The City of Pascagoula has a Cross-Connection Control Policy as required by the Safe Drinking Water Act. Cross connections usually occur by accident. Suppose, for instance, that you are washing your dog. Suddenly, the dog runs off chasing fire engines down the street. In your haste, you drop the running hose down into the bucket of soapy wash water thus creating a cross connection. As the firefighters attack the blaze, the fire trucks attach a suction to the hydrant creating a vacuum within the water main. The water in the bucket could then be sucked into the water main - soap, fleas and all! You, and your neighbors have just experienced backflow.

In order to prevent this possibility from occurring, backflow preventers are part of the City's Cross-Connection Control Policy. For further information about this policy and its implementation, you may call 938-6618 to set up an appointment.

What is a backflow preventer?  The basic means of preventing backflow is an air gap, which either eliminates a cross-connection or provides a barrier to backflow.
The basic mechanism for preventing for  backflow is a mechanical backflow preventer, which provides a physical barrier to backflow.  The principal types of mechanical backflow preventers are the reduced-pressure principle assembly, the pressure vacuum breaker assembly and the double check valve assembly.  A secondary type of mechanical backflow preventer is the residential dual check valve.

What is a reduced-pressure principle assembly (RP)?   An RP is a mechanical backflow preventer that consists of two independently acting, spring-loaded check valves with an hydraulically operating, mechanically independent, spring-loaded pressure differential relief valve between the check valves and below the first check valve.  It includes shutoff valves at each end of the assembly and is equipped with test cocks.
An RP is effective against backpressure backflow and backsiphonage and may be used to isolate health and nonhealth hazards.

What is a pressure vacuum breaker assembly (PVB)?   A PVB is a mechanical backflow preventer that consists of an independently acting, spring-loaded check valve and an independently acting, spring-loaded air inlet valve on the discharge side of the check valve.  It includes shutoff valves at each end of the assembly and is equipped with test cocks.
A PVB may be used to isolate health or nonhealth hazards but is effective against backsiphonage only.

What is a double check valve assembly (DC) ?   A DC is a mechanical backflow preventer that consists of two independently acting, spring-loaded check valves.  It includes shutoff valves at each end of the assembly and is equipped with test cocks.
A DC is effective against backpressure backflow and backsiphonage but should be used to isolate only nonhealth hazards.

What is a residential dual check valve (rdc)?   An rdc is similar to a DC in that it is a mechanical backflow preventer consisting of two independently acing, spring-loaded check valves.  However, it usually does not include shutoff valves, may or may not be equipped with test cocks or ports, and is generally less reliable than a DC.  An rdc is effective against backpressure backflow and backsiphonage, but should only be used in nonhealth hazards and is intended for use ONLY in connections to single-family homes.

Why do backflow preventers have to be tested periodically?  Mechanical backflow preventers have internal seals, springs and moving parts that are subject to fouling, wear or fatigue.  Also, mechanical backflow preventers and air gaps can be bypassed.  Therefore, all backflow preventers have to be tested periodically to ensure that they are functioning properly.  A visual check of air gaps is sufficient, but mechanical backflow preventers have to be tested with properly calibrated gauge equipment.

Where can I get more information about cross-connection control?  One excellent reference manual is the second (1990) edition of the American Water Works Association's (AWWA's) Manual M14, Recommended Practice for Backflow Prevention and Cross-Connection Control, which is available from the AWWA Bookstore: 6666 West Quincy Avenue; Denver, Colorado 80235; or call 1-800-926-7337.  Their web address is http://www.awwa.org.  Another excellent reference manual is the ninth (1993) edition of the University of Southern California's Manual of Cross-Connection Control, which is available from the Foundation for Cross-Connection Control and Hydraulic Research: University of Southern California; KAP-200 University Park MC-2531; Los Angeles, CA 90089-2531; or call 213-740-2032. Their web address is http://www.usc.edu/dept/fccchr