Only two types of backflow preventers are acceptable under the Utilities Kingston Cross Connection Control Program (CCCP) for premises isolation:
- Reduced Pressure Principle (RP)
- Double Check Valve Assembly (DCVA)
Reduced pressure
- two independently acting check valves separated by a reduced pressure zone
- installed as a unit between two shut-off valves
- each check valve is fitted with a test cock for periodic testing
- can be used for health hazards (i.e., toxic material) and severely hazardous connections (i.e., hospitals, morgues, medical/dental facilities, industrial or chemical plants)
Double check valve assembly
- two internally loaded check valves, force-loaded or internally weighted
- if one check valve fails to close the other will prevent backflow
- each check valve is fitted with a test cock for periodic testing
- can be used for all non-health hazards (non-toxic) connections (i.e., fire sprinkler, irrigation systems)
The following types of backflow prevention devices are typically used for zone or fixture isolation. They are not suitable for premises isolation because they are not testable or because they have limited protection levels (or both). Since the Utilities Kingston’s Cross Connection Control Program is for premises isolation only, these BPDs are not acceptable under the program.
Atmospheric Vacuum Breaker (AVB)
- one of the simplest and least expensive backflow prevention devices
- available in half-inch to three-inch pipe sizes
- must be installed vertically and be at least six inches higher than the downstream piping for proper operation
- device cannot be used under constant pressure and cannot be tested
- can only be used to prevent back siphonage, not back pressure
- can be used for irrigation systems, commercial dishwasher and laundry equipment, chemical tanks, and laboratory sinks
Pressure Vacuum Breaker (PVBA)
- an outgrowth of the atmospheric vacuum breaker
- can only be used to prevent back siphonage, not back pressure
- can be used under constant pressure and can be tested
Hose Connection Vacuum Breaker (HCVB)
- a spring-loaded check valve that seals against an atmospheric outlet when the water supply is turned on
- the HCVB vents to atmosphere when it is turned off, protecting against back siphonage conditions
Dual Check Value (DuC)
- two independently acting, spring loaded check valves
- usually does not have shutoff valves and may or may not be equipped with test cocks
- should only be used to isolate non-health hazards and is intended for single family homes
