Reasons to decontaminate:
(1) disruption of service with introduction of environmental water
(2) cross-connection with a sewage line
Options to clean the system:
(1) heat treatment
(2) chlorination
General steps:
(1) The source of contamination must be corrected and the source of clean water restored.
(2) The decontamination should be done as soon as possible when the fewest people are around. This can be done at night, over the weekend or after dismissing people for the day.
(3) Determine the probable pathogens in the system. If chlorine-resistant organisms such as Cryptosporidium are present, then the heat treatment should be used.
Heat treatment:
(1) The hot water temperature should be raised to 160 - 170°F (71 - 77°C).
(2) Each outlet should be flushed for at least 5 minutes.
(3) The temperature can be reduced once the entire system has been treated and flushed.
(4) If Cryptosporidium is present then make sure the lines are thoroughly flushed.
Chlorination:
(1) Raise the chlorine concentration so that the free chlorine is >= 2 mg/L water (>= 2 parts per million or ppm).
(2) Flush each outlet until a chlorine odor is detected.
(3) Maintain for the elevated chlorine level for at least 2 hours but no more than 24 hours.
Hazards:
(1) Thermal burns if heated water method used.
(2) Chlorine gas exposure if chlorination used.
(3) Infection if decontamination inadequate for organisms.
