Potable water:  water that is considered safe to drink.

Non-potable water:  water that is NOT considered safe to drink, and may also include gasoline, pesticides and other chemicals.

Cross connection occurs when potable water is mixed with a non-potable substance.

The mixing may occur because the pressure of the non-potable substance overrides the pressure of your potable water: OR because something happened that drew non-potable substances back into the water system. 

Cross connection can be controlled with backflow devices. 

The most common backflow device is a double check valve.  This device, when hooked to your service line stops water from flowing back into the water main. You are required to have this device to keep contaminated water from flowing back into your house if you use domestic water to supply an underground lawn irrigation line.

If you are using a pesticide and putting a hose into the same container with the pesticide you must use a backflow device or keep the hose more than 6 inches above the container.

Another backflow device is a pressure regulating valve.  This device not only stops water from back flowing, it also dumps the contaminated water on the ground. This is generally used at commercial locations due to the greater risk of non-potable substances back flowing into the domestic water system.  

The Department of Health has information about the use of backflow devices and the information sheets we have included in our billings are designed to inform you about cross connection.