Why is a check valve with a 3/32" hole in the clapper required in freezer spaces?

The presence of a check valve with a 3/32" hole in the clapper is primarily to prevent the evaporation of priming water in freezer spaces. In these environments, maintaining a certain level of water in the sprinkler system's piping is critical for its operation; this water helps ensure that the system can activate effectively in the event of a fire.

The small hole allows air to enter the system, which prevents the formation of a vacuum when the water is drained or if temperatures fluctuate. This is essential because if the water were to completely evaporate or if a vacuum were created, it could lead to a malfunction in the system, preventing it from delivering water when needed.

In freezer spaces where the temperature is below freezing, if water were to evaporate from the system or if a vacuum was maintained, the risk of the system failing to operate properly increases significantly. Thus, the check valve's design incorporating the hole is a preventive measure against this issue.