Page 368 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

JWCL344_ch09_297-332.qxd 8/2/10 9:54 PM Page 328

328 Chapter 9 Cross-Connection Control
Figure 9.29 Cross- Air conditioning cooling tower
Connection Preventers

Fixture outlet Post mix
protective beverage Reduced pressure zone
devices machine backflow preventer

Backflow preventer Internal protection
with intermediate devices
atmospheric vent

Laboratory faucet double
check valve with Reduced
intermediate vacuum breaker pressure zone
backflow
preventer

Process tank
Laboratory sinks

Reduced
Atmospheric pressure zone
vacuum backflow Photo
breaker
preventer developing
equipment
Dishwasher

Hose Double check valve
vacuum backflow
breaker preventer
Cafeteria
cooking
Slop sink kettle

Reduced pressure Reduced pressure
Dedicated zone backflow zone backflow
line preventer preventer Boiler

Containment device

If the water supplier elects to protect its customers on a domestic internal protective
basis and/or “fixture outlet protective basis,” then cross-connection control protective
devices are placed at internal high hazard locations as well as at all locations where
cross-connections exist at the “last free-flowing outlet.” This approach entails extensive
cross-connective survey work on behalf of the water superintendent as well as constant
policing of the plumbing within each commercial, industrial, and residential account.