How Many Drops of Bleach to Purify a Gallon of Water?
Ready.gov's official emergency disinfection ratio is 1/8 teaspoon — about 8 drops — of plain, unscented liquid chlorine bleach per gallon of clear water, stirred and left to stand 30 minutes; if it doesn't smell faintly of chlorine afterward, repeat the dose and wait 15 more minutes.
The one thing to know: Ready.gov's official emergency disinfection method: 1/8 teaspoon (about 8 drops) of plain, unscented liquid household chlorine bleach per gallon of water, stirred and left to stand 30 minutes. If it doesn't smell faintly of chlorine afterward, repeat the dose and wait 15 more minutes. Scented, color-safe, or splash-less bleach formulas are not the same product and shouldn't be used for this.
The exact method, step by step
- Start with clear water. If it's cloudy, filter it through a clean cloth or coffee filter, or let it settle and draw off the clear layer first.
- Add 1/8 teaspoon (about 8 drops) of plain, unscented liquid chlorine bleach per gallon.
- Stir, and let it stand for 30 minutes.
- Smell it. A faint chlorine odor means the dose worked.
- No chlorine smell? Repeat the dose and wait 15 more minutes.
The method comes from ready.gov's Water page, which is also the source of the storage baseline (one gallon per person per day) this site's water storage guide is built on.
What bleach disinfection can't do
- It doesn't fix chemical contamination. Bleach targets microorganisms; fuel, pesticide, or industrial contamination is a different problem, and disinfecting doesn't address it.
- It's not for scented or splash-less formulas. Those contain additives; the method assumes plain, unscented liquid chlorine bleach only.
- Bleach itself ages. Liquid chlorine bleach loses strength over time in storage — note the production date on the bottle you keep with your kit and rotate it like any other consumable at your kit check.
Gear that covers the same job
Research-based picks (how we evaluate) — live Amazon search links, no prices or ratings, an honest drawback on each.
Water Preserver Water Preserver Concentrate
Liquid stabilizer, treats up to 55 gallons, extends storage to 5 years per label
A pre-measured alternative to counting bleach drops, letting stored water go years between rotations instead of 6 months.
Best for: Buyers who want to store water once and not think about rotation constantly
Watch out: This is a storage stabilizer, not a substitute for boiling or a certified filter if the water source itself is questionable — read the label's exact dosing.
Check price on AmazonSawyer Sawyer Squeeze Water Filter
0.1 micron hollow-fiber filter, removes 99.99999% bacteria/protozoa, no batteries
A compact, no-power filter that works on questionable found water (streams, rain barrels) when your stored supply runs out.
Best for: Extending water security beyond your stored supply without electricity
Watch out: Filters remove bacteria/protozoa but not viruses or chemical contaminants — pair with boiling or purification tablets if the water source is suspect for those.
Check price on AmazonFrequently Asked Questions
Ready.gov's emergency disinfection method is 1/8 teaspoon — about 8 drops — of plain, unscented liquid household chlorine bleach per gallon of clear water, stirred and left to stand for 30 minutes.
Repeat the dose (another 1/8 teaspoon per gallon) and let it stand 15 more minutes. A faint chlorine smell is the sign the dose was sufficient.
No. Scented, color-safe, and splash-less formulas contain additives and are not the same product as plain liquid chlorine bleach — ready.gov's method applies only to plain, unscented bleach.
The 8-drops method is for water that is clear and free of visible contamination. Cloudy or visibly dirty water should be filtered or allowed to settle first, and bleach does not remove chemical contaminants.
For stored water, a pre-measured stabilizer product avoids drop-counting and extends rotation intervals; for found water, a 0.1-micron hollow-fiber filter handles bacteria and protozoa without power, though it doesn't remove viruses or chemicals.