How Much Bleach Per Gallon: The Number Changed and Most Charts Didn't

Figures last verified 11 September 2026

The familiar figure of 8 drops per gallon, which appears on nearly every emergency preparedness page, belongs to household bleach containing 5.25 to 6.0 percent sodium hypochlorite. Household bleach is now commonly 8.25%, which is stronger, and EPA's figure at that concentration is 6 drops per gallon. Using the old figure with new bleach overdoses the water.

Read the percentage on the bottle before you dose anything. That single step is the whole article, and the reason it needs saying is that the charts you will find frequently do not ask you to. Ready.gov, the federal preparedness site, still gives a single dose for bleach containing 5.25 to 6.0 percent sodium hypochlorite, on a page last updated in February 2021.

What changed

Older guidance is keyed to household bleach containing 5.25 to 6.0 percent sodium hypochlorite. EPA's current table has two columns, 6% and 8.25%. Some stores still stock the weaker formulation, but manufacturers have been moving away from producing it. Dilutions have to be adjusted to reach the same parts per million, and the error matters in both directions. Too much chlorine is corrosive and irritating to skin, eyes, and the respiratory tract. Too little fails to kill pathogens, which is the failure mode that gives no warning.

Brand lines complicate it further. Within a single manufacturer's range, the regular, ultra and concentrated products can carry different concentrations, less of the stronger one achieves the same disinfection, and all of them sit on the same shelf in near-identical bottles.

So the percentage is not predictable from the brand, the bottle size, or the word on the front. It is printed in the active ingredients line, usually in small type, and it is the only thing that determines the dose.

The dosing table

This is EPA's table exactly as EPA publishes it, with its volumes and its two columns. Stir, then let the water stand 30 minutes before drinking.

For a volume not in the table, work up from a row that is, rather than from a figure someone else scaled. EPA does not publish a row beyond eight gallons.

If the water is cloudy, let it settle and filter it through a clean cloth, paper towel, or coffee filter first, and double the amount of bleach if the water is cloudy, colored, or very cold. Organic material consumes chlorine, so a dose adequate for clear water can be entirely used up before it disinfects anything.

After 30 minutes the water should carry a faint chlorine smell. If it does not, treat again with the same dose and wait another 15 minutes. If it still carries no odor after the second treatment, discard it and find another source.

EPA's maximum residual disinfectant level for chlorine in drinking water — the highest level allowed — is 4.0 mg/L, and these doses target well below it.

Which bleach

Plain, unscented sodium hypochlorite only. Nothing else.

Scented bleach, splashless bleach, gel bleach, and anything with added surfactants or thickeners contains compounds not intended for ingestion. Splashless formulations in particular are thickened and are not suitable regardless of the hypochlorite percentage.

Non-chlorine or color-safe bleach uses hydrogen peroxide and does not disinfect water.

Pool shock is calcium hypochlorite rather than sodium hypochlorite and is dosed completely differently. It stores far longer than liquid bleach and is used by making a stock solution first, which is a different procedure and not interchangeable with the numbers above.

Bleach degrades, which changes the dose again

Liquid bleach loses potency in storage, faster in heat or light, which is why EPA tells you to use bleach stored at room temperature for less than one year. A three-year-old bottle in a hot garage may be substantially weaker than the label claims, which pushes in the opposite direction from the concentration increase and is impossible to correct for precisely.

Practical handling. Write the purchase date on the bottle in permanent marker. Rotate it annually rather than treating it as a long-term storage item. Keep it cool and dark. If bleach is the backbone of your water plan, calcium hypochlorite in granular form stores for years rather than months and is the better long-term holding.

What chlorine does and does not handle

Chlorine at these doses kills bacteria and inactivates viruses reliably. It handles Giardia with adequate contact time, which is why the 30 minutes wait matters rather than being a formality.

It does not reliably inactivate Cryptosporidium, which is chlorine-resistant and requires filtration, boiling, or ultraviolet treatment. It does nothing for chemical contamination, heavy metals, or dissolved solids, and treating chemically contaminated water with bleach produces chemically contaminated water with chlorine in it.

Which treatment method addresses which contaminant is worked through in filter, purify, or distill: what each one actually removes. Bleach is the tool for biological contamination in otherwise clean water, and it is the wrong tool for anything else.

Boiling remains the most reliable method available without equipment. A rolling boil for one minute, or three minutes above 5,000 feet, handles everything biological including Cryptosporidium.

Treating water for storage versus treating it before drinking

These are different jobs and the second one is usually unnecessary.

Municipal tap water arrives already chlorinated and does not need additional treatment before being stored in a clean, sealed, food-grade container. Adding bleach to already-treated water is a common practice and accomplishes little, since the residual chlorine is already present and will dissipate at its own rate regardless. Whether stored water degrades at all is covered in does stored water go bad.

Well water, spring water, and any untreated source should be treated before storage, using the table above.

Water of unknown provenance during an emergency should be treated at the point of use, immediately before drinking, rather than treated once and stored.

The practical procedure

Find the sodium hypochlorite percentage on the bottle. It is in the active ingredients line.

Pick the matching column above. The table covers every concentration sold for household use, so the only thing you need is the number on the label.

If the water is cloudy, let it settle and filter it through a clean cloth, paper towel, or coffee filter, and double the amount of bleach if the water is cloudy, colored, or very cold.

Stir thoroughly and let it stand 30 minutes.

Smell it. A faint chlorine odor means it worked. No odor means treat again.

The water sources already inside your house are cleaner than anything you will find outside and mostly need no treatment at all, which is covered in the water already in your house. How much of it you need is in where the one-gallon-per-person-per-day number comes from.