Note: For all State of Illinois installations.
The State of Illinois plumbing code requires a double check backflow preventor as a minimum base requirement. Please be sure to review the code section concerning the issue in reference to the diagram shown at the right. Also, check with your local municipality to see if they have more requirements.
184.108.40.206.3.2 Piping Installation
A listed backflow prevention device shall be considered a check valve, and an additional check valve shall not be required.
Each source of water supply must have check valve to isolate the supplies from each other. In a fire situation, water flows from the highest pressure source. Fore example, consider a system supplied by a gravity tank, a city connection, and a fire department connection. The gravity tank has the highest pressure source. Initial flow would be from the gravity tank. If the tank’s pressure dropped below that of the city connection, the tank’s check valve would close and the supply would come from the city. When the fire department connected onto the system, the check valves in both automatic supplies would close and the supply would come through the fire department pumps via the fire department connection.
220.127.116.11 Backflow Devices
Where backflow prevention devices are installed, they should be in an accessible location to provide for service and maintenance.
16.2.5 Backflow Prevention Assemblies
18.104.22.168The minimum flow rate shall be the system demand, including hose stream demand where applicable.
Backflow prevention assemblies are covered in 22.214.171.124 and 126.96.36.199. Additional information on the testing of backflow devices is provided in 188.8.131.52. Due to their affect on sprinkler systems, backflow prevention devices must be accounted for through hydraulic analysis and flow testing
|184.108.40.206||The backflow prevention assembly shall be forward flow tested to ensure proper operation.|
220.127.116.11.2.1Valves shall be provided as illustrated in Figure 18.104.22.168.2.1.
|22.214.171.124.2||Connections Between Antifreeze System and Wet Pipe System with Backflow Prevention Device Installed.|
126.96.36.199.2.3The expansion chamber shall be sized based on the minimum and maximum volume of the antifreeze solution over the life of the system.
|188.8.131.52.2.2||An expansion chamber shall be provided as illustrated in Figure 184.108.40.206.2.1.|
What is in a check valve?
A valve which permits flow in one direction, from the supply to the end use.
What is in a double check valve?
This assembly consists of two internally loaded check valves, either spring or internally loaded, weighted, installed as a unit between two tightly closing resilient-seated shutoff valves as an assembly, and fittings with properly located resilient seated test ports or cocks.
What is a reduced pressure zone?
Two independently acting check valves together with a hydraulically operating, mechanically independent pressure differential relief valve located between the check valves and below the first check valve. These units are located between two tightly closed resilient seated shutoff valves, as an assembly, and are equipped with properly located resilient seated test cocks.