Backflow Requirements for Commercial Customers

We evaluate backflow requirements for businesses on an individual basis when a water account is established. 

Businesses that present a potential backflow hazard are required to install the appropriate backflow prevention device and have it tested annually.


Backflow prevention assembly for a commercial water service
We determine backflow hazard by evaluating the type of business, how the business uses water, and what type of equipment or appliances are connected to the building’s water supply system. 

One way we determine backflow hazard is by asking customers to complete a Backflow Assessment Form to gather more information about their water use. 

Types of businesses that are required to install a backflow preventer include:

  • Restaurants
  • Dry cleaners
  • Medical offices
  • Funeral homes
  • Beauty and nail salons
  • Car washes
  • Multi-tenant retail space
  • Any commercial building three stories or taller
  • Any commercial space with a dedicated fire service line / sprinkler system
  • Churches with baptismal pools
Other businesses may be required to install a backflow preventer based on backflow hazard.

If a backflow preventer is already installed
If your commercial property already has 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. 

Please provide a copy of the reminder letter to your Backflow Tester. The letter will give the Tester the information he needs to submit the test results to Charleston Water System. 

If you are required to install a backflow preventer
We will notify you by mail if a backflow preventer must be installed. In some cases, we may first ask you to complete a System Protection Questionnaire Form to gather more information. 

The letter will include instructions on which type of backflow preventer to install and installation specifications. Follow these steps:

  1. 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.
  2. 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 our Inspection Request Line at 843-727-6981 or email backflow@charlestoncpw.com. 
  3. Test. Contact a third-party Backflow Tester from our Approved Tester List to test the backflow assembly. The tester will submit the results to us.
  4. Annual Test. The backflow assembly must be tested annually by a third-party Backflow Tester from our Approved Tester List. We'll notify you by mail when it's time for your annual test.
Questions? Contact us.