What is a backflow prevention device and which one is best to install?

Backflow prevention in a drinking water system is an in-line assembly that is used to keep undesirable water from entering the drinking water system during a backflow event. Your plumber will be able to assist you with the correct device for your system.  Generally, for residential water systems, a non-testable dual check valve assembly is adequate.

DEVICE TYPE TABLE BASED ON WATER USE AND DEGREE OF HAZARD