Backflow Preventers

Information on Backflow Preventers

Cross connection devices, known as backflow preventers or check valves, are required on every water service in the Town of Christiansburg per Chapter 36, Article V, Section 36-123 of the Town Code. These devices come in a variety of sizes and models. The required device type will be determined on the proposed use of the water.

Backflow preventers protect the public water supply against cross connection to possible contaminants that could be siphoned back into the public water supply.

Device Details

The principles of the backflow prevention and cross connection are less complicated than some think. The backflow device consists of a series of check valves held in place by springs. Incoming water pressure pushes the checks or rubber discs open. In the event of a pressure drop on the incoming side of the device, the springs will push the checks closed to reduce the possibility of siphoning any contaminants into the public water supply.

Backflow preventers are divided into two types. The residential models are a nontestable low-hazard device. Due to the low risk of potential cross connection to toxic liquids these devices do not require an annual test or inspection. The second type of backflow preventers (RPZ) are ones that require annual testing to insure proper operation. These devices are installed on medium to high hazard water services where the potential for cross-connection is increased.


The Town requires permits for installing and testing backflow devices. Only Virginia state-certified testers can perform the required annual inspection of the testable devices. The backflow reports (PDF), with permit (PDF), must be turned in to the Building Department annually.

Letter to Testing Companies (PDF)

Letter to Businesses (PDF)

For further information, please contact the Building Department.