Backflow Prevention & Avoiding Cross-Connections
A cross connection is an arrangement of piping or more commonly a garden hose between the potable water or drinking water supply and any other substances. Examples of a cross connection include:
- A garden hose placed into a spa, swimming pool, or pond.
- Use of a device to apply pesticides or fertilizer to a lawn via a garden hose.
- A heat recovery unit or heat exchange unit.
- Attaching a well to a dwelling that is serviced by a potable water system.
- Use of a hose to unclog a drain or sewer system.
Anyone observing a Cross Connection or a potential Cross-Connection should inform their local office.
Fixtures That Have a Potential for Cross Connection
Fixtures that have a potential for cross connection include
- Agriculture Mixing Tanks
- Auxiliary Water Supply
- Garden Hose
- Ornamental Ponds
- Photographic Developers
- Solar Energy Systems
- Swimming Pools
- Toilet Flush Valves
- Water Softeners
- Watering Troughs
Causes of Backflow
- Line repair or break that is lower than the point of service. This allows negative pressure to be created by water flowing to a lower point in the distribution system.
- Undersized piping under high withdrawal rates can create a pressure differential allowing contaminates to enter the distribution system.
- Lower water main pressure due to high withdrawal rates.
- Reduced supply main pressure on suction side of a booster pump.
- Booster pumps without backflow protection devices.
- Potable water connections to boilers and other pressure systems without backflow prevention devices.
- Connections with other systems that may have higher pressures.
- Storage tanks or plumbing systems elevated enough to create sufficient head to allow backflow condition should distribution pressure drop.
Cross Connections: A physical arrangement between a potable water system and any other fluid.
Back Pressure: A condition in which the owner’s system pressure is greater than the supplier’s system pressure.
Back Siphonage: The flow of substances into the distribution system caused by a sudden reduction of pressure in the potable water system.
Contaminate: Any substance that will impair the quality of potable water creating a public health hazard.
Potable Water: Any water that is safe for human consumption according to recognized standards.
Air Gap: A physical separation between the free flowing discharge end of the potable system and any other systems.
Reduced Pressure Principle Device: An assembly of two independent operating check valves with an automatic differential relief valve.
Double Checkvalve Assembly: An assembly of two independently operating spring loaded check valves.
Pressure Type Vacuum Breaker: Contains one or two independently operated check valves.
Auxiliary Supply: Any other water supply available on the premises.