8 drops
Per Gallon (6%)
30 min
Wait Time
2x
If Cloudy Water
The correct bleach to water ratio is 8 drops of 6% bleach per gallon of clear water (or 6 drops of 8.25% bleach). Double the dose for cloudy water. Wait 30 minutes. If there's no faint chlorine smell, repeat the dose and wait 15 more minutes. This is the EPA-recommended emergency method.
Knowing the right bleach to water ratio could save your life in an emergency. Whether you're prepping 55-gallon drums, treating creek water on a camping trip, or purifying tap water after a boil advisory, the ratios below are what the EPA, CDC, and WHO recommend.
Most sites give you one or two numbers and leave it at that. This guide covers every volume from a single quart to a 55-gallon barrel, for both bleach concentrations you'll find at the store, in both clear and cloudy water scenarios. For a deeper dive into long-term water planning, see our water storage guide for a family of 4.
According to the CDC, if your water supply may be contaminated, do not use untreated water for: drinking, cooking, washing dishes, brushing teeth, washing hands, making ice, making baby formula, or bathing open wounds. Treat or boil all water first, even for non-drinking uses.
Boiling: The First Choice for Water Purification
Before reaching for the bleach bottle, know this: boiling is the single most reliable method to make water safe to drink. Every major health authority (EPA, CDC, WHO) lists it as the primary recommendation.
Rolling Boil for 1 Minute
Bring water to a full, rolling boil and maintain it for 1 minute. At elevations above 6,500 feet (2,000 meters), boil for 3 minutes because water boils at a lower temperature at altitude.
Kills Everything Including Cryptosporidium
Boiling kills bacteria, viruses, and parasites including Cryptosporidium and Giardia. This is a critical advantage over bleach, which does not reliably kill Cryptosporidium.
Pre-Filter Cloudy Water
Before boiling, filter cloudy water through a clean cloth, coffee filter, or paper towel. This removes sediment and improves the effectiveness of any treatment method.
Boiled water tastes flat because the dissolved oxygen has been driven off. To restore the taste, add a pinch of salt per quart or pour the cooled water back and forth between two clean containers several times to re-aerate it.
When boiling isn't an option — no fuel, no pot, no time — bleach is your best chemical alternative. It's cheap, widely available, and effective against bacteria and viruses. The rest of this guide covers exactly how to use it.
Quick Reference: Bleach to Water Ratio
Memorize this for emergencies. These numbers are for regular 6% bleach, which is the most common concentration:
"You must be 21 to drink" - 2 drops per 1 quart. From there, multiply: 1 gallon = 4 quarts = 8 drops. Five gallons = about half a teaspoon. Easy to remember under stress.
Complete Bleach to Water Ratio Chart
This table covers both common bleach concentrations. Most store-bought bleach today is 8.25%, but check your label. Older bottles may be 5.25-6%.
For Clear Water
| Water Volume | 6% Bleach | 8.25% Bleach |
|---|---|---|
| 1 quart (1 liter) | 2 drops | 2 drops |
| 1/2 gallon (2 liters) | 4 drops | 3 drops |
| 1 gallon (4 liters) | 8 drops | 6 drops |
| 2 gallons | 16 drops (1/4 tsp) | 12 drops (1/8 tsp) |
| 5 gallons | 1/2 teaspoon | 1/4 teaspoon |
| 10 gallons | 3/4 teaspoon | 1/2 teaspoon |
| 20 gallons | 1-1/2 teaspoons | 1 teaspoon |
| 55 gallons (drum) | 4 teaspoons | 2-1/2 teaspoons |
For Cloudy, Colored, or Very Cold Water
Double the dose. Organic matter and sediment use up chlorine before it can kill pathogens. Cold water (below 40°F) slows the disinfection process.
| Water Volume | 6% Bleach | 8.25% Bleach |
|---|---|---|
| 1 quart (1 liter) | 4 drops | 4 drops |
| 1 gallon | 16 drops (1/4 tsp) | 12 drops (1/8 tsp) |
| 2 gallons | 1/2 teaspoon | 1/4 teaspoon |
| 5 gallons | 1 teaspoon | 1/2 teaspoon |
| 10 gallons | 1-1/2 teaspoons | 1 teaspoon |
| 55 gallons (drum) | 8 teaspoons | 5 teaspoons |
If water is visibly cloudy, filter it first through a clean cloth, coffee filter, or paper towel. Let sediment settle, then pour off the clear water. Then apply the cloudy water dose. Filtering removes large particles; bleach handles the bacteria and viruses.
Which Bleach to Use (and Which to Avoid)
Not all bleach is safe for water purification. Using the wrong type can make you sick.
Safe to Use
- ✓Regular unscented bleach (5.25-8.25% sodium hypochlorite)
- ✓Label says "sanitization" or "disinfection"
- ✓Only active ingredient: sodium hypochlorite
- ✓Less than 1 year old (stored in cool, dark place)
Never Use
- ✗Scented bleach (lemon, lavender, etc.)
