Water Protection Program fact sheet
Division of Environmental Quality Director: Kyra Moore

Backflow prevention for all community water systems is defined in state regulation 10 CSR 60-11.010. The rule establishes requirements for protection of public water systems from introduction of contaminants by backflow. The responsibilities of the customer, water supplier and the Missouri Department of Natural Resources are set forth in the rule. Potential backflow hazards are listed and classified. Backflow prevention assembly testing and inspection requirements are explained. The water supplier is required to notify the department within 48 hours of a backflow incident that caused contamination in the public water system.

Backflow is prevented by the installation of an air gap separation, a reduced pressure principle assembly or a double-check valve assembly on the customer service line. The department requires backflow prevention assemblies installed at community water systems be approved by the Foundation for Cross-Connection Control and Hydraulic Research at the University of Southern California or the American Society of Sanitary Engineering (ASSE). Information about approved assemblies is available on the department’s Backflow Prevention webpage. All air gaps, reduced pressure principle assemblies and double-check valve assemblies shall be inspected when installed and at least annually thereafter by a certified backflow prevention assembly tester.

Backflow prevention assembly test certification requirements are set forth in 10 CSR 60-11.030. Backflow prevention assembly tester certifications are valid for three years. Each candidate for certification as a backflow prevention assembly tester must successfully pass a written and hands-on performance examination provided by either the American Backflow Prevention Association (ABPA) or ASSE and become certified by one of those two organizations. The department prepares and provides an annual schedule of dates and locations of backflow prevention assembly tester certification upon request.

The written examinations given by ABPA and ASSE contain about 100 questions covering the basic required knowledge for application and testing of backflow prevention assemblies. The examination for testers certified in Missouri must include questions specific to Missouri backflow prevention rules. Both the written and performance examinations are proctored by a third party. Course instructors may not test their own students.

The backflow prevention regulations are available on the department’s Backflow Prevention webpage.


Nothing in this document may be used to implement any enforcement action or levy any penalty unless promulgated by rule under chapter 536 or authorized by statute.

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