Sodium Hypochlorite or Bleach – Sodium hypochlorite or commonly known as household bleach,is a salt of hypochlorous acid and has the chemical formula NaOCl.  Chlorine bleach is a powerful disinfectant that is inexpensive, easy to obtain, and strong enough to kill most germs. Hypochlorites exert their germicidal activity by inactivating vital bacterial enzymes.  Sodium hypochlorite and chlorine do not deactivate Giardia Lambia or Cryptosporidium. Sodium hypochlorite should be used with caution, with a pH of 11- 13, it burns and is caustic (corrosive). It is poisonous for water organisms; it is mutagenic and very toxic when it comes in contact with ammonium salts (Amonia products). Bleach  also emits potentially harmful fumes, so it should always be used in a well ventilated area.

Shelf Stability - bleach has a half-life (time it takes for 5.25% bleach solution to end up at 2.63% active) of about six months, assuming it is stored under ideal conditions (dark room, 70 degrees Fahrenheit, unopened bottle). Once opened, its shelf life/half-life drops dramatically.

 Chlorine bleach solution begins to lose its disinfectant power quickly when exposed to heat so always use cold water when mixing. It also loses its disinfecting power when exposed sunlight, and its strength is affected by the presence of organic matter and the pH or alkalinity of the water used in dilution. In order to be sure your solution is still strong enough to kill germs, you should mix a fresh batch each day and discard whatever amount you don’t use at the end of the day.


Mode of Action - The exact mechanism by which free chlorine destroys microorganisms has not been elucidated. Inactivation by chlorine can result from a number of factors: oxidation of sulfhydryl enzymes and amino acids; ring chlorination of amino acids; loss of intracellular contents; decreased uptake of nutrients; inhibition of protein synthesis; decreased oxygen uptake; oxidation of respiratory components; decreased adenosine triphosphate production; breaks in DNA; and depressed DNA synthesis 329, 347. The actual microbicidal mechanism of chlorine might involve a combination of these factors or the effect of chlorine on critical sites 347.


Microbicidal Activity - Low concentrations of free available chlorine (e.g., HOCl, OCl-, and elemental chlorine-Cl2) have a biocidal effect on mycoplasma (25 ppm) and vegetative bacteria (<5 ppm) in seconds in the absence of an organic load 329, 418. Higher concentrations (1,000 ppm) of chlorine are required to kill M. tuberculosis using the Association of Official Analytical Chemists (AOAC) tuberculocidal test 73. A concentration of 100 ppm will kill ≥99.9% of B. atrophaeus spores within 5 minutes 541, 542 and destroy mycotic agents in <1 hour 329. Acidified bleach and regular bleach (5,000 ppm chlorine) can inactivate 106 Clostridium difficile spores in <10 minutes 262. One study reported that 25 different viruses were inactivated in 10 minutes with 200 ppm available chlorine 72. Several studies have demonstrated the effectiveness of diluted sodium hypochlorite and other disinfectants to inactivate HIV 61. Chlorine (500 ppm) showed inhibition of Candida after 30 seconds of exposure 54. In experiments using the AOAC Use-Dilution Method, 100 ppm of free chlorine killed 106–107 S. aureus, Salmonella choleraesuis, and P. aeruginosa in <10 minutes 327. Because household bleach contains 5.25%–6.15% sodium hypochlorite, or 52,500–61,500 ppm available chlorine, a 1:1,000 dilution provides about 53–62 ppm available chlorine, and a 1:10 dilution of household bleach provides about 5250–6150 ppm.,

When using bleach as a disinfectant,  a 1:10 solution, 1 part bleach to 9 parts of water, is recommended.  Here are some examples for different amounts.


¼ cup bleach and 2 ¼ cup water

½ cup bleach with 4 ½ cups water

¾ cup bleach with 6 ¾ cup water


Household bleach (5.25% or 6.00%–6.15% sodium hypochlorite depending on manufacturer) usually diluted in water at 1:10 or 1:100. Approximate dilutions are 1.5 cups of bleach in a gallon of water for a 1:10 dilution (~6,000 ppm) and 0.25 cup of bleach in a gallon of water for a 1:100 dilution (~600 ppm). Sodium hypochlorite products that make pesticidal claims, such as sanitization or disinfection, must be registered by EPA and be labeled with an EPA Registration Number.

Bleach Solution


Chlorine (ppm)














Clorox I gallon around  $5.00

Generic bleach 1 gallon – around $ 3.00 -$ 5.00



Last Edited By: Matt Morris and David Newman Oct 24 15 2:05 PM. Edited 1 time.