Bleach – Water Ratio For Drinking Water Purification

If your water source is uncertain, you should treat it first before drinking it.

One way to treat water for drinking is to add a small amount of Regular Bleach (chlorine). Here’s how much regular bleach to add:
(details below)

One best way to purify water for drinking is to boil it for 1 minute.

[ Read: How Long to Boil Drinking Water until Safe or Disinfected ]

Once the water has reached a rolling boil, it has become safe to drink.

Note that if the water source had been contaminated with chemicals, boiling it or otherwise treating it will NOT assure that the chemical is removed.

Know your water source as best you can.

Another way to purify water is to use a small amount of Regular liquid bleach.

Use Regular household bleach, with the only ‘active’ ingredient ‘sodium hypochlorite’.

UPDATE: For many years Regular bleach contained a concentration of 5.25% sodium hypochlorite. Newer ‘Regular’ liquid bleach (which has been available for several years) now contains a concentration of 8.25% sodium hypochlorite (about 57% more than the original bleach formula).

(I have listed both amounts below for your reference.)

Having recently determined how much bleach to add to a 50-gallon water tank to purify it for safe drinking, I’ve put together the following charts for your reference.

One old ‘saying’ – a way to remember for small quantities:

“You must be 21 to drink”

2 drops bleach per 1 quart water

Mix the following amount of bleach with water, and wait 30 minutes for it to work. The water should have just a ‘hint’ of chlorine smell.

Water – Bleach Ratio For Purification

(Bleach containing 5.25% Sodium Hypochlorite)
numbers are ’rounded’

This will initially produce ~ 5 ppm chlorine

1 Quart water, 2 drops bleach
1 Gallon water, 8 drops bleach
5 Gallons water, 1/2 teaspoon bleach
10 Gallons water, 3/4 teaspoon bleach
50 Gallons water, 4 teaspoons bleach

Water – Bleach Ratio For Purification

(Bleach containing 8.25% Sodium Hypochlorite)
numbers are ’rounded’

This will initially produce ~ 5 ppm chlorine

1 Quart water, 1 drop bleach (1.3 rounded)
1 Gallon water, 5 drops bleach
5 Gallons water, 1/4 teaspoon bleach
10 Gallons water, 1/2 teaspoon bleach
50 Gallons water, 2-1/2 teaspoons bleach

Read more: Smallest Berkey Countertop Water Filter – Specs
Big Berkey

(More details here)


The initial chlorine level (ppm) will drop when interacting with water and organic contaminants (it’s doing it’s job). This may occur slowly or precipitously.

If the water is cloudy, and if you still cannot smell any chlorine in the water after having let it sit for 30 minutes (there should be a hint of chlorine smell), the CDC (Centers for Disease Control) advises that you consider a 2nd round of treatment.

According to the EPA, the maximum recommended ppm (parts per million) of chlorine bleach in drinking water is apparently 4 ppm.

Generally speaking, water that has a chlorine level of 4 ppm would smell very strong of chlorine, whereas a ‘hint’ of smell indicates a level well below that. A chlorine test kit is the only true way to know for sure.

Bleach will lose its potency (fairly quickly) over time. Generally, 6 months to a year after its expiration date may result in half strength.

[ Read: How Much Bleach for Disinfecting Surfaces (Food & Non-food Surfaces) ]

[ Read: How Much Chlorine Bleach To Add In My Water Storage ]

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  1. Some of your information is not correct. The lack of a chlorine smell doesn’t indicate a low chlorine level. The smell comes from a chloramine gas. After breakpoint chlorination the smell is very low. If you don’t smell the “chlorine” smell it could be you have enough. If you continue to add chlorine it will not smell more strongly. Open a bottle of bleach and take a whiff. It’s not a strong “chlorine” smell. That’s because it’s not reacting with anything. Please don’t tell people to continue adding chlorine if they can’t smell it.

    1. Jack,

      The smell check is simply subjective, and suggested per CDC instructions regarding wilderness water treatment.

      I checked the article again, and there is no instruction to continue adding chlorine if they can’t smell it. Rather, there is a suggestion for a 2nd round of treatment. That’s it. Hope that helps clear it up.

      Ultimately, a chlorine test kit will reveal the level.

