How much bleach to purify water: calculator
The EPA says to add 8 drops of regular, unscented 6% bleach per gallon of water, or 6 drops if your bleach is 8.25%. Stir it and let it stand for 30 minutes. If the water is cloudy, colored or very cold, the EPA says to double the dose. Enter your amount below for the exact number of drops.
After a flood or a water main break, tap water can carry germs that make people sick, and the CDC has guidance on making water safe in an emergency. If the stores are out of bottled water, a bottle of bleach and this calculator are how you make your own.
Work out your dose
Doses from the EPA table: 8 drops per gallon of 6% bleach, 6 drops per gallon of 8.25% bleach, doubled for cloudy, colored or very cold water. Teaspoons follow the EPA's 8-gallon row, rounded up to the nearest 1/8 teaspoon. Regular, unscented chlorine bleach only.
Step by step
- Settle and filter cloudy water first. The EPA says to let it settle, then filter it through a clean cloth, paper towel or coffee filter.
- Check the label. Use regular, unscented chlorine bleach and note whether it is 6% or 8.25%.
- Add the drops from the calculator and stir.
- Wait 30 minutes. The EPA says the water should have a slight chlorine smell.
- No smell? The EPA says repeat the dose and let it stand another 15 minutes.
The EPA table
| Water | 6% bleach | 8.25% bleach |
|---|---|---|
| 1 quart or liter | 2 drops | 2 drops |
| 1 gallon | 8 drops | 6 drops |
| 2 gallons | 16 drops (1/4 tsp) | 12 drops (1/8 tsp) |
| 4 gallons | 1/3 tsp | 1/4 tsp |
| 8 gallons | 2/3 tsp | 1/2 tsp |
Source: EPA, Emergency Disinfection of Drinking Water.
Common mistakes
- Using scented or color-safe bleach. The EPA table is for regular, unscented chlorine bleach.
- Drinking it straight away. The EPA says stir and wait 30 minutes.
- Using the normal dose on cloudy water. The EPA says double it, and filter the water first.
Gear for this
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Unscented regular bleach
Check the label says 6% or 8.25% sodium hypochlorite so you know which dose to use.
Medicine droppers
Counting drops from a big jug is guesswork. A dropper makes the dose exact.
Food-grade water jugs
Treat and store in the same clean container.
Questions people ask
How many drops of bleach per gallon of water?
The EPA says 8 drops of 6% bleach or 6 drops of 8.25% bleach per gallon. Double it for cloudy, colored or very cold water.
How long do you wait after adding bleach to water?
The EPA says 30 minutes. If you can't smell a slight chlorine odor, repeat the dose and wait another 15 minutes.
Can I use any bleach?
The EPA's dosing is for regular, unscented chlorine bleach. Check the strength on the label.
Sources
Related entries
- W-01How to make water safe to drink in an emergencyBoil it, bleach it, or filter and treat it. Exact amounts from the CDC.
- W-02How much water to store for an emergency1 gallon per person per day. Work out your household total in 10 seconds.
- W-03Emergency water sources in your homeYour water heater, pipes, ice and toilet tank hold water you can use. What to avoid.
General safety information only, not medical or professional advice. Rules can change, so check the linked sources and follow your local officials. As an Amazon Associate I earn from qualifying purchases.