Overview of Backflow Prevention

Safeguarding the public water system is an essential part of our mission to protect public health.

Each connection to our system, whether it is a residential home or a commercial business, presents an opportunity for non-potable water to enter the public water system. 

To protect against this, Charleston Water System has a service area-wide backflow prevention program that is administered by our Cross-Connection Control Department.  

Watch a Video Explaining Backflow (1:55) 




What is backflow?

Backflow can occur when changes in water pressure create a suction effect, which can cause water to reverse flow—to backflow into the public supply.

Without barriers to prevent this, water from private plumbing systems, including industrial plants, pools, and medical facilities, could flow into our public system and impact water quality.

That's why state and federal laws require water utilities to identify all connections to the public supply and have a program in place to prevent backflow. We do this by requiring customers whose water use presents a backflow hazard to install a backflow prevention device and have it tested annually.


About our Cross-Connection Control Department


Our Cross-Connection Control Department administers Charleston Water's backflow prevention program in accordance with our Cross-Connection Control Program Manual. This includes: 

  • Determining whether a customer must install a backflow prevention device, and if so, which type.
  • Developing and maintaining specifications for installing backflow prevention assemblies.
  • Inspecting newly installed backflow preventers.
  • Maintaining records of all customer backflow preventers in our service area and annual backflow test results for each.
  • Certifying third-party Backflow Testers and maintaining the Approved Tester List.
  • Issuing permits for use of fire hydrants as a temporary water supply and ensuring proper backflow precautions are taken.
Charleston Water System does not install or test backflow preventers. 

Customers are responsible for having their backflow preventer installed according to our specifications and getting it tested annually by a third-party tester from our Approved Tester List. Backflow preventers are part of a customer's private plumbing system.