        1. To Marcella,
          If the water is fairly clear without lots of sediment, then approximately 6-8 drops for regular bleach containing 5.25% sodium hypochlorite, or, about 4-6 drops for regular bleach containing 8.25% sodium hypochlorite. With that said, the more organic sediment/contaminant in the water, the more bleach/chlorine that you’ll need. But that’s a judgement call…

    2. Too much chlorine creates a burning sensation, no smell. However if you keep sniffing to double/triple check, there maybe a mucousy smell. I think that’s you smelling your own mucous – burning or breaking down slightly as it absorbs the chlorine vapor/gas. All this can lead to confusion if you don’t know it. I serviced and owned my own pool route for about 8 years. Just very carefully smell the vapors from the bleach bottle and you’ll know exactly what I mean.

        1. Yeah chlorine is not what I worry so much about in the water, it’s the fluoride. I hate it but that’s a whole different discussion that often leads to arguments and endless rabbit holes.

      1. I am a marine engineer and used bleach all the time to purify drinking water and for the waste treatment system This ship was 50 years old and yes the old original ac and refer systems were in the same room plenty of electric motors from two to a 7,000 hp main motor. There was no damage to the windings . I also ran waste water treatment plants. there was a constant drip of 15% dioxide chlorine in the clarifier and no damage to the blower motor windings. There are many residential swimming pools near ac systems and they operate fine with constant exposure to chlorine fumes. Yes chlorine in high concentrations is corrosive to many metals. The small amount needed to purify water will not harm an AC system.

      2. Oxygen is also highly corrosive to metal parts and can destroy many parts of metal machines but were still required to breath it to survive.

  2. Metric, please! The volume of one Quart or gallon varies 20% depending on the country! Only Myanmar, Liberia, and the USA are not metric.

    1. So, if only Myanmar, Liberia and the USA are not metric, how many people here are in Myanmar or Liberia? Nope, the majority are in the US. No metric, sorry.

      1. I like this discussion. In the US we do use metric. The metric is called SI.
        In engineering, designing, physics, and science it is all metric. We use metrics all the time. In fact, when I started working at the place I do now (1986) my job was to mix chemicals for gasoline and I had to do this in metric system, and then convert to English system (ounces, gallons and such).
        When I used temperature chambers, the temperature was in Celsius. I clearly understood the translation between Fahrenheit and Celsius, and the sense of oh it feels on our skin. But, at home I expect my thermometer to be in Fahrenheit, my measuring cups are English, and my stove in in Fahrenheit.
        In the US we use both systems.

        1. You say “English”, but the American gallon and the British gallon are different.

    2. Max your on the internet, there are plenty of sites using metric for your query.

      Would have taken less time than your Liberia comment :-)

  3. I’m adding a 1,000 gal. storage tank to our well water system. The draught in the SW has resulted in the aquafer to go from 147 ft. deep when our 200′ well was initially drilled 12 years ago to about 180′ feet today. And the farmers have started their pivot and hose line irrigation already. I’m installing the tank so it fills manually from the well and using a dedicated well pump in the tanks as the pressure pump that will be activated by the existing pressure switch and “pressure tank” (think accumulator). But since the opaque plastic tank is outside I came to this site for info to keep the water potable. Some good stuff here, thank you.
    BTW; one thing that has remained “English” measure is aircraft. Even though airplanes are now manufactured, and have been, by many other countries they’re made in inches and feet.

    1. Aerofxr,
      Bleach is one way. You might investigate installing an ozone generator unit on that storage tank, and running it off of a small solar panel. No supplies to be kept, the ozone generator will put enough O3 into the water to keep bacteria, algae, etc from growing in it. Just a thought.

    2. Might want to spray paint your opaque tank ( light color ) also before painting use a strip of tape top to bottom so that after painting you have a visible water mark to observe water level.

    1. @ SHEKHAR,
      According to my calculations and conversions (disclaimer: do your due-diligence), for 30,000 liters of water, add 2 liters of regular household bleach. Mix / disperse as best as possible.

    1. A little bleach is fine on the front end for water storage but to really have the ability to enjoy even you city water get a berkey water filter, use for all DRINKING WATER you will never look back.

  4. City water already has chlorine in it, so You should be good if your barrel is clean. Adding more as indicated above won’t hurt either, but likely not necessary.

  5. I would like to find a site that offers a chart that gives quantities of bleach for long-term storage of tap water, in drops, tsp, AND oz for (say) 3 most common strengths of bleach, when mixed with common amounts of water, (say) 1 qt, 1 gallon, 5 gallons, 25 gallons, and 100 gallons.
    Any recommendations?

  6. 95% of the world uses metric. almost all these web sites giving bleach to water ratios use pre-historic imperial measures so almost useless to most of the world.

    1. Well then i guess the rest of the world should either learn to convert quantities or go read how to do it one one of their own websites, 🤪

  7. gregk, if you have trouble with the measurements they have free calculators to help you change it to your preferred measure.

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