A cross-connection is defined as any real or potential connection that could contaminate or pollute the public water system or your drinking water. Backflow is the reversal of the direction of the water flow through these cross connections that causes the contamination of pollution of the water supply.  Typically, this occurs as backsiphonage by a loss in water supply pressure, often due to the opening of a fire hydrant nearby, abnormally heavy water uses or a water main break. Although not as common for residential properties, backflow can be also be caused by backpressure.  Backpressure is when the demand water pressure becomes greater than the supply pressure and is caused by a booster pump or heating system. 

With lawn irrigation systems, water can accumulate around the sprinkler heads. A loss in water pressure would cause that pooled water to be siphoned back through the pipes and into your plumbing system, even potentially to the main water supply, carrying with it any fertilizer chemicals, pesticides, animal waste and/or parasites on the ground (YUCK! 😝). 

To prevent this, all lawn irrigation systems should be protected by an approved backflow prevention assembly, which must be tested annually.  The level of protection required for your lawn irrigation system is based on whether it is a water-only system or if there is a chemical additive system.  

Please consult your sprinkler contractor or plumber to make sure your system is protected and compliant with federal, state, and/or local code.