Systems

Sprinkler System Types

Wet

A wet system holds water that will discharge out of a sprinkler head upon activation. A common misperception of this system is that all sprinkler heads will discharge at the same time.

FACT: Only heads activated by heat or fire will discharge water. A wet system is the most frequently used fire suppression system.

Dry

A dry system is filled with air, instead of water. This system is ideal for unheated spaces, freezing temperatures and exterior canopies. Once a sprinkler head is activated, the air is released out of the system’s piping, opens the dry valve and allows water to enter into the sprinkler system.

Preaction

There are two (2) types of preaction systems: a single interlock preaction system and a double interlock preaction system. Both of these preaction systems are similar to a dry system, in that the pipes are filled with air, but:

• A single interlock preaction system will only discharge water if the system loses air pressure or a smoke or heat detector is activated; and,
• A double interlock preaction system will only discharge water if two (2) actions occur: one of these being the activation of a sprinkler head and the other being the activation of a smoke or heat detector.

Preaction systems are typically used in more sensitive building applications, i.e., computer data or server rooms. They are designed in this fashion to eliminate the discharge of water if, for example, a head is accidently knocked off. Although the single preaction system is cheaper, the double system is used more frequently because the dual action requirement reduces the possibility of water discharging due to accidental activation, i.e., knocking a head off, etc.

Deluge

A deluge system is an open head nozzle system. It is designed to allow every sprinkler head in the system to discharge water simultaneously, i.e, if one head is activated, they will all activate and discharge water. This type of system is typically used on tank farms or with propane tanks, basically areas that host highly flammable and/or combustible tanks.

Foam

A foam system is similar to a wet system in that water is stored in the pipe, but, at the riser, a foam tank and mixing valve combine the foam and water to the proper concentration so foam will discharge out of the heads instead of water. This type of system would be appropriate where chemicals are used that water will not control when combusted.

Antifreeze

In an antifreeze system, pipes are filled with a premixed antifreeze solution based on the freezing point of that area. This type of system may be suitable for small, outdoor loading docks or in exterior coolers or freezers. They have been used as an alternative to a small dry system because they are cheaper. Nevertheless, under new regulations and codes, this type of system can only be used with an approved and listed solution. Currently, there are no solutions that have been approved or listed.

Alarm system

Fire alarm overview

An alarm system monitors a suppression system for sprinkler activation and/or tampering activity. Upon activation, the system resounds and notifies the alarm monitoring company and/or fire department of the issues detected to facilitate a proper and timely response.

Smoke detector

Smoke detection overview

Smoke detectors are designed to alert the occupants of a building that a fire has been ignited. Upon activation, either by a manual pull station, smoke and heat detector or sprinkler water flow device (if installed), a horn will sound, often accompanied by flashing lights.