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Refer to the Backflow Prevention section in the CBU Design Standards Guidelines Manual for all requirements to be included on your plumbing plan submittal (domestic water / fireline / irrigation).  Also refer to Standard Details listed below to see which ones might be applicable for your project.  Click here for more info.



Backflow Prevention:  A reduced pressure principle assembly is recommended on all commercial customer service lines and multifamily service lines.  An approved backflow prevention assembly is required on all customer service lines if the building will house a designated cross connection hazard as specified by 327 IAC 8-10-4 or as determined by CBU.  All devices must be tested and submitted to CBU by an Indiana Registered Cross Connection Control Device Inspector upon installation and at intervals not to exceed 12 months. 


Plan submittals must include the location and make and model number of backflow prevention device.  For more information about backflow prevention requirements or to seek approval for a proposed device, please contact the Environmental Program Coordinator at (812) 349-3948.



  • SYSTEMS WITH CHEMICAL ADDITIVES:  Per Indiana Plumbing Code, a reduced pressure zone (RPZ) backflow assembly must be installed with fire systems containing chemical additives.
  • LOCATION OF THE FIRE RISER:  CBU requires a single detector check (SDC) valve to be installed on the fire line if the fire riser is 50' or more from the connection to the main. This water quality device shall be installed in a manhole located closer to the main. A second reduced pressure zone (RPZ) assembly shall be installed on the domestic service line.
  • DEVICE OPTIONS:  A different backflow device may be considered if the potential sources of cross connection and the techniques to prevent contamination from those sources are clearly outlined and submitted to CBU. 
  • DEVICE DETAILS:  Please submit the make, model number, and location of all backflow prevention devices to the Environmental Program Coordinator at (812)349-3948 or by email at:
  • TESTING REQUIREMENTS:  All devices must be tested and submitted to CBU (via the TrackMyBackflow website) by an Indiana Registered Cross Connection Control Device Inspector upon installation and at intervals not to exceed 12 months.


Additional information about our Backflow Prevention Program, standard details, approved devices, installation / inspection requirements, device testing requirements, and submission of the testing reports is also available on our website.  For more Program details, Informational Brochures, etc, visit the Backflow Program section on the previous page, or contact our Environmental Program Coordinator at 812-349-3948, or by email:

backflow diagram







  • There are multiple types of Backflow Prevention Devices, the four most common being:

    • Air Gap
    • Pressure Vacuum Breaker (PVB)
    • Reduced Pressure Zone (RPZ)
    • Double Check Assembly (DCA) / Double Check Detector Assembly (DCDA) 




  • What is the difference between a double check valve backflow preventer and a reduced pressure zone backflow preventer (RPZ)?

    • RPZ backflow preventers include two check valves like a double check backflow preventer, but they also have an intermediate relief valve that opens to atmosphere if both check valves should fail.


  • Can an RPZ be installed vertically?

    • Backflow preventers must be installed in the installation orientation for which they were designed and approved (vertical, horizontal etc.).

    • There are backflow preventers that can be installed horizontally, vertically (up or down) and other orientations that can make an installation easier.


  • Examples of Service Types where Backflow Prevention is Required:

    • Firelines
    • Domestic Services of Multi-family Residences (Master-metered apartments, dormitories, etc)
    • Domestic Services of Commercial buildings where there is a potential cross-connection hazard
    • Domestic Service of Restaurants where there is a potential cross-connection hazard
    • Irrigation System Service Lines
    • Water Filling Stations / Water Hauling Trucks
    • Hydrant Meters used for construction purposes, filling water tanks, pools, new landscaping/sod, etc.