PROTECTING THE POTABLE WATER SUPPLY

Who Needs a backflow device?

Residents are required to install a backflow prevention device on the potable water meter if there is a water well or swimming pool onsite or when reclaimed water is used for irrigation.
The City specifies the type of device needed according to the relative contamination hazard.

What is cross-connection?
A cross-connection occurs in a plumbing system when the potable water supply is connected to a non-potable (not fit to drink) source. For the residential customer, sources of non-potable water include swimming pools and irrigation systems fed from a well or reclaimed water. Cross-connection of an unprotected water supply can result in contamination of the water supply.

The water distribution system is designed for the water to flow from the water treatment plant to the consumer. but wherever a cross-connection exists, and the potable water supply is not protected by a Backflow Prevention Device, backflow may occur due to either backsiphonage or backpressure.

Backsiphonage occurs when the pressure in the distribution system drops, siphoning water from the consumer's plumbing system into the distribution system. The pressure drop could be caused by a line break or high water withdrawal such as with fire fighting. A cross-connection that may result in backsiphonage would be a garden hose left in a swimming pool or a below the rim water inlet to a tank containing toxic chemicals.

Backpressure may cause backflow when a potable water system is connected to another system operating at a higher pressure. When an unprotected water line is attached to the higher pressure system, its contents can be "pumped" back into the potable water system. Cross-connections that may result in backflow due to backpressure include, booster pumps designed without backflow prevention devices and potable water connections to irrigation and other pressure systems

Where are cross-connections found?
Whenever a plumbing system is modified there is potential to create cross-connections. This is especially true when the property is served by an auxiliary water source such as reclaimed water or a well in addition to the potable water supply. Sources of cross-connection include:
1. Laboratory equipment
2. Irrigation sprinkler systems
3. Recirculating water systems
4. Swimming pools
5. Solar heating systems
6. Fire sprinkler systems
7. Hose connections