For clear water the EPA says to add 8 drops of regular 6% household bleach to each gallon, or 6 drops if your bleach is 8.25%. Stir, then wait 30 minutes. Double the drops if the water is cloudy, colored or very cold. Worked out as a ratio, that is about 1 part bleach to 7,600 parts water, but measure in drops, not in ratios.
Boiling is the first choice, and CDC calls it the best way to kill germs in water. Bleach is for when you cannot boil. This page is reference material, not medical advice. If someone is ill after drinking water you were unsure about, call a doctor or the emergency number (911 in the US, 112 in Europe). The numbers below come from the EPA and CDC pages we checked on 25 October 2026.
The EPA table, copied as published
The EPA's emergency disinfection page (last updated 24 February 2026) gives this table.
| Volume of Water | Amount of 6% Bleach to Add* | Amount of 8.25% Bleach to Add* |
|---|---|---|
| 1 quart/liter | 2 drops | 2 drops |
| 1 gallon | 8 drops | 6 drops |
| 2 gallons | 16 drops (1/4 tsp) | 12 drops (1/8 teaspoon) |
| 4 gallons | 1/3 teaspoon | 1/4 teaspoon |
| 8 gallons | 2/3 teaspoon | 1/2 teaspoon |
*Bleach may contain 6 or 8.25% sodium hypochlorite.
Read the percentage on your bottle and use the column that matches. If you have 4 liters to treat, use the 1 gallon row, since a gallon is 3.785 liters.
The teaspoon figures are rounded. The table pairs 16 drops with 1/4 teaspoon but 12 drops with 1/8 teaspoon, which means the spoon amounts cannot both be exact. Count drops when you can.
The steps, in the EPA's order
- If the water is cloudy, let it settle, then filter it through a clean cloth, paper towel or coffee filter.
- Find a clean dropper from your medicine cabinet or emergency supply kit.
- Add the amount from the table, and double it if the water is cloudy, colored or very cold.
- Stir and let the water stand for 30 minutes. It should have a slight chlorine odor. If it doesn't, repeat the dose and wait another 15 minutes.
- If the chlorine taste is too strong, pour the water from one clean container to another and leave it for a few hours.
What that is as a ratio
Most people who search for a ratio want one figure to remember. The agencies do not publish one. They publish drops, so we worked it out.
CDC pairs 8 drops with half a milliliter for a gallon. A US gallon is 3.785 liters, about 3,785 mL. Dividing 3,785 by 0.5 gives roughly 7,571, so about 1 part bleach to 7,600 parts water. CDC's 5-gallon row (2½ mL) gives the same answer. For the weaker 1% bleach, CDC gives 2½ mL per gallon, which works out to about 1 part to 1,500.
Treat both as approximate. CDC lists 2 drops as 0.1 mL but 8 drops as ½ mL, so its own figures are rounded. Do not mix by ratio from memory: count the drops.
What CDC says, and where it differs
CDC's page has two bleach tables. The first covers bleach from 5% to 9% sodium hypochlorite, and CDC says that in the United States it will typically fall in that range. The second covers 1% bleach.
| Water | Bleach, 5% to 9% | Bleach, 1% |
|---|---|---|
| 1 quart or liter | 2 drops (0.1 mL) | 10 drops (½ mL) |
| 1 gallon | 8 drops (½ mL) | 40 drops (2½ mL) |
| 5 gallons | 40 drops (2½ mL) | 200 drops (12½ mL) |
The 1% table is exactly five times the other: 10 divided by 2 is 5, and 40 divided by 8 is 5. CDC also says to follow the instructions on the bleach label first and to use the tables if the label has none.
The two agencies agree where it matters most. Both give 8 drops per gallon for 6% bleach, both say to wait 30 minutes, and both say to double the dose for cloudy water. They differ in three small ways:
| EPA | CDC | |
|---|---|---|
| Bleach strengths | 6% and 8.25% | One dose for the range of 5% to 9% |
| Drops per gallon at 8.25% | 6 | 8 |
| Boiling, higher altitude | 3 minutes above 5,000 feet | 3 minutes above 6,500 feet |
If your bleach is 8.25%, the two pages are 2 drops apart for a gallon. Follow the label on your bottle if it has directions, and otherwise pick one agency and stay with it. On boiling, if you are above 5,000 feet, boil for 3 minutes and you satisfy both.
Which bleach to use, and which to leave on the shelf
The EPA wants regular, unscented chlorine bleach that is suitable for disinfection and sanitization as the label indicates. The label may say the active ingredient contains 6 or 8.25% of sodium hypochlorite. Do not use scented or color-safe bleach, or bleach with added cleaners.
The bottle also needs to be fresh. The EPA says to find fresh liquid chlorine bleach, or liquid bleach that has been stored at room temperature for less than one year. If the bottle in your cupboard is older, buy another.
The tables are written for products sold in the United States. If your label shows a percentage outside the ranges above, the drops will not match, so ask your local water or health authority before you guess.
Cloudy, cold or colored water
The EPA warns that disinfection does not work as well in cloudy or colored water. Let the water settle and filter it first, then double the dose. The same doubling applies to very cold water. That is why the 30-minute wait comes with a check: the water should smell faintly of chlorine afterwards, and if it doesn't, you repeat the dose and wait 15 minutes more.
What bleach does not fix
Bleach kills germs, but it does not clean water of everything else, and three gaps matter.
- Salt, heavy metals and most other chemicals stay in the water. The EPA says boiling or disinfection will not destroy these contaminants. That includes seawater, where bleach does nothing about the salt.
- Water with fuel, toxic chemicals or radioactive material cannot be made safe this way. CDC says so plainly. Use bottled water or another source.
- Some parasites survive better than germs do. CDC says disinfectants do not work as well as boiling against Cryptosporidium and Giardia. Chlorine dioxide tablets will kill Cryptosporidium as long as you follow the instructions correctly.
What our offline AI test said about bleach
We ran two small AI models on a laptop with no internet, on an Apple M2 Mac with 8 GB, on 22 October 2026. They were Llama (3.2, 3B) and Gemma (3, 4B). Each question came with a short passage we wrote from the EPA page, and the model had to answer from it. The bleach passage said: add 8 drops (about 1/8 teaspoon) per gallon (about 4 litres) of clear water, stir and wait 30 minutes, and double the dose if the water is cloudy.
Asked in Dutch how many drops go in 4 liters of water, Llama answered 2 drops. The passage it had been given says 8. Gemma answered 8 drops and a 30-minute wait, which was right.
In French the roles reversed. Asked how long to wait after adding bleach, Llama replied that the library had no specific information on bleach, even though the bleach passage was the first one it was given. Gemma answered 30 minutes, 8 drops per gallon, and double the dose for cloudy water. Separately, Gemma suggested treating seawater with bleach, which is dangerous.
We do not know why Llama said 2. The EPA's figure for a quart or liter is 2 drops, so it may have mixed up two rows, but the model never saw the EPA table, only our passage. We also did not test a model answering from memory, and the test was small: 24 passages, 33 questions, one laptop. Our full write-up of the test has the other results.
What we take from it is simple. Copy the dose from the official table, not from an AI answer. We're building Waystone, an offline preparedness assistant that is still in development, and this is why we plan for it to show the official passage next to any number it gives.
Before you need it
- Read the strength on your bottle and write it on the bottle.
- Keep a clean dropper next to it.
- Print the table. Our printable emergency binder has the EPA table on a page you can fill in.
- Work out how much water you need to treat with the emergency water calculator.