Backflow Requirements for Residential Customers

Residential customers are required to have a backflow preventer in the following cases:

  • You have an in-ground irrigation system
  • You have a separate irrigation meter
  • You have a dock with water service
Typical backflow prevention assembly for a residential irrigation system
 If you plan to install an irrigation system
  1. Notify us. Contact us before you install an irrigation system.
  2. Complete a questionnaire. We’ll send you a form to complete. Based on your answers, we'll send you information about the type of backflow assembly you need to install.
  3. Install the backflow preventer. Be sure to install it according to our specifications. We recommend hiring a professional installer. Provide the installer with a copy of the letter and accompanying information.
  4. Inspection. Once it's installed, contact us to schedule an inspection by one of our Backflow Inspectors (if you hired an installer, he/she will contact us on your behalf). Call the Inspection Request Line at 843-727-6981 or email
  5. Test. Contact a third-party Backflow Tester from our Approved Tester List
    to test the backflow preventer. The tester will submit the results to us.
  6. Annual Test. The backflow assembly must be tested annually by a tester from our Approved Tester List. We'll notify you by mail when it's time for your annual test.
If you already have a backflow preventer
You’re responsible for having it tested annually by a third-party Backflow Tester from our Approved Tester List. We will notify you by mail when it’s time for your backflow test. 

Provide a copy of the reminder letter to your Backflow Tester. This will give the Tester the information he needs to submit the results to Charleston Water System. Testers have the forms to be submitted to CWS.