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Chlorine Disinfection Time Table

Time table for killing common illness-causing germs

Free chlorine at neutral pH kills most bacteria such as E. coli 0157:H7 in less than a minute if the free chlorine is maintained at proper disinfection levels throughout the pool. However, a few germs are moderately (Giardia, Hepatitis A) to highly (Cryptosporidium) chlorine-resistant. The table below shows the approximate disinfection times for these germs in chlorinated water.

Agent Disinfectant Times for Fecal Contaminants in Chlorinated Water*
E coli 0157:H7
Bacterium		 < < 1 minute
Hepatitis A
Virus 		approximately 16 minutes
Giardia
Parasite		 approximately 45 minutes
Cryptosporidium
Parasite		 approximately 15300 minutes (10.6 days)
  • 1 mg/L (1ppm) free chlorine at pH 7.5 and 25o C (77o 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.