Bleach can make water safe. The label decides if it will.

Quick answer: For clear water, add 8 drops of plain 6% household bleach per gallon (6 drops if it's 8.25%). Stir, then wait 30 minutes. It should smell faintly of chlorine. If it doesn't, dose it again and wait another 15 minutes. Boiling is still the first choice when you can do it.

That's the EPA's emergency method, and it works. What the one-line version leaves out is everything that makes it fail.

Read the bottle first

Walk to the laundry shelf and pick up your bleach. Find the ingredients. You want one active ingredient: sodium hypochlorite, at roughly 5 to 9 percent. That's it.

Put it back if it says any of these:

• Scented (lemon, fresh linen, anything)
• Color-safe
• Splashless or "thickened"
• Added cleaners or detergents

The EPA says to avoid all of them for drinking water. Those additives aren't something you want to swallow, and nobody has promised they leave the water safe. A bottle of "splash-less" bleach looks identical to the plain stuff on the shelf. It isn't the same product.

Then find the percentage. Regular bleach is typically about 6 percent. Concentrated versions run higher, often 8.25 percent. The number matters because the dose changes with it.

The dose

The EPA's table for clear water is simple at household scale:

| Water | 6% bleach | 8.25% bleach | |---|---|---| | 1 quart | 2 drops | 2 drops | | 1 gallon | 8 drops | 6 drops |

If you can't tell the strength, EPA guidance is 10 drops per gallon of clear water. For bigger containers, multiply. A 5-gallon jug at 6 percent takes 40 drops. Count them. Don't eyeball it, and don't pour a capful because the container looks big.

For larger volumes the EPA publishes a fuller table. Print it and tape it inside a cabinet door with the bleach, because you won't remember it at 2 a.m. with the lights out.

One honest caveat. "A drop" depends on the dropper. The table assumes a standard medicine dropper, and a cheap one or a wide-mouth squeeze bottle can put out a very different drop. Buy a dropper, label it bleach only, and keep it with the bottle.

The steps

1. Start with the clearest water you can find.
2. Add the bleach by the table.
3. Stir or shake so it mixes through.
4. Wait 30 minutes. Cold water needs longer, so give it more time.
5. Smell it. A slight chlorine odor means enough was added. No odor means the dose got used up, so repeat it and wait another 15 minutes.

The smell test is the step people skip, and it's the only feedback you get. Smell it.

Cloudy water is a different problem

Chlorine works on what it touches. Sediment and organic gunk soak it up and shield germs from it. If the water is cloudy, murky or colored, strain it through a clean cloth or a paper coffee filter, or let it settle and pour off the top. The EPA also says to double the dose for cloudy water.

Doubling doesn't rescue truly filthy water. If it's dark, smells of fuel or sits under a flooded field, find another source.

Where bleach won't help

Bleach treats germs. It doesn't remove chemicals, fuel, pesticides or heavy metals. Floodwater with any of that in it isn't a bleach job.

Chlorine is also weaker against some parasites, Cryptosporidium most of all, and cold or cloudy water makes it worse. That's why official guidance puts boiling first: a rolling boil for 1 minute, or 3 minutes above 6,500 feet. If you have fuel and a pot, boil. Use bleach when you don't, or to treat the water you stored.

And if your city or county issues a boil-water notice, follow what they tell you. They know what's in your system and you don't.

Mistakes worth avoiding

Old bleach. Bleach weakens with age and heat. A bottle that's baked in a garage for two summers is a guess, not a disinfectant. Buy a fresh jug about once a year and use the old one for the laundry. It costs a couple of dollars. Treat it like the batteries in your smoke detector.

Mixing the wrong things. Never combine bleach with ammonia, vinegar or other cleaners. It can release toxic gas. Don't pour it into a container that held anything else.

Dirty containers. Treated water in a filthy jug is just stored contamination. Use food-grade containers, wash them with soap and rinse well. Skip old milk jugs. The residue is stubborn and breeds bacteria.

Skipping the label on the water. Write the date on the container. Anybody in your house should be able to tell what's treated and what isn't, especially a kid or a houseguest.

Leaving the bleach where kids can reach it. It's corrosive. Keep it in the original bottle, capped, up high, away from food and medicine. The dropper goes with it.

How much to treat

The standard planning number from federal preparedness guidance is at least one gallon per person per day, for drinking and basic sanitation. A family of four over three days is twelve gallons. That's 96 drops of 6 percent bleach, plus a good while standing at the sink counting.

Don't wait for the emergency to find that out. Count out a gallon's worth once, on a quiet Saturday, with a pitcher and the dropper. Time the wait. Smell the result. After that you won't be learning it in the dark.

If you haven't built out the rest of the plan, start with The Seventy-Two Hour Kit Your Family Will Actually Use. If you're thinking past three days, What a Week Without Power Actually Takes covers the harder math. And if your folks live on their own, What Your Parents Need Before the Next Three-Day Outage is worth a phone call and a trip over with a bottle of plain bleach and a dropper.

Check the label tonight. It takes thirty seconds, and it's the one step that decides whether the other eight drops matter.