- ✗"Splash-less" or "no-splash" formulas
- ✗Color-safe or oxy bleach
- ✗Bleach with added cleaners or surfactants
Flip the bottle over and read the active ingredients. It should say "Sodium Hypochlorite" and nothing else under active ingredients. The concentration (5.25%, 6%, or 8.25%) will be listed there too. This is the number you need for the charts above.
Step-by-Step: How to Treat Water with Bleach
Filter If Needed
If water is cloudy or has visible particles, let it settle then pour through a clean cloth, coffee filter, or bandana. This isn't optional for cloudy water - sediment uses up chlorine and prevents proper disinfection.
Add the Correct Amount of Bleach
Use a clean dropper for small quantities. For larger volumes, use a measuring spoon. Refer to the charts above based on your water volume, water clarity, and bleach concentration.
Stir and Wait 30 Minutes
Mix thoroughly and let the water sit for 30 minutes. For cloudy or cold water (below 40°F), wait a full 60 minutes. The chlorine needs time to kill bacteria, viruses, and most protozoa.
Smell Test
The water should have a faint chlorine smell (like a swimming pool, but much milder). If there's no chlorine odor at all, add the same dose again and wait another 15 minutes.
Reduce Chlorine Taste (Optional)
If the chlorine taste is too strong, pour the water back and forth between two clean containers a few times. This aerates the water and dissipates excess chlorine. Letting it sit uncovered for a few hours works too.
Bleach kills bacteria, viruses, and most protozoa (like Giardia). It does not remove chemical contaminants, heavy metals, pesticides, or salt. It also does not reliably kill Cryptosporidium. If you suspect chemical contamination, bleach treatment is not enough. Boiling is more effective against Crypto. For chemical contamination, you need activated carbon filtration.
Bleach for Long-Term Water Storage
Storing water long-term is different from emergency purification. If you're filling containers with already-treated municipal tap water, you need a maintenance dose - just enough chlorine to prevent bacterial regrowth over months of storage.
| Container | 6% Bleach | 8.25% Bleach |
|---|---|---|
| 1 gallon jug | 1/8 teaspoon | 1 drop |
| 5 gallon carboy | 1/4 teaspoon | 4-5 drops |
| 7 gallon Aquatainer | 1/3 teaspoon | 6-7 drops |
| 55 gallon drum | 1/3 teaspoon | 1/4 teaspoon |
Notice the storage doses are much smaller than purification doses. That's because you're starting with already-clean water - you just need enough residual chlorine to prevent anything from growing during storage. For untreated water sources (wells, springs, rainwater), use the full purification dose from Section 2.
For complete guidance on how much water to store for your household, see our Emergency Water Storage Guide.
Common Mistakes That Make Bleach Treatment Fail
Using Old Bleach
Bleach degrades over time. A bottle that's been sitting in your garage for 2 years may have lost half its strength. Rotate your bleach every 6-12 months. If you can't smell chlorine in the bottle, it's probably too weak. When in doubt, double the dose.
Not Waiting Long Enough
Chlorine doesn't kill instantly. The 30-minute wait isn't a suggestion - it's the minimum contact time needed to kill most bacteria and viruses. In cold water, you need 60 minutes. Drinking too soon means the chlorine hasn't finished its job.
Skipping the Smell Test
After 30 minutes, you should detect a faint chlorine odor. No smell means all the chlorine was consumed by organic matter before it could finish disinfecting. The water is not safe. Add another dose and wait 15 more minutes.
Using the Wrong Bleach Concentration
Most bleach sold today is 8.25% sodium hypochlorite, but the old "8 drops per gallon" rule was based on 5.25-6% bleach. If you use the old dosage with modern concentrated bleach, you're over-treating. It won't hurt you, but it tastes worse. Check the label and use the right column in the chart above.
Treating Chemically Contaminated Water
Bleach kills biological threats. It does nothing against chemical contamination (fuel spills, pesticide runoff, industrial waste). If you suspect chemical contamination, you need activated carbon filtration or an alternative water source. Don't assume bleach-treated water is safe to drink in every scenario.
Alternative Disinfection Methods
Bleach is widely available, but it's not your only option. Each method below has trade-offs in effectiveness, shelf life, and ease of use.
Calcium Hypochlorite (Pool Shock)
Best for StockpilingDry powder with a 10+ year shelf life — far longer than liquid bleach. Dissolve 1 heaping teaspoon of 68-70% calcium hypochlorite in 2 gallons of water to create a stock solution. Use 1 pint of this stock solution per 12.5 gallons of water to treat. Store the dry powder in a sealed, airtight container away from heat and moisture.
Iodine
Add 5 drops of 2% tincture of iodine per quart of clear water, or 10 drops for cloudy water. Wait 30 minutes before drinking. Not recommended for pregnant women or people with thyroid conditions. Best as a short-term or backup method.
Chlorine Dioxide Tablets
Follow manufacturer instructions (brands like Aquamira, Potable Aqua ClO2). The key advantage: chlorine dioxide kills Cryptosporidium, which bleach does not. The downside is a longer wait time — typically 4 hours for full effectiveness against Crypto. Great for backpacking and emergency kits.
