wetpipe

A wet pipe system is a type of automatic fire sprinkler system in which the sprinkler piping is permanently filled with pressurized water. The pipes run through the building and are connected directly to a water supply. When a sprinkler head is heated to its activation temperature, it opens and water is released immediately into the piping and out of the activated head. This rapid response is a primary characteristic of wet pipe systems.

Key components include the water-filled piping network, sprinkler heads, risers, and a main water supply. The system typically features a control valve, such as a main control valve or post-indicator valve, and an alarm mechanism that signals water flow to the fire alarm system. In many installations, an alarm valve and a water-flow alarm provide both a visual/audible indication and a supervisory signal if the valve is not in the correct position or if water flows.

Operation and performance: once a head is activated, water discharges into the piping and the remaining heads receive water as needed. The water supply must be continually pressurized to ensure immediate discharge from any activated head. The system is designed for rapid detection and notification, often triggering fire alarms in parallel with sprinkler discharge.

Advantages and limitations: wet pipe systems offer fast response, relatively simple design, and lower initial cost with fewer moving parts. They are well-suited for occupied buildings with year-round heat and reliable water supplies. However, they are susceptible to freezing in unheated or improperly protected spaces, and a single damaged head can release a substantial amount of water, potentially causing water damage.

Standards and use: wet pipe systems are common in commercial, institutional, and many industrial buildings. They are guided by standards such as NFPA 13 (Standard for the Installation of Fire Sprinkler Systems). In areas prone to freezing, alternative systems or temperature protection measures may be used.