Cross-Connection and Backflow Prevention

Cross-connection and backflow are two issues that may cause the contamination or pollution of potable water, which is water that is fit for drinking, cooking and household uses.

  • Contamination is the introduction or presence of any foreign substance in a drinking water system that could or does make the water hazardous to human health. 
  • Pollution is the introduction or presence of any foreign substance in a drinking water system that could or does change the taste, odor or color of the water and weakens its usefulness but is not hazardous to human health.

Environmental Protection Agency Cross-Connection Control Manual

View the Environmental Protection Agency (EPA) Cross-Connection Control Manual for more information regarding:

  • Additional examples of assemblies and devices.
  • The principles of water pressure and backflow.
  • The types of problems that can and have been caused by cross-connections and backflow.
  1. Cross-Connection
  2. Backflow


Have you ever connected a garden sprayer to the end of a hose to fertilize your vegetables or flowers? Have you ever stuck the end of a garden hose into your car’s radiator or connected it to the heater hoses to flush the radiator? Or, have you ever placed the hose under the water’s surface in a swimming pool and left it on? Many of us do. However, doing any of these poses a risk of contaminating your home’s drinking water with chemicals that can cause serious health concerns if swallowed. 

A cross-connection is any existing or possible interconnection between a drinking water system and any other system that contains a substance of unknown or uncertain quality. It also is the link that can bring two systems together. The most common cross-connection is an outside hose faucet, typically called a hose bib or sillcock. Use these plumbing fixtures for connecting hoses that you use for various purposes such as watering your gardens, flowers and lawns.

Cross-Connection Control

Cross-connection control is the methods, practices and procedures used to prevent contamination or pollution of drinking water from backflow through cross connections. It ensures that your drinking water remains safe from bacteria, chemicals and other substances that may enter the water from unknown or improperly maintained sources because of abnormal pressure changes. A cross-connection control program is a written plan that:

  • Detects, monitors and manages cross-connections.
  • Implements the procedures and practices necessary to ensure safe drinking water to comply with government rules and regulations.