DS Pipe and Steel Supply

Backflow Preventers

Backflow preventers ensure no water flows back in the desired direction, ensuring that any chemicals, toxins, or debris won’t return to a clean water supply. When a system loses pressure, water pushed onto the property may flow backward—that’s where backflow comes from. Backflow is dangerous because it can become a pollutant. Contaminants like pesticides, human waste, chemicals, fertilizers, and even stagnant, bacteria-ridden water can get into the clean water supply.

How Do Backflow Preventers Work?

Backflow preventers typically include one or more check valves that allow water to flow in one direction only. These valves are often spring-loaded to ensure they close tightly when water flow reverses. In addition to check valves, backflow preventers may incorporate air gaps or atmospheric vacuum breakers. These mechanisms create a physical barrier between the potable water supply and potential contaminants by introducing air into the system when needed, thereby preventing back-siphonage.

Some backflow preventers employ a reduced pressure zone assembly, particularly those used in high-risk situations. This consists of two check valves separated by a chamber that drains to the atmosphere. If the pressure in the system drops, causing water to flow backward, the chamber allows water to discharge harmlessly rather than contaminating the potable water supply.


In the piping industry, backflow preventers are mandated by building codes and plumbing regulations to protect public health and ensure the safety of drinking water. They are installed strategically within plumbing systems, including where water connections are made to boilers, sprinkler systems, irrigation systems, and fire suppression systems. Regular maintenance and testing of backflow preventers are essential to verify their functionality and compliance with regulations.