How to Properly Dilute Bleach (and Why You Should Never Use Hot Water)
Bleach is an excellent disinfectant, but safety is important. You already know that you cannot mix it with ammonia, vinegar or alcohol , but did you know that the temperature of the water also matters? Here’s a guide to properly diluting bleach so it can be used as a disinfectant. Spoiler: many of you are doing it wrong.
Why dilute bleach?
If you want to disinfect a surface with bleach, diluting the bleach with water is actually more effective than using it alone . Diluted bleach is also gentler on the materials it comes into contact with, saving you money and trouble—a bottle of bleach can last a very long time if you only use a few tablespoons at a time.
Use cold or room temperature water.
When washing clothes with soap, we usually use warm or hot water because the heat energy helps chemical molecules interact with each other more often. If you’ve ever washed dishes with cold water at a campsite and hot water in the sink at home, you already know the difference.
But when it comes to disinfecting with bleach, the higher temperature isn’t worth the downside. Using hot water isn’t dangerous, nor are some of the other things people do with bleach (please don’t put it on your skin ), but it does have some distinct downsides.
First, a hot bleach solution with steam will likely allow some of the bleach to become airborne. Bleach fumes can irritate your eyes and nose, so you should always use bleach in a well-ventilated area if possible. Using water at room temperature will minimize this effect.
Another problem is that hot water speeds up the breakdown of the chemicals in bleach . Even a properly prepared bleach solution will be less effective if you leave it overnight, so you should make a fresh solution every day. If you need a bucket of diluted bleach to last you through a day’s cleaning, it will retain its effectiveness better in warm water than in hot water.
However, there is one situation where hot water is fine, and that is laundry. Clorox says clothes can be washed in hot water and bleach, and the heat may even help the bleach work faster. Concerns about fumes and loss of efficiency are not relevant when the bleach is inside the washing machine for the short period of time needed to wash socks.
Use the right bleach
You’ll find many things marketed as “bleaches,” such as color-safe bleach, splash-free bleach, Clorox brand cleaning solutions, and more. When we talk about using bleach to disinfect things, we’re talking about regular household bleach (like this one ) with the active ingredient 8.25% sodium hypochlorite. In the dilution instructions below, the CDC recommends using bleach with a sodium hypochlorite concentration of 5 to 9%. If it doesn’t give you a percentage, don’t use it. And if the percentage is outside the 5-9% range, either don’t use it or look for the appropriate dilution rate from the manufacturer or another source.
Mix bleach and water in the correct ratio.
Do not pour a batch of bleach into a bucket of water. Measure . The CDC recommends the following ratios when using standard household bleach:
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5 tablespoons per gallon of room temperature water or
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4 teaspoons per liter of water at room temperature
Note the difference in units: if you measure by gallon, you use five tablespoons. This is a little more than a quarter glass. (If you’ve heard that you should use 1/3 cup per gallon of water, that’s basically the same as this rule. Close enough.)
On the other hand, for a quart it means four teaspoons . If you mix a smaller amount for a spray bottle, two teaspoons will make 16 ounces. It’s simple math if you remember the common kitchen units: three teaspoons per tablespoon, four tablespoons per quarter cup, two cups per pint, two pints per quart, four quarts per gallon. I realize not everyone remembers this, so here’s a handy chart from Clorox that shows the appropriate sizes for different sized buckets and sprayers.
Store it correctly
Diluted bleach does not last forever. If you mix it in a bucket right before use and immediately pour the rest down the drain, you don’t have to worry about storage. But if you’re preparing a product to use throughout the day, such as in a spray bottle, pour it out at the end of the day .
The bleach breaks down once diluted, and the solution is only good for about 24 hours. The same sprayer will not be effective for disinfection the day after tomorrow. Bleach solutions also break down more quickly when exposed to sunlight, so if you are storing the solution temporarily, use an opaque container.