In a wet pipe sprinkler system, what is always present in the pipes?

In a wet pipe sprinkler system, water is always present in the pipes. This system is designed to have water continuously available in the sprinkler piping, which allows for immediate discharge when the system is activated by heat from a fire. The use of water provides an effective and rapid means of fire suppression as it quickly dampens flames and cools the surrounding area.

The presence of water in the system also means that it is important for the system to be maintained properly to avoid freezing issues in colder climates or any potential leaks that could compromise the integrity and effectiveness of the sprinkler system. This design contrasts with other types of systems, such as dry pipe systems, where air is present in the pipes until the system is activated, and thus, water is not stored in the pipes.