sounding tube. The addition of water should provide sufficient mixing of the chlorine solution
in the tank.
(5) Allow the treated water to set for 30 minutes then test for adequate FAC residual in the
system using the chlorine test kit. If the test reveals an FAC of less than 1.0 ppm, the entire
process must be repeated until this residual remains. Unexpectedly low F AC residual levels
occur when organic materials in the system exert a demand on the available chlorine. If the
FAC chlorine residual is at least 1.0 ppm, the water may be used.
b. In cases where a 5 ppm FAC residual is required, the procedure outlined in "a" above should be
followed, appropriately adjusting the chlorine dosage.
c. If it is determined that contamination of the potable water supply exists, the potable water tank has
been entered for maintenance or repair, or the potable water tank has been filled with non-potable
water (such as for ballasting), superchlorination of the potable water tanks must be accomplished. The
superchlorination procedure is similar to the disinfection procedure, but an increased amount of
chlorine is utilized over a longer period of time. Superchlorination is to be performed in accordance
with the following steps:
(1) Determine the capacity of the tank in gallons.
(2) Using the chlorine dosage chart (Table B-2), determine the amount of chlorine necessary to
obtain 100 ppm chlorine in the potable water tank.
(3) Mix the chlorine in warm water. Allow the mixture to settle before introducing into the
potable water tank.
(4) Completely fill the potable water tank with water to ensure adequate mixing. Allow the
mixture to set for 4 hours.
(5) After 4 hours, determine if chlorine residual exists. If there is no chlorine residual, drain
the contents of the potable water tank and repeat steps (1) through (4).
(6) After 4 hours, if chlorine residual exists, drain the contents of the potable water tank and
refill the tank with potable water. The potable water distribution system may now be used.
d. Mechanical cleaning and chemical disinfection of the potable water tanks may be required under
(1) When extensive repairs have been completed.
(2) When sludge or rust accumulations impair the quality of water.
(3) When the tanks have been loaded with contaminated water (such as for ballast).