Minimum test frequency for back flow prevention assemblies.
At least yearly
More frequent than annual testing of back flow assemblies may be indicated under these conditions.
- Extremely high hazard condition- History of annual test failure
This should be required if a facility has an auxiliary water system that is or could be connected to the public water system.
An approved back flow prevention assembly installed at the water service to the facility
This method of cross connection control is typically required on the service to a sewage treatment plant.
Approved air gap separation
Approved cross connection control methods when chemicals or other high hazard materials may enter the potable water system.
- Reduced back flow assembly (RPBA)- Air gap (AG)
Air gap.
Vertical separation between a potable water supply pipe and the flood rim of a receiving vessel at least 2x the supply pipe diameter, but never less than one inch.
Facilities that may have high hazard cross connections.
- Hospital- Mortuary- Chemical plant- Metal plating plant- Sewage treatment plant
Contamination.
Introduction of materials into water such as disease producing micro-organisms or toxic substances that pose a health risk
Pollution.
Introduction of materials into water that are objectionable, and will render the water unfit for its intended use
Cross connection.
Any actual or potential physical connection between a potable water line and any pipe, vessel, or machine containing a non-potable fluid so that it is possible for the non-potable fluid to enter the potable line by backflow
Hydraulic conditions that can cause backflow.
- Back pressure- Back siphonage
Key installation requirement for reduced pressure backflow assemblies.
Insure that relief valve cannot be submerged
Hazard compatible with double check valve assembly.
Low hazard only
Selection of a backflow prevention assembly is based on this.
- Degree of hazard- Hydraulic condition (back pressure or back siphonage)
Cross connection control where there are toxic chemicals such as pesticides or fertilizers require this type of protection.
RPBA or air gap protection
Use of these types of chemicals may pose a backflow contamination threat.
- Pesticides- Fertilizers- Boiler and heat exchanger chemicals- Antifreeze chemicals- Cleaning agents such as soaps and detergents
These backflow prevention devices should only be used in a back siphonage condition, never back pressure.
Vacum breakers:
- Atmospheric vacum breaker
- Pressure vacum breaker
This backflow assembly includes a spring loaded air inlet valve and a check valve.
Pressure vacuum breaker
These backflow prevention methods protect against back pressure, and back siphonage.
- Air gap
- Reduced pressure backflow assembly
- Double check valve assembly
An improperly operated fire truck pumper can create this distribution system hazard.
Back siphonage due to low pressure in the main
Implement a cross connection control program.
- Local ordinance that empowers a water supplier to implement a program
- Water use inspection of facilities supplied by the water system
- Installation of backflow devices at facilities where the cross connection hazards are identified
- Backflow assembly testing program, to provide annual test
This backflow assembly includes two independently operating check valves and a differential pressure relief valve.
Reduced pressure backflow assembly (RPBA)
Reasons a relief port must never be plugged or extended.
- It would interfere with the operation of the relief valve.
- It would interfere with the testing of the backflow assembly.
