Lower check valves must be fitted on FDNY connections to prevent what?

Lower check valves are crucial components in fire suppression systems, particularly in the context of connections to the Fire Department of New York (FDNY). Their primary function is to prevent backflow of water, which refers to the unintended reversal of water flow within a piping system.

In the event of a fire or emergency situation, water is drawn from the fire hydrant or other sources into the sprinkler system to combat flames. If there were no check valves in place, water could flow backward into the municipal water supply, potentially contaminating it with substances from the fire suppression system. This not only poses health risks but also violates public health regulations.

Thus, the installation of lower check valves effectively ensures that water cannot flow back out of the sprinkler system, maintaining the integrity of both the fire protection system and the surrounding water supply. Their role in preventing backflow is essential for safety compliance and for protecting the public and firefighting resources.