Protecting Our Drinking Water: Understanding Cross-Connection Control and Backflow Prevention

Ensuring the safety of our community’s drinking water starts with preventing contamination at the source. One important way we do this is through cross-connection control and backflow prevention. A cross-connection is any actual or potential link between a safe drinking water supply and a source of contamination—like a garden hose submerged in a swimming pool or connected to a pesticide sprayer. If water pressure drops (from a main break or heavy usage), this can cause backflow, allowing non-potable water to flow back into the clean water system. To prevent this, backflow prevention devices are installed at key points in the water system. These devices protect our health by ensuring water only flows in one direction—toward your tap. 

How Contamination Can Occur

Backflow is the reverse flow of water from a non-potable water source into the drinking water system, potentially contaminating your drinking water. Backflows can occur at unprotected cross-connections due to pressure differences.

Backflow can occur in two ways:

• Backpressure: When the pressure in a non-potable water source (such as a boiler) is greater than the pressure in the drinking water system, contaminants from the non-potable source can be pushed into your drinking water. Buildings four or more stories high with booster pumps may generate backpressure.
  
• Backsiphonage: When there is a sudden drop in the drinking water system pressure, such as during firefighting or a water main break, a vacuum or siphoning effect can draw non-potable water and any contaminants present into your drinking water.

Backpresure

Backsiphonage

Requirements for Property Owners

As a property owner, you are responsible for cross-connection control on your side of the water meter. To prevent contaminants from entering your drinking water, air gaps or approved backflow prevention assemblies may be required to protect against backflow at cross-connections. 

• Air gaps are physical vertical separations between water supply outlets (such as faucets) and the highest fill levels of the receiving containers. Air gaps must be inspected annually by approved testers or specialists.
• Backflow prevention assemblies stop the reverse flow of water into the drinking water system when pressure changes occur. After proper installation, these assemblies must be inspected and tested annually by approved testers.

 Failure to comply with these requirements could result in fines or discontinuation of your water service until proper cross-connection control is in place.

 Your attention to these safety measures protects your property’s water quality, keeping drinking water safe for you and the community.