What is the main difference between wet and dry fire sprinkler systems?

The main difference between wet and dry fire sprinkler systems lies in their operational state regarding water presence. Wet systems are always filled with water, meaning that the pipes are under pressure at all times and can immediately release water when a sprinkler head is activated by heat from a fire. This immediate flow is crucial for combating fires effectively and quickly, making wet systems particularly suitable for environments that are not subject to freezing temperatures, where water can remain liquid without risk.

In contrast, dry systems are filled with air or nitrogen and only release water upon activation. This design is essential in freezing environments, where allowing water to sit in the pipes could lead to freezing and potential system failure. Thus, the core distinction is that wet systems are pre-filled with water ready to spray, while dry systems wait until the heat-triggered activation to introduce water into the system. This fundamental operational difference ensures that the two systems serve specific needs based on environmental conditions.