Click here to skip to main content.
scenic picture from Washington state
SUBJECTS › PUBLIC WORKS › Cross-Connection and Backflow Prevention
Updated 05/09

Cross-Connection and Backflow Prevention

Contents

Introduction

A cross connection is defined as any actual or potential physical connection between a public water system or the consumer's water system and any source of non-potable liquid, solid, or gas that could contaminate the potable water supply by backflow. Cross connections exist in all plumbing systems. Cross connections may also exist in the purveyor’s water system facilities.

There are numerous well-documented cases where drinking water has been contaminated via unprotected cross connections. These cases have caused illness, injury, and in some cases, death, to consumers served by the system.

The task of eliminating all cross connections is enormous. However, all purveyors can implement CCC programs that reasonably reduce the risk of contamination to their systems. For a drinking water (potable water) supply to become contaminated via a cross connection, three things need to happen simultaneously:

  • The potable water supply piping must be unprotected (or improperly protected) from a cross connection; 
  • A physical cross connection must be made between the potable water supply piping and a contaminant source; and
  • Backflow conditions must occur.

    • Backflow is the flow of water (or other solid, liquid, or gas from any source) back into the potable water supply. Backflow may be due to either:

  • Back siphonage; or
  • Backpressure.

    • The Washington State Department of Health (DOH), through its Office of Drinking Water, is charged with enforcing regulations for protecting potable drinking water systems and has significant resources on its web pages and links to other resources

    Washington State Health Regulations

    Washington Administrative Code Provisions - Cross Connection and Back Flow Prevention

    Ordinance Provisions and Programs

    As the Department of Health regulations must be followed, most agencies simply adopt the DOH standards

    Reference Sources