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.