Disinfection of Pipelines - Disinfection of Pipelines and Storage Facilities Field Guide - page 41

should be at least 25 mg/L free chlorine. Tables 3-9a, b
list the amount of chlorine required for 100 ft (30.5 m) of
pipe of various diameters. Prepare a 1 percent chlorine
solution by mixing 1 lb (454 g) of calcium hypochlorite or
3 L of 10 percent strength sodium hypochlorite solution
in 8 gal (30.3 L) of water. Use the continuous-feed rate
calculators (c3-1 to c3-5) to determine the correct match-
ing feed rate depending on the pipeline fill rate to achieve
25 mg/L chlorine dosage.
6. Measure the chlorine residual regularly to verify the con-
centration (high-range chlorine test kit or applicable
method in current edition of Standard Method for the
Examination of Water and Wastewater or AWWA Manual
M12, Simplified Procedures for Water Examination ).
Take samples for chlorine testing near the point of injec-
tion and at the end of the pipeline.
7. Retain the chlorinated water in the main for at least
24 hr. Operate valves and hydrants connected to the
treated section to ensure that they are also disinfected.
8. At the end of the 24-hr holding period, the water within
the treated main must have a chlorine residual of at least
10 mg/L free chlorine.
9. A solution-feed, vacuum-operated chlorinator (Figure 3-14)
and booster pump may be used for chlorine application.
Gasoline or electrically powered chemical-feed pumps may
be used to inject hypochlorite solutions.
10. Make sure that chlorine solution feed lines are compati-
ble with these chemicals and that the feed system can
withstand the feed pressure. The feed system must be
free of leaks.
11. Take precautions to control any water discharges (dechlo-
rination may be necessary).