Backflow Prevention & Avoiding Cross-Connections
What is it?
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:
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.
Causes of Backflow:
1. 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.
2. Undersized piping under high withdrawal rates can create a pressure differential allowing contaminates to enter the distribution system.
3. Lower water main pressure due to high withdrawal rates.
4. Reduced supply main pressure on suction side of a booster pump.
1. Booster pumps without backflow protection devices.
2. Potable water connections to boilers and other pressure systems without backflow prevention devices.
3. Connections with other systems that may have higher pressures.
4. Storage tanks or plumbing systems elevated enough to create sufficient head to allow backflow condition should distribution pressure drop.
Anyone observing a Cross Connection or a potential Cross-Connection should inform their local office.
Fixtures that have a potential for cross connection:
|Garden Hose||Toilet Flush Valves||Auxiliary Water Supply|
|Solar Energy Systems||Sprinklers||Water Softeners|
|Watering Troughs||Agriculture Mixing Tanks||Swimming Pools|
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 (RPZ): An assembly of two independent operating check valves with an automatic differential relief valve.
DOUBLE CHECKVALVE ASSEMBLY (DCVA): An assembly of two independently operating spring loaded check valves.
PRESSURE TYPE VACUUM BREAKER (PVB): Contains one or two independently operated check valves.
AUXILIARY SUPPLY: Any other water supply available on the premises.