Above: Leaving a hose in standing water, such as this pool, can lead to backflow contamination. When there is high demand for water in one part of the water system, such as during a main break, this can lead to low water pressure. Water from private plumbing can then be sucked back into the water main lines, bringing potential contaminants into contact with our public water system.
Protecting Our Water System
Water normally flows from the public water system into your home or business, but backflow is the “backwards flow” of water from private plumbing systems into the public water system. Backflow can carry harmful contaminants and bacteria into the public water system, which can lead to illness, injury and, in some cases, death. Watch this video or read this brochure for more information.
Montgomery County Environmental Services is responsible for protecting the public water system from backflow and ensuring the safety of our public drinking water supply. Since 1993, our department has required the installation of backflow devices on commercial and residential water services that pose a potential hazard or threat to the public water system. This helps to minimize health risks and ensure the safety and purity of our drinking water.
Installing Backflow Prevention Devices
Our department requires commercial and residential customers to install a testable backflow prevention device when their plumbing installations pose a hazard to the public water system. This device prevents water from flowing backward into the water supply.
Customers must install and maintain the required backflow prevention device. Failure to do so poses a threat to the public water supply, and may result in water service being disconnected.
If you would like to look up a backflow-certified plumber/tester, please click here for a list of qualified plumbers and testers.
If you are a plumber and would like to submit a backflow test result, please visit our online test site. If it's your first time using our online test submission site, you might want to read our Backflow Online Test Submission User Guide.
Backflow Prevention Regulations