How Automatic Fire Sprinkler Systems Work: Types, Parts and Myths Corrected

Fire sprinklers appear in many films going off all at once because someone lit a cigarette, which has fixed a wrong idea in people's minds: that they flood a room at the first whiff of smoke. The engineering reality is quite different. In this article we explain how a single sprinkler works, what the network consists of, the types of system, when they are required in Saudi buildings, and why they should only be installed or modified by a licensed contractor.

How does an automatic fire sprinkler system work?

The Home Fire Sprinkler Coalition (HFSC) (external source via the Consumer Safety Center) explains the idea simply: a sprinkler is a plug that holds water back inside a pipe much like ordinary plumbing. The heat of a fire breaks a small glass bulb containing a heat-sensitive liquid, or melts a metal solder link, so the plug opens and water rushes onto a deflector that spreads it as a spray over the fire.

The key point is that operation depends on heat, not smoke. The same source confirms that only the sprinkler closest to the fire opens while the others stay closed, so the water is confined to the area of the fire.

The main parts of the network

• A reliable water supply: a dedicated fire tank or a public network with enough pressure, depending on the design.
• Fire pump: raises the pressure when needed, usually with a small jockey pump that keeps the pressure up.
• Main control valve and alarm station: open and close the supply and give a signal when water flows.
• Main and branch pipes: distribute water to the zones of the building.
• Sprinkler heads: pendent, upright or sidewall, with different operating temperatures set by the manufacturer and the design.
• Pressure gauges and a Civil Defense connection: to monitor the system and to support it from fire engines in buildings that require it.

Each part has a job, and the system is only as reliable as its weakest link. A perfect network with a closed valve or a pump room used as a store will not perform on the day, which is why the owner's daily observations, listed later, matter as much as the design.

Which types of sprinkler system exist and which suits a building?

The standard NFPA 13 for the installation of sprinkler systems (external source via the Consumer Safety Center) covers the design and installation of these systems, and a version for small dwellings exists as NFPA 13D. Systems are usually divided into four main types, according to what fills the pipes and how they are triggered:

In the hot Saudi climate there is normally no freezing risk in residential buildings, so the wet system usually prevails for its simplicity and fast response. However, roof surfaces and exposed pump rooms need care to protect pipes and equipment from sun and corrosion.

Sprinkler myths versus facts

The HFSC sprinkler facts page (external source via the Consumer Safety Center) states that 90% of home fires are contained by the operation of a single sprinkler, and that a sprinkler can contain or extinguish a fire in less time than fire crews take to arrive. These figures come from the American context, but they illustrate a working principle that does not change from country to country.

When are sprinklers required in Saudi buildings?

The Saudi Fire Protection Code SBC 801 and the Civil Defense regulations decide which buildings must have sprinklers, according to occupancy type, area, height and number of occupants. Private villas are not normally required to have them in the way hotels, hospitals, commercial complexes and towers are, but the deciding reference is always the approved drawings of your own building.

Because the network is tied to pumps, tanks and calculated pressures, its design, installation, testing and maintenance are carried out by a safety contractor licensed by Civil Defense. A sprinkler head must not be moved, and a false ceiling or plasterboard partition must not be added beneath the heads, without consulting the designer, because that can block the spray from the protected area. For the general framework, read our overview of Civil Defense building requirements.

What should you do if a sprinkler goes off in the building?

1. 1

   Evacuate first

   A sprinkler operating means real fire heat is present; get everyone out and call Civil Defense on 998.

2. 2

   Do not close the valve yourself

   Shutting off the supply before the fire is confirmed out can let the fire return. Leave the decision to the fire service or the specialist.

3. 3

   Contain the water once allowed in

   When entry is permitted, lift furniture and equipment and dry the area to reduce damage to floors and walls.

4. 4

   Replace the head and restore the system

   A head that has operated is not reused; a specialist replaces it with the same specification, then refills and tests the network.

What should an owner or building manager watch for daily?

These are observations for the owner only. Periodic inspection and testing follow a schedule and records handled by a specialist, as we explain in our guide to fire network maintenance. To arrange an assessment or request a licensed contractor, you can contact us through our safety systems and fire protection page. And if you notice leakage from fire pipes inside ceilings, you may also need water leak detection to find the source before it damages the finishes.