Figure 4-21. - Fire hydrant installation.

Hypochlorite solution is usually applied by measuring pumps, gravity-feed mechanisms, or portable pipe disinfecting units.

When applying disinfectants, use the following procedures:

Before adding disinfectant, flush the section thoroughly with water until dirt and mud are removed. A velocity of at least 3 feet per second is required for adequate scouring.

Stop all branches and other openings with plugs or heads properly braced to prevent blowouts.

Disinfect the water mains in sections and feed the disinfecting agent through a tap or hydrant at the end of each section. When a portable gas chlorinator or hypochlorinator is available, feed the discharge from the chlorinator into an auxiliary waterline leading to one of the hydrants or taps.

Bleed the air from the line at high points and crowns. Add the predetermined chlorine dosage as the 4-16