A cross-connection is an actual or potential link between the potable water supply (water safe for human consumption) and a non-potable source (any other type of liquid, gas or substance not fit for consumption that can affect water quality). This can cause our drinking water to become contaminated or polluted.
A cross-connection can be avoided by eliminating the link between the two sources. If the link cannot be removed, then the potable water supply must be protected through the use of a backflow prevention assembly.
The most common cross-connection is a typical garden hose, which is left submerged in a volume of water or other fluid (i.e. a garden hose left in a bucket of soapy water). Other cross-connections include kitchen sprayers in a sink filled with dirty water, irrigation systems, boilers and other appliances supplied by water.
Miami-Dade County’s Cross-Connection Control Unit was established in order to implement the rules of the Florida Administrative Code, which requires public water systems to establish cross-connection control programs to detect, prevent and eliminate cross-connections that may create an imminent and substantial danger to the public health.
Backflow is the undesired reversal of flow of water and/or other substance into the potable water supply, via a cross-connection, due to a change in pressure caused by either backpressure or backsiphonage.
Backpressure is a type of backflow condition that exists when the pressure in the downstream side of the customer’s piping system becomes elevated greater than the supply pressure at the potable water system. Backsiphonage is a type of backflow condition that exists when the pressure in the potable water supply system becomes lower than atmospheric pressure (14.7 psi).
The potable water supply can be protected from backflow by eliminating all cross-connections or through the use of the proper backflow prevention assembly.
A backflow prevention assembly or backflow preventer is a mechanical valve arrangement designed to prevent the "backflow" or reversal of flow of water, once it has passed through the valve. There are different types of backflow preventers for different uses and different degrees of hazard.
Because the backflow preventer is a mechanical device with springs, moving parts and rubber seating surfaces, which wear over time, it must be tested upon installation and every year to ensure that the assembly is working properly.
Miami-Dade County Code requires backflow prevention assemblies to be installed on certain services depending on the degree of hazard, the type of service (i.e. fire suppression system, irrigation system, domestic water system) and the use of the facility. For a list of backflow preventers approved to be used in WASD facilities refer to:
The different types of backflow prevention assemblies are the Reduced Pressure Principle Assembly (RPPA), the Double Check Valve Assembly (DCVA), the Double Check Detector Assembly (DCDA) and the Pressure Vacuum Breaker (PVB).
The RPPA is typically installed at the domestic water service connection, the DCVA/DCDA are typically installed at the water service connection that supplies fire suppression systems and the PVB is typically installed at the water service connection that supplies lawn irrigation systems.
A certified tester must complete a 40-hour training course in backflow prevention assembly testing and pass a proficiency test. A licensed plumber or contractor may install a backflow prevention assembly.
To join the Water and Sewer Department’s list of companies with certified testers, mail or fax the following documents:
Contractor license of the backflow prevention assembly testers, of applicable
However, there is a permit fee associated with having a Backflow Prevention Assembly installed. The fees are determined by the Building Department of the city in which you are having the assembly installed.
Certified testers are not endorsed by the Water and Sewer Department. In addition, many plumbing, fire sprinkler, lawn irrigation and backflow preventer testing companies are listed in local telephone directories.
Companies (not the Water and Sewer Department or Miami-Dade County) determine the cost to have backflow prevention assemblies tested and installed. A licensed plumber or contractor may install a backflow prevention assembly.
Test reports can be submitted online with information provided by the Water and Sewer Department.
Every tester has a unique user name and password – both of which are not case sensitive.
If you have an assembly at your home or business, follow these guidelines to prevent theft:
Build a barrier wall up to six inches above the highest point of the body of the assembly, so that the stems of the shutoff valves are visible from outside the wall structure
Create a recessed covered space which is part of the building envelope
Purchase a manufactured cover for small diameter assemblies up to two inches
If your assembly has been tampered with or stolen, or if you see any suspicious activity in your area, call the police immediately.
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