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Chlorine Disinfection Timetable

Close-up of the element chlorine on the periodic table of elements.

Timetable for killing common illness-causing germs


Free chlorine kills most bacteria such as E. coli 0157:H7 in less than a minute if it is maintained at proper disinfection levels (1-3 parts per million [ppm] free chlorine) and under ideal water conditions (pH at 7.5 or less; temperature at 77° F [25° C] or more) throughout the pool. However, a few germs are moderately (Giardia, Hepatitis A) to highly (Cryptosporidium) chlorine-tolerant. The table below shows the approximate disinfection times for these germs in chlorinated water.

Chlorine Disinfection Timetable
Agent Disinfectant Times for Fecal Contaminants in Chlorinated Water
E. coli 0157:H7
(Bacterium)
less than 1 minute
Hepatitis A
(Virus)
approximately 16 minutes
Giardia
(Parasite)
approximately 45 minutes
Cryptosporidium
(Parasite)
approximately 15,300 minutes (10.6 days)
Notes:
  • 1 mg/L (1ppm) free chlorine at pH 7.5 and 25° C (77° F)
  • These disinfectant times are only for pools that do not use chlorine stabilizers such as cyanuric acid. Disinfection times would be expected to be longer in the presence of a chlorine stabilizer.

 
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