 6 for the Larger Bacteria. For protozoa, (Giardia, Cyptosporidium) most have a log 6 or 5 reduction. Water filters are not effective against any virus. "Effective" against Cyptosporidium is thus a Log 5 reduction. The published data suggests Chlorine Dioxide is around Log 3 reduction for Cyptosporidium, thus moderate compared to log 5. I'm wasn't advocating Chlorine Dioxide as a primary treatment. However, water filters can clog or freeze. At a 0.2 ounces for a backup option to adequately treat eight water bottles, it's a cheap and light insurance in the back-country.

[jimmymac]

I used to screen my water or melted snow through tighly woven fabric, into a bottle. Then, I'd treat that bottle with a chlorine dioxide tablet. I still use the screening disc for removing visible debris from the collected water, but I now squeeze the "raw" water out of the collection bottle, through an inline filter. (Pre-screening makes the filter perform better, longer.) I still carry a few chlorine dioxide tabs, since they weigh nothing and can't roll down a snowfield. But quitting the tablet disinfection keeps my gut's beneficial bacteria from being hit with the chlorine residual.