§ 15-233 INSTALLATION.
   (a)   Generally. Approved devices shall be installed at all fixtures and equipment where backflow or back-siphonage may occur and where a minimum air gap between the potable water outlet and the fixture or equipment flood-level rim cannot be maintained. Backflow and back-siphonage devices of all types shall be in an accessible location. Installation in pits or any other location not properly drained shall be prohibited and dual check valves are not required to be installed in the meter box. Additionally, the installation of strainers shall be required and located immediately upstream of the backflow device.
   (b)   Connections not subject to back pressure. Where a water connection is not subject to back pressure, a vacuum breaker shall be installed on the discharge side of the last valve on the line serving the fixture or equipment. A list of some conditions requiring protective devices of this kind are given in the following table titled Cross Connections Where Protective Devices are Required and Critical Level (C-L) Settings for Vacuum Breakers.
Cross Connections Where Protective Devices Are Required and Critical Level (C-L) Settings for Vacuum Breakers
Fixtures or Equipment
Method of Installation
Cross Connections Where Protective Devices Are Required and Critical Level (C-L) Settings for Vacuum Breakers
Fixtures or Equipment
Method of Installation
Aspirators and ejectors
C-L at least six inches of above flood level of receptacle served
Dental units
On models without built in vacuum breakers C-L at least six inches above flood level rim of bowl
Commercial dish washing machine
C-L at least six inches above flood level of machine. Installed on both hot and cold water supply lines
Garbage can cleaning machines
C-L at least six inches above flood level of machine; installed on both hot and cold water supply lines
Hose outlets
C-L at least six inches above flood level of machine; installed on both hot and cold water supply lines.
Commercial laundry machines
C-L at least six inches above flood level of machine; installed on both hot and cold water supply lines
Lawn sprinklers
C-L at least six inches above highest sprinkler head or discharge outlet
Steam tables
C-L at least six inches above flood level rim
Tanks and vats
C-L at least six inches above flood level rim or line
Through urinals
C-L at least 30 inches above perforated flush pipe
Flush tanks
Equipment with approved ball cock, installed according to manufacturer’s instructions
Hose bibs
C-L at least six inches above flood level of receptacle served
 
   (c)   Connections subject to back pressure. Where a potable water connection is made to a line, fixture, tank, vat, pump or other equipment with a hazard of backflow or back-siphonage where the water connection is subject to back-pressure, and an air gap cannot be installed, the Utility Superintendent may require the use of an approved reduced pressure principal backflow preventer. A partial list of such connections is shown in the following table Partial List of Cross Connections Subject to Back Pressure.
 
Partial List of Cross Connection Subject to Back Pressure
Chemical lines
Pumps
Dock water outlets
Steam lines
Individual water supplies
Swimming pools
Industrial process water lines
Pressure tanks
Tanks and vats-bottom inlets
Hose bibs
 
   (d)   Barometric loop. Water connections where an actual or potential back-siphonage hazard exists may in lieu of devices specified above be provided with a barometric loop. Barometric loops shall precede the point of connection.
   (e)   Vacuum breakers. Atmospheric vacuum breakers shall be installed with the critical level at least six inches above the floor rim of the fixture they serve and on the discharge side of the last control valve to the fixture. No shutoff valve or faucet shall be installed beyond the atmospheric vacuum breaker. Pressure vacuum breakers shall be installed with the critical level at least 12 inches above the flood rim but may have control valves downstream from the vacuum breaker. For closed equipment or vessels such as pressure sterilizers the top of the vessel shall be considered the flood level rim and a check valve shall be installed on the discharge side of the pressure vacuum breaker. However, lawn sprinkler systems will be installed with a pressure vacuum breaker only.
(2010 Code, §15-233)