What is meant by "wet" in dry valve sprinkler systems?

The concept of "wet" in dry valve sprinkler systems primarily refers to the mechanism that prevents water from remaining in the pipes until the system is activated. In dry systems, which are typically utilized in environments where the risk of freezing exists, the pipes are filled with air or nitrogen instead of water. When a fire activates the sprinkler, the dry valve opens, allowing water to rush into the system and flow through the pipes to the individual sprinkler heads.

This design is crucial for maintaining the integrity of the system in cold conditions, as it ensures that freezing temperatures do not lead to water freezing inside the pipes and causing damage. The quick activation of the water supply upon detecting a fire is a critical safety feature of dry valve systems, emphasizing the importance of understanding how water is managed within these systems.