Republic Fire - Sprinkler System Overview

Fire Sprinkler Systems

A fire sprinkler system is an active fire protection measure, consisting of a water supply system, providing adequate pressure and flowrate to a water distribution piping system, onto which fire sprinklers are connected. The fire sprinkler system provides essential operations within a building space are intended to either control the fire or to suppress the fire.

There are various types of fire sprinkler systems. One involves having pressurized water in the pipes at all times, ready to spray, while a dry system is a “water on demand” system. Each system has its advantages and disadvantages.

Wet Fire Sprinklers:

By a wide margin, wet pipe sprinkler systems are installed more often than all other types of fire sprinkler systems. They also are the most reliable, because they are simple, with the only operating components being the automatic sprinklers and (commonly, but not always) the automatic alarm check valve. An automatic water supply provides water under pressure to the system piping.

Operation - When an automatic sprinkler is exposed for a sufficient time to a temperature at or above the temperature rating, the heat sensitive element (glass bulb or fusible link) releases, allowing water to flow from that sprinkler.

Dry Pipe Systems:

Dry pipe systems are installed in spaces in which the ambient temperature may be cold enough to freeze the water in a wet pipe system, rendering the system inoperable. Dry pipe systems are most often used in unheated buildings, in parking garages, in outside canopies attached to heated buildings (in which a wet pipe system would be provided), or in refrigerated coolers. Dry pipe systems are the second most common sprinkler system type. In regions using NFPA regulations, dry pipe systems cannot be installed unless the range of ambient temperatures reaches below 40F.

Operation - Water is not present in the piping until the system operates. The piping is filled with air below the water supply pressure. To prevent the larger water supply pressure from forcing water into the piping, the design of the dry pipe valve (a specialized type of check valve) results in a greater force on top of the check valve clapper by the use of a larger valve clapper area exposed to the piping air pressure, as compared to the higher water pressure but smaller clapper surface area.

When one or more of the automatic sprinklers is exposed to for a sufficient time to a temperature at or above the temperature rating, it opens, allowing the air in the piping to vent from that sprinkler. Each sprinkler operates individually. As the air pressure in the piping drops, the pressure differential across the dry pipe valve changes, allowing water to enter the piping system. Water flow from sprinklers needed to control the fire is delayed until the air is vented from the sprinklers. For this reason, dry pipe systems are usually not as effective as wet pipe systems in fire control during the initial stages of the fire.

For more information regarding fire alarm installation or inspection services please contact our service department at (877) 749.FIRE (3473) or email us at This e-mail address is being protected from spambots. You need JavaScript enabled to view it.