What distinguishes a wet pipe system from a dry pipe system?

A wet pipe system is characterized by having water continuously maintained in the piping and sprinkler heads, so it is readily available to be released during a fire event. This immediate availability of water allows for rapid activation when the system detects heat from a fire, which can help to quickly suppress the flames.

In contrast, dry pipe systems are filled with pressurized air or nitrogen, which keeps the water in the supply lines held back in a storage tank until needed. When a fire occurs, the heat activates the sprinkler head(s), causing the air pressure to drop and subsequently allowing the water to flow into the piping and reach the sprinkler heads.

The option highlighting that water is always present in wet pipe systems captures this fundamental difference effectively. It illustrates the primary function and readiness of wet pipe systems, especially in environments where quick access to water for fire suppression is crucial. This characteristic makes the wet pipe system suitable for a range of applications, primarily in areas where freezing is not a concern.