Disinfection of Pipelines - Disinfection of Pipelines and Storage Facilities Field Guide - page 23

Courtesy Denver Water
Figure 3-7 Hydraulic jet cleaning

Courtesy Denver Water
Figure 3-8 Washing during pipeline repair

distribution system. Therefore, prevent backflow from newly
installed (but untested) pipelines to the active distribution system.
This can be accomplished with a physical separation (Figure 3-9)
between the systems or by the use of an approved backflow pre-
vention device. Hydrostatic pressure testing of new pipelines is
another situation when backflow is a possibility.