Backflow Prevention

What is Backflow?

The Michigan Safe Drinking Water Act, 1976 P.A.399, defines backflow as water of questionable quality, wastes, or other contaminant entering a public water supply system due to reversal of flow. Check out the Blackflow Prevention Brochure (PDF) to learn more information.

Health Hazards

Backflow protection prevents undesirable water, sewage, bacteria, pathogens, or chemical solutions from entering your drinking (potable) water system.

Contamination of the public drinking water supply is a health hazard. A consumer is being subjected to potentially lethal water borne disease or illness.

Common Water Use Threats

Common water use that could pose a threat to drinking water include:
  • Chemically treated heating systems
  • Hose connections to chemical solutions
  • Hose connections to contaminated water such as in a laundry tub
  • Lawn irrigation and sprinkling systems
  • Non-approved ballcock assemblies in toilets
  • Private non-potable water supplies
  • Solar heating systems
  • Swimming pools
  • Water operated sump drain devices
  • Water softeners

Backflow Prevention Law

The Michigan's Safe Drinking Water Act, P.A. 399, 1976 (As Amended), Michigan Plumbing Code 2009, and local government Cross Connection Control Ordinances that require backflow prevention device installation and regular testing. It is the property owner's responsibility to ensure that backflow prevention devices are properly installed, and tested in compliance with Act 399 of 1976, as Amended.

Backflow Prevention Device Testing


Beginning January 1, 2018 test results of backflow prevention assemblies are valid only if testing was performed by individuals holding an active ASSE 5110 certification.  

A listing of all ASSE approved devices may be found at  Michigan also allows devices approved by Canadian Standards Association (CSA).  The appropriate CSA standards for each type of backflow preventer can be found in the latest edition of the Michigan Plumbing code.

All testable backflow devices are to be tested upon installation, and tested thereafter at a frequency to be determined by the DPW. Testers certified by the State of Michigan shall test and install backflow prevention devices. Testing varies by device type and typically takes 10 to 30 minutes. The water supply to the backflow preventer is turned off during testing.

Backflow & Cross Connection Resources