Cross-Connection Control and Backflow Prevention

A cross-connection is any actual or potential connection between a drinking water system and a source that is not intended for drinking water use.

Common examples include:

• Irrigation systems
• Garden hoses
• Fire sprinkler systems
• Boilers and mechanical equipment
• Commercial or industrial water systems

When a cross-connection cannot be eliminated, a backflow prevention assembly may be required to help protect the drinking water supply.

Backflow is the unintended reversal of water flow through a plumbing system. Under certain conditions, changes in water pressure can cause water from a private plumbing system, irrigation system, or other connected source to flow back toward the public water system.

To help reduce the potential for non-potable water or other substances to enter the public water system, backflow prevention assemblies may be required where cross-connections cannot be eliminated. These mechanical devices are designed to allow water to flow in one direction while helping prevent reverse flow.

Requirements for backflow prevention assemblies vary based on a property's water use, plumbing configuration, and potential cross-connection hazards. Examples of properties that may require a backflow prevention assembly include:

• Properties with irrigation systems
• Fire protection systems
• Medical facilities
• Commercial and industrial properties
• Certain multi-family developments

Certain backflow prevention assemblies are required to be tested upon installation and annually by a Certified Backflow Prevention Assembly Tester.

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:

• Pre-Approved Product List Sheet Number 4.6
• The University of Southern California Foundation (USC) List of Approved Backflow Prevention Assemblies

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.

Specifications for backflow prevention assemblies

RPPA

• Reduced Pressure Zone Backflow Preventer for Water Service 3/4" thru 2"
• Reduced Pressure Zone Backflow Preventer for Water Service 4" thru 8"
• Reduced Pressure Zone Backflow Preventer for Water Service - Notes

DCDA/DCVA

• Typical Fire and Fire & Domestic Water Service Connections
• Double Detector Check Valve Assembly for Fire Line Service
• Double Detector Check Valve Assembly for Fire Line Service - Notes
• Double Detector Check Valve in Parallel

PVB

• Pressure Vacuum Breaker, Irrigation System Only
• Pressure Vacuum Breaker, Irrigation System - Notes

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:

• Completed Certified Tester Information form
• Copies of your:
  • Business/contract license, if applicable
  • Certificate of liability insurance
  • Backflow prevention assembly test kit(s) calibration certificate
  • Backflow prevention assembly tester certificate(s)
  • 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.

• Backflow prevention training offered by the University of Florida

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.

• Instructions on submitting test reports online

As an option to completing the report online, submit the completed form.

• Instructions on submitting test report form

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.