What is a primary difference between wet and dry sprinkler systems?

The primary difference between wet and dry sprinkler systems lies in the presence of water in the system's pipes. In wet sprinkler systems, the pipes are constantly filled with water, and when a fire occurs and triggers the system, the water is immediately discharged through the open sprinkler heads. This allows for a quick response to extinguish or suppress a fire.

On the other hand, dry sprinkler systems do not have water in the pipes. Instead, they are filled with pressurized air or nitrogen. Water is only introduced into the system when a fire occurs, causing the air pressure in the pipes to drop and activating the release of water from a storage tank. This design is particularly beneficial in environments where the temperature may drop below freezing, as it prevents water from freezing in the pipes and causing damage.

Thus, understanding that wet systems have water in their pipes is essential for recognizing the fundamental operational differences between these two types of sprinkler systems.