A cross-connection is defined as any real or potential connection that could contaminate or pollute the public water system or your drinking water. Cross-connections are caused by backflow. Backflow occurs when a loss in water pressure, often due to the opening of a fire hydrant nearby, abnormally heavy water uses or a water main break, which causes the water in your pipes to flow in the opposite direction. This could allow contaminated or polluted water to flow back into your drinking water. This is referred to as backsiphonage. Backflow can also be caused by what is called backpressure. This is less common for residential properties but can occur if using a booster/auxiliary pump for an irrigation or fire protection system.
With a lawn irrigation system, water can accumulate by the sprinkler heads. A loss in water pressure would cause that water to be sucked back through the pipes and into your plumbing system, carrying with it any fertilizer chemicals, pesticides, animal waste and/or parasites on the ground. All lawn irrigation systems should be protected by an approved backflow assembly, which must be tested annually.
Please consult your sprinkler contractor or plumber to make sure your system is protected and up to federal, state, and/or local code.