Backflow Prevention Assembly Types

A backflow prevention assembly is a device attached to the drinking water meter that keeps potentially contaminated water from the main water line. They are required by Florida Administrative Code and by local ordinance to protect the drinking water supply, keeping you healthy and safe. These assemblies are tested and repaired as needed to meet minimum requirements.

backflow prevention assembly type residential


Less than 1 inch

The majority of these assemblies are found in the drinking water meter box. They are either a brass, vertical cylinder attached to copper pipe (a dual check) or a horizontal brass cylinder attached directly to the meter (a T-10 combo).

Commercial/Small Fireline

backflow assembly prevention type commercial/small fireline

Less than 2 inches

These assemblies are installed either above ground or in a box. They are attached to the backside of the drinking water meter toward the building. These smaller Double Check Valve Assemblies (DCVA) or Reduced Pressure Zone Assemblies (RP) are painted blue to indicate that they carry drinking water. The body has two cylindrical areas that face up, small test cocks (ports) and a valve at each end. They are around 16 inches to 24 inches long.

Commercial or Multi-Family

backflow prevention assembly type DCVA and DCDA

Type DCVA/DCDA, greater than 4 inches

These larger assemblies are installed above ground and are located behind the meter. The Double Check Valve Assembly (DCVA) is used for a typical large business, condominium or high-rise building. The Double Check Detector Assembly (DCDA) is installed on a line that supplies water to the building’s fire suppression system, which includes the fire sprinklers or standpipes. They look like a larger version of the smaller assemblies with larger valves that have a stem and wheel-type shut-off valve. They range from 10 feet to 20 feet long, including the pipe on both ends. The DCVA is painted blue and the DCDA is usually painted red.

Commercial or Multi-Family

backflow assembly type commercial RP

Type RP, greater than 4 inches

This Reduced Pressure Zone Assembly is used on buildings like chemical manufacturing plants, large auto repair shops and schools with chemistry labs. It also is installed on the backside of the drinking water meter. It looks very similar to the DCVA except that is has an additional valve on the underside of the assembly. This valve is called a “relief valve.” It is also painted blue and is roughly the same length as the DCVA assembly.