This page lists the various types of backflow prevention assemblies that are available. Some assemblies can be tested to ensure that they are working while others cannot. Typically, each assembly is designed to be used for a specific process hazard level application: low, medium or high hazard level.
Backflow preventers installed in residential irrigation systems are required to be tested tri-annually (once every three years). All other backflow preventers installed in or at a residential property must be tested annually.