I found MSR chlorine tabs and a Sawyer microfilter in Wally world, which brought them into my price range. Plenty of water here in SE Florida, but the range of bacterial contaminants is terrifying. That prompted a review of my information on using sodium hypochlorite/clorox for water purification, and renewed a longstanding irritation about the cavalier use of "drops" as a unit of volume. Drops ain't uniform: iv administration sets can deliver 60 drops per milliliter or 15 drops per milliliter. Depends on the diameter of the drop orifice, viscosity of the liquid, and probably some other stuff of which I am ignorant. I did find a CDC reference that offers both drop notation and metric equivalence: 8 drops/ 0.75 ml per quart for clear water, 16 drops/ 1.5cc for cloudy.

This gratifies the physical chemist deep inside, tho the organic chemist aspect of my personality suggests that drop measurement is close enough.

Edit: Consensus also seems to be that regular vs concentrated clorox are not different enough to warrant a change in volume used. Metric syringes are widely available through pharmacies, craft stores, and American Science and Surplus website (sciplus.com, no affiliation).

This is just one reason why I prefer boiling as the most nearly fool proof means of purification.

True enough... It's just that boiling takes a fair bit of time and fuel. It also makes water taste flat and otherwise unpalatable IMHO at least until cooled down, which generally takes too darn long. OK in a cold climate but less so in summer.

This is why I often find chlorine tabs more convenient. Even filters are a good option on the move. Boiling is a reliable old-school method but only workable IME at a campsite or overnight shelter when you have plenty of time to spend at a fixed location.

Let me assure you, as an old desert rat that when you are really, really thirsty, "flat tasting water" will be the least of your concerns. Even under normal circumstances, I have never understood the problem, but my wife asserts that my taste buds were shot off in the war....

Purifying water from a typical babbling brook, I set up my canister stove, boil a pot, decant it into a canteen which is immersed back in the babbling brook, while pot #2 comes to a boil. My boil times approach those achievable with a micro wave (within a minute or so). Besides, the cup of hot water is readily transformed into a nice cup of tea, the elixir of the gods.

Maybe it's a desert rat thing then. During my time in North Africa I could never really get used to drinking hot beverages in scorching heat. I love the good old Arab tea with plenty of sugar and hopefully a bit of fresh mint, but it's just not the best thing to ward off dehydration.

I learned pretty quickly that nothing beats plain water for thirst, the cooler the better. The locals were of the same mind, even though they loved an occasional can of Coke (and possibly a secret sip of something high-proof when noone was watching) to lighten their day. I can't recall ever seeing anyone boiling water just to disinfect it. Fuel was in very short supply anyway so it wouldn't be practical.

We would drink whatever water was available, even from pretty awful looking wells full of trash, camel poo and stuff probably far worse than that. I always used chlorine tabs when the source was suspect. The Bedouin all drank straight from the well, I guess they were used to the local fauna. I never once got sick from drinking bad water, though I did get the inevitable diarrhoea from eating inadequately cooked food.

Anyway, it's horses for courses and boiling sure works fine in many situations. Honestly speaking though, it's rarely the most convenient option. It requires either building a fire or carrying a portable stove and fuel. Then it's a matter of bringing the water to the boil, which in my experience never quite beats the microwave, but I digress. Then it's cleaning the soot off the pot, packing everything back together and you still end up with a canteen full of flat warm water that tastes just terrible when your body core is overheating already.

So all in all, it would appear to me that disinfecting suspect water with a tiny chlorine tab is a whole lot less work to achieve pretty much the same thing. Even a good filter would work as a convenient alternative.

Boiling IMHE is only really practical in the long term when staying put at a fixed location with plenty of fuel available ... or if the water is so bad that chlorine tabs and filters can't handle the task. Which fortunately is rarely going to be the case in places we're likely to frequent, unless one attempts to drink water from a cesspit or some place with heavy chemical contamination. Not that boiling is going to help with the latter anyway.

But again, YMMV. This is no desert rat speaking, just a simple backwoods boy who prefers his water cold.

