Fire Sprinkler Systems: Guide

There are four main types of fire sprinkler systems:

• Wet pipe
• Dry pipe
• Deluge
• Pre-action

Cold water is stored under pressure in the pipes of a wet pipe fire sprinkler system, which is the most popular type in residential structures and is discharged promptly by sprinkler heads when a predefined heat threshold is achieved.

Dry pipe sprinkler systems take somewhat longer to activate and are utilized in unheated/unoccupied buildings where pipes can freeze and rupture.  Nitrogen gas or pressured air is held in pipes that are connected to a water storage tank or main. When a fire activates the pipes, the air seeps out, forcing water to flow through the pipes to the sprinkler heads.

Deluge sprinkler systems are often employed in situations where quick fire damage is a major issue, such as warehouse loading bays and high-rise structures. In these systems, the nozzle is always open.  They are activated by an alarm, which activates a water release valve.

Pre-action sprinkler systems are a combination of wet and dry pipe systems that are often employed in locations that are at high risk of water damage.  Water is not held in the pipes until a fire is detected, at which point it is discharged to the sprinkler heads. The response time is the same as that of a normal wet pipe sprinkler system. Automatic fire sprinkler systems are also available and effective in large areas such as offices and retail malls.

SMART (Simultaneous Monitoring, Assessment, and Response technique) sprinklers are being developed, which use more than one detection technique and should react faster.

Sprinklers that expel water mist rather than water are another option.

Fire Sprinkler Heads

A fire sprinkler head is a part of a sprinkler system that releases water when a fire is detected. It is available in a variety of designs.

Each sprinkler head has a trigger mechanism that opens to spray water on the fire.

Some water is discharged into the ceiling using conventional heads, which are acceptable for most residential fire sprinkler systems.

Upright or pendant spray sprinklers direct all of the water straight down and are ideal for high-ceilinged rooms.

Heads can be sunk in the ceiling or covered with resin caps to make them more aesthetically pleasing.

Sidewall sprinklers are attached to the wall at a high position. They often provide more water coverage than standard sprinkler heads.

The plug within the head that holds back the water may be made of Wood’s metal, a meltable alloy of bismuth, lead, tin, and cadmium, or a small glass bulb containing a glycerin-based liquid that expands and shatters when heated, releasing the water.

Each sprinkler head operates on its own. Only sprinklers located above the fire will be activated, increasing water pressure over the fire and decreasing fire and water damage to the building. Sprinklers consume significantly less water than fire hoses.

Fire Sprinkler Installation

A fire sprinkler system, whether residential or commercial, should only be installed by a business accredited by a respected organization, such as a CASA member.       

Only third-party tested and approved hardware and components should be utilized.  When retrofitting, the location of existing pipes, electrical fittings, and mains water pressure must all be addressed. A water storage system can be required.