Disinfection for Pipeline Repairs - Disinfection of Pipelines and Storage Facilities Field Guide - page 60

Courtesy Denver Water
Figure 4-1 Excavation dewatering for pipeline repair

to reduce potential pollution. Calcium hypochlorite tablets are
used for this application because they dissolve slowly, continu-
ously releasing chlorine as the repair is completed.
Chlorine solution (1 percent hypochlorite prepared according
to Table 3-11) should be applied to the interior of pipe and fit-
tings used for pipeline repair. The solution can be swabbed with
an applicator or sprayed (Figure 4-2) on the interior surfaces of
the pipeline and repair parts.
The section of repaired main should be disinfected whenever
possible. The slug method (Chapter 3) is usually used because it
takes less time to accomplish. The repaired section is isolated, all
service connections shut off, and then the main is flushed before
chlorinating. The chlorine dose may be as much as 300 mg/L
(Table 4-1) and the contact time as short as 15 min. Calcium
hypochlorite granules or tablets require some time to dissolve.
Therefore, this chemical may not be the best choice if the main