UV Purifiers (SteriPEN, etc.)
Battery-operated UV wands treat water in about 90 seconds per bottle (typically 1 liter). Effective against bacteria, viruses, and protozoa. Requires clear water (pre-filter if cloudy) and charged batteries. No chemical taste. Good for travel and short-term emergencies.
Solar Disinfection (SODIS)
Fill a clear PET plastic bottle with water and place it in direct sunlight for 6+ hours (or 2 full days if cloudy). UV-A radiation and heat inactivate pathogens. Free and requires no supplies beyond a plastic bottle, but slow and weather-dependent. Best as a last resort when no other method is available.
The best emergency water plan uses multiple methods. Stock calcium hypochlorite for long-term storage, keep a UV purifier for quick treatment, and know how to boil as your failsafe. Redundancy matters when your health depends on it. See our water purification calculator for precise bleach dosing.
Emergency Water Treatment Supplies Checklist
Keep these items together in your emergency kit so you're ready to treat water at a moment's notice. Check and rotate supplies every 6 months.
Under 12 months old, 6% or 8.25% sodium hypochlorite. Check the date and replace annually.
A medicine dropper for small volumes. 1/4 tsp and 1/2 tsp measuring spoons for larger batches.
Food-grade plastic or glass. Never use containers that held chemicals, milk, or juice.
For pre-filtering cloudy water before treatment. A bandana or clean t-shirt works in a pinch.
Label every container with the treatment date and method. In a crisis, you will forget which water is treated.
For a complete emergency water plan including storage containers, rotation schedules, and family sizing, read our Emergency Water Storage Guide.
Frequently Asked Questions
How much bleach do I add to 1 gallon of water to purify it?
For 6% bleach (standard): add 8 drops per gallon of clear water, or 16 drops for cloudy water. For 8.25% bleach (concentrated): add 6 drops per gallon of clear water, or 12 drops for cloudy water. Let stand 30 minutes. The water should have a faint chlorine smell.
Can you use any bleach to purify water?
No. Only use regular, unscented liquid bleach with sodium hypochlorite as the sole active ingredient (5.25-8.25%). Never use scented bleach, splash-less bleach, color-safe bleach, or bleach with added cleaners or surfactants. Check the label - it should say "sanitization" or "disinfection" as a listed use.
How long do you wait after adding bleach to water?
Wait at least 30 minutes for clear water, or 60 minutes for cloudy or cold water. After waiting, the water should smell faintly of chlorine. If there is no chlorine smell, add the same amount of bleach again and wait another 15 minutes. A faint chlorine odor means the treatment worked.
How much bleach for a 55-gallon water barrel?
For long-term storage of already clean municipal water: add 1/4 teaspoon of 8.25% bleach (or 1/3 teaspoon of 6% bleach) per 55 gallons. For purifying untreated water: add 1 teaspoon of 8.25% bleach (or 1-1/3 teaspoons of 6% bleach) per 55 gallons. Storage doses are lower because the water is already treated.
Does bleach expire for water purification?
Yes. Bleach loses about half its strength after 6-12 months of storage. Fresh bleach (under 6 months old) works best. If your bleach is over a year old, double the dose. If it is more than 2 years old, replace it. Store bleach in a cool, dark place to slow degradation.
Can I use pool shock (calcium hypochlorite) instead of bleach?
Yes. Calcium hypochlorite is actually better for long-term storage — dry powder keeps potency for 10+ years vs liquid bleach's 6-12 months. To make a stock solution, dissolve 1 heaping teaspoon of 68-70% calcium hypochlorite in 2 gallons of water. Then use 1 pint of this stock solution per 12.5 gallons of water to treat.
Is bleach-treated water safe to drink?
Yes, when dosed correctly. The 6-8 drops per gallon produces about 5 ppm free chlorine, which drops as it reacts with contaminants. The EPA maximum for safe drinking water is 4 ppm. After 30 minutes, the concentration is well within safe limits — the same chlorine used in municipal tap water.
How long does bleach-treated water stay safe to drink?
Sealed in a clean container, bleach-treated water is safe for 24-48 hours at room temperature. Refrigerated, it lasts up to a week. For longer storage, re-treat with a maintenance dose of 2 drops per gallon every 6 months.
Can I purify water with iodine instead of bleach?
Yes. Add 5 drops of 2% tincture of iodine per quart of clear water, or 10 drops for cloudy water. Wait 30 minutes before drinking. Warning: iodine should not be used by pregnant women or people with thyroid conditions. Chlorine dioxide tablets are a better alternative that also kills Cryptosporidium.
Sources
- EPA: Emergency Disinfection of Drinking Water - Primary dosage reference for 6% and 8.25% bleach
- CDC: Making Water Safe in an Emergency - Contact time and repeat dosage guidance
- WHO: Guidelines for Drinking-Water Quality (4th edition) - Chlorine residual and contact time requirements
- Washington State DOH: Water Purification - State-level guidance for emergency water treatment
For complete planning on storing, treating, and rotating your water supply, see our Emergency Water Storage Guide covering container types, storage duration, and family sizing.
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