Here is a detailed and extensive discussion of the merits and negatives of various water treatment techniques: https://en.wikipedia.org/wiki/Portable_water_purification

Lots of options out there and none are clearly superior in all circumstances. I note that chlorine will require at least thirty minutes or more in order to become fully effective and is not necessarily fully effective against Clostridium (sp?) or Guardia.

When it comes right down to it, I will drink unfiltered water so that I can get back to town. Once there, I can seek cures for whatever ailment I might have acquired. I did this routinely some years ago, usually from springs and seeps in unpopulated areas. I have never suffered any bad consequences from this practice, although now I am considerably more cautious than I was in the past.....

Clostridium is a genus of soil bacteria including c. tetani (tetanus), c. dificil (opportunistic diarrhea in immune compromised patients), and c. botulina- not a common water contaminant problem. Giardia and cryptosporidia are the usual culprits- not bacteria, these are protozoa-critters-that are colon paarsites. Both are tough to kill, and both cause a relatively mild and usually self-limiting illness in folks with healthy immune systems. These are the bugs that will give you loose stools a week after exposure, and ones that you can seek cures for later on. Lots of folks who spend time in the woods are colonized with either or both of these, and have no symptoms.

Removing chemical contaminants, like pcb's is a little harder than inactivating the biologics.

Note to ponder: filtration removes the biological contaminants from the water: boiling and chlorine do not remove them, just kills them and leaves their tiny cadavers floating in your nalgene bottle-soup, of a sort.

I believe that Giardia often gets blamed for diarrhea in backcountry travelers when simple oral-fecal contamination is probably the far more common cause. Good sanitary, hand washing, disinfection and field kitchen practices will prevent this.

On a related note, there is a commercial hand sanitizer called "Qore 24" that we've evaluated as vastly more effective than alcohol based hand sanitizers. http://www.qore24.com/

When backpacking, I generally use a four liter Platypus bag to collect untreated water. I typically let it hang overnight, bleed off a bit from the bottom to remove any collected sediments, and gravity feed the water through an inline filter into a 3L Camelback and a 1L Nalgene bottle. If I'm being extra careful, I'll add some iodine and let that work overnight as well.

Aquamira's inline filters that promise Viral as well as bacterial removal, in their "Red Line" series, looks interesting, and I'll probably buy one next.

That's a very useful cite. Thanks!

I have replaced calcium hypochlorite with sodium dichloroisocianurate (NaDCC) pool shock as my long term storage chlorinating agent to work in conjunction with my Sawyer .1 micron 5 gallon filter system... this is for emergency water only...to titrate to a couple parts per million in a 5 gal source, requires only small dosages...if you are a metallic cartridge re loader, your powder scale can be used to measure out dosages... one grain (7000 grains per pound) is 65mg...depending on your concentration of NaDCC a grain or grain and half will give you about 3ppm (3mg/liter)... check with a pool test strip... once you have determined your necessary mass amount a simple dipper of a .22lr rifle case can be shortened to provide a volume measure...for my shallow well a 1/2 case full of 62 percent gave me a 3ppm reading... you need to do your own test however...

I think pool shock is more stable for long term storage than bleach, too.

Having had giardiasis, I can tell you, it is not a mild infection in the least. I also suffered from the treatment as the antibiotic (flagyl)I was given also wiped out all the probiotics in my system. In a survival situation, giardia and crypto are a big problem.

Chlorine effectiveness diminishes over time, as the chlorine compounds break down and become inert. Also, adding a little lemon juice or vinegar makes the chlorine used more effective as lowering the pH will make many of the microbes more susceptible. Warm water will also increase the effectiveness of the chlorine application.

I prefer to boil suspect water whenever practical, use filtration in most wilderness settings when boiling is not a viable consideration, and rely on chemical treatment only when such treatment is necessarily expedient. While biologics are a problem easily dealt with using these methods, chemical contamination presents some serious challenges. I have a couple friends who've dealt with arsenic poisoning from drinking untreated water.

Distillation would be the most preferable process for cleaning up water, but it too is not entirely foolproof.