(a) Double check valve assemblies may be utilized at premises where a substance is handled that would be objectionable but not hazardous to health if introduced into the potable water system.
(b) DCs shall be sized to provide an adequate supply of water and pressure for the premises being served. Flow characteristics are not standard. Consult manufacturer’s specifications for specific performance data.
(c) Premises where interruption of water supply is critical shall be provided with two assemblies installed in parallel. They shall be sized in such a manner that either assembly will provide the minimum water requirements while the two together will provide the maximum flow required.
(d) Bypass lines are prohibited. Pipe fittings which could be used for connecting a bypass line shall not be installed.
(e) (1) The assembly shall be readily accessible with adequate room for testing and maintenance. DCs may be installed below grade, providing all test cocks are fitted with brass pipe plugs. All vaults shall be well drained, constructed of suitable materials, and sized to allow for the minimum clearances established below.
(2) Assemblies two inches and smaller shall have at least a three-inch clearance below and on both sides of the assembly, and if located in a vault, the bottom of the assembly shall be not more than 24 inches below grade. All assemblies larger than two inches shall have a minimum clearance of 12 inches on the back side, 24 inches on the test cock side and 12 inches below the assembly. Headroom of six feet is required in vaults without a fully removable top. A minimum access opening of 24 inches square is required on all vault lids.
(3) Assemblies installed more than five feet above floor level shall have a suitable platform for use by testing or maintenance personnel.
(f) Vertical installations are allowed on sizes up to and including four inches that meet the following requirements:
(1) Internally spring-loaded check valves;
(2) Flow is upward through assembly;
(3) Manufacturer states their assembly can be used in a vertical position; and
(4) Approved by director.
(g) The assembly shall be protected from freezing and other severe weather conditions.
(h) Lines shall be thoroughly flushed prior to installation. A strainer with blowout tapping may be required ahead of the assembly.
(i) The property owner assumes all responsibility for foundation or basement wall penetration, leaks and damage. The owner shall also see that the vault is kept reasonably free of silt and debris.
(j) All DCs shall be tested in accordance with this division. Tests are the responsibility of the assembly owner. The owner shall notify the director upon installation of any backflow prevention assembly.
(k) Variances from these specifications will be evaluated on a case-by-case basis. No deviations shall be permitted without prior written approval of the director.
Double Check Valve Large Assembly
Notes:
(1) Large assemblies are those that are 2-1/2 inches and larger.
(2) Installations require the use of brass plugs in all test ports.
(3) The installation on the supply line (ahead of assembly) of a strainer with tapping blowout may be required. See standard detail no. 12.5-556.3.
Double Check Valve Small Assembly
Notes:
(1) Adequate space must be allowed for testing and maintenance.
(2) Area around assembly must drain well.
(3) Test cocks must be equipped with brass pipe plugs.
(4) “Y” pattern assemblies must be installed so that the test cocks are pointed up. (See drawing above).
(5) Thoroughly flush the lines prior to installation of the assembly.
(6) Strainers may be required. See standard detail no. 12.5-556.3.
Strainers
One of the most common causes of backflow prevention assembly failure is the accumulation of sand, scale or debris trapped in the assembly. This debris can cause the assembly to fail its required testing and can contribute to a shorter working life span of the assembly.
(Ord. 12274, § 1, passed 11-28-1995)