Why is lower check valve installation important on FDNY connections?

Lower check valve installation is crucial on FDNY connections primarily to avoid backflow of water. Backflow can occur when there is a change in pressure within the system, potentially allowing contaminated water from the sprinkler system or outside sources to flow back into the potable water supply. The lower check valve acts as a safeguard, ensuring that water can only flow in one direction, thus maintaining the integrity of the water supply and protecting public health. This mechanism is vital in fire protection systems where maintaining cleanliness and safety of the water is essential.

While preventing excessive pressure, limiting water flow rates, and enhancing system efficiency are important considerations in sprinkler systems, the primary function of the check valve is to prevent backflow, making it a critical component in maintaining the safety and efficacy of the firefighting water supply.