Purpose: Calculate the proper volume of bleach needed for a sanitation solution.
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Bleach (sodium hypochlorite) is a very cheap and effective sanitizer, but it has a bad reputation due to the strong odor and flavor. A common problem with bleach is that homebrewers use way too much. Older recommendations, such as one to two ounces per five gallons (Papazian, 1984, p. 22), may have been good advice a few decades ago but this amount could be overkill with today's more highly concentrated bleach.
The flavor and odor problems associated with using bleach as a sanitizer can be greatly decreased by using the proper concentration needed for effective sanitation. Bleach is very strong, so only small amounts are needed to make an effective sanitizing solution. The general recommendation is 50 to 100 parts per million (ppm) for sanitizing equipment that will come into contact with food. Stronger concentrations such as 100 to 200 ppm are sometimes used in conditions with heavy soiling or organic matter. Concentrations over 200 ppm are considered to be unsafe.
This calculator uses the bleach concentration percentage to determine the amount needed to make a solution at a specific ppm concentration. The basic formula of M1V1 = M2V2 is from this distance education web site on water management. Rearranaging this formula for the needed bleach yields the following formula: bleachvolume = (targetppm * targetvolume) / bleachppm.
Charlie Talley of Five Star Chemicals recommends adding small amounts of vineagar to bleach-based sanitizing solutions to slightly lower the pH to about 5 or 6 (podcast from Better Brewing Radio). The lower pH helps bleach to be more effective at a lower concentration (see figure 1 from this Food Technology Fact Sheet). Talley's recommendation is for one fluid ounce of bleach and one ounce of vinegar in five gallons of sanitizing solution. You might need more vinegar to reach a pH of 5 to 6 if your water is somewhat alkaline.
Weak bleach sanitizer solutions can be described as no-rinse in the sense that it is safe to use without rinising at these concentrations. This is not, however, a good idea in regard to flavor. My experience is that the residue from these low concentration solutions can still be tasted in the final product. To avoid these off flavors, the recommendation is to rinse the sanitizing solution from equipment with chlorinated tap water or water that has been boiled to kill bacteria. Rinsing with city tap water that is chlorinated at 1 ppm seems to work well. If you use the recommended concentration of 50 to 100 ppm it should not be necessary to "triple-rinse" like some older sources suggest. The need for three rinses is really a sign that far too much bleach was used.
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