9-2-4: USE OF BACKFLOW PREVENTION DEVICES:
   A.   Installation Requirements; Certain Circumstances: Backflow prevention devices shall be installed, if possible, within the confines of the affected building in a readily accessible location with adequate clearances for maintenance and testing. If the preceding installation is not possible, the device shall be installed in an accessible, aboveground, locked, heated, enclosure adjacent to the structure. The structure shall be situated above seasonal high groundwater, shall contain a floor drain, shall provide adequate room for testing and maintenance and shall protect the device against freezing. Backflow prevention devices shall be installed under any circumstances included in, but not limited to, the following:
      1.   Premises housing an auxiliary water supply that has not been approved by the city for its quality and protection.
      2.   Premises having intricate plumbing arrangements which make it difficult to ascertain whether or not cross connections exist.
      3.   Premises where entry is restricted so that inspections for cross connections could not be made during reasonable hours, at sufficiently short notice to assure that cross connections do not exist.
      4.   Premises where any substance handled under pressure could enter into the water supply system. This shall include the handling of process and cooling waters.
      5.   Premises having a repeated history of cross connections being created or recreated.
   B.   Types Of Facilities Requiring Devices:
      1.   The following types of facilities shall fall into one of the above categories where a backflow prevention device is required to protect the water supply system, unless the city and the state department of environmental quality determine that no hazard exists:
         a.   Sewage treatment plants.
         b.   Laboratories.
         c.   Food processing plants.
         d.   Chemical or other industrial plants.
         e.   Hospitals, mortuaries, clinics.
         f.   Agricultural chemical storage, formulation and distribution facilities.
         g.   Petroleum processing or storage plants.
         h.   Car washes.
         i.   Other facilities specified by the city and the state department of environmental quality.
      2.   Certain public facilities present potential sources of cross connections. All of the following facilities and any others the city specify shall be required to install backflow prevention devices as required by the city:
         a.   Schools.
         b.   Movie theaters.
         c.   Recreation and sports grounds.
         d.   Restaurants.
         e.   Stores (wholesale or retail).
   C.   Types Of Devices For Use: The type of backflow prevention device required for a particular situation shall be commensurate with the degree of hazard presented. The following guides shall be used:
      1.   Where the water supply system could be contaminated as a result of cross connection, an air gap separation or a reduced pressure backflow prevention device shall be installed.
      2.   Where cross connection could result in pollution of the water supply system, either of the above devices or a double check valve assembly shall be used.
      3.   Back siphonage, such as from irrigation sprinkler systems, may be prevented by the use of either atmospheric vacuum breakers or pressure vacuum breakers, as directed by the city and the state department of environmental quality.
   D.   Stagnant Water; Double Check Valve Assembly: Facilities having plumbing arrangements connected to the water supply system, where the water remains stagnant for prolonged periods of time, shall be required to install a double check valve assembly. (2003 Code § 9-03-04)