At HPS Plumbing Services, we provide residents throughout San Diego with backflow prevention testing and education. The purpose of this device is to prevent your water supply from being contaminated by dirty water. If you have a backflow prevention device installed on your property, you are likely aware that you are required to have it tested each year. Typically, your local municipality requires you have a licensed San Diego plumber test your equipment to certify it is up to the proper standards.