How Fire Sprinklers Work and the Damage They Can Cause

Summary: Fire sprinklers can save lives and property, but they can also leave a mess behind. Learn how they work, the different types, and what to do if yours ever go off.

Fire sprinklers are one of the most effective life- and property-saving systems in commercial and residential buildings. They’re commonly found in hotels, apartments, warehouses, and office buildings — yet many people don’t know exactly how they work or the damage they can sometimes cause.

In this guide, we’ll cover:

1. How fire sprinklers are triggered and function
2. The main components of a sprinkler system
3. Water supply and deactivation
4. Common causes of sprinkler malfunctions
5. Types of fire sprinkler systems
6. What to do after sprinkler-related water damage

How Do Fire Sprinklers Work?

Fire sprinklers are designed to detect heat, not smoke. This is a common misconception — burnt toast won’t set off your building’s sprinklers. Here’s how they operate step-by-step:

Heat Triggers the Sprinkler Head

When a fire starts, hot air rises to the ceiling. Inside each sprinkler head is a small glass bulb filled with a glycerin-based liquid. Once the surrounding air reaches 135–165°F (57–74°C), the liquid expands, shattering the bulb.

Water is Released and Pressurized

Behind the sprinkler head is a valve connected to a water supply. When the bulb breaks, pressurized water is released and sprayed in an arc to control or extinguish the flames.

Only Activated Heads Discharge

Contrary to what you see in movies, only the sprinklers near the heat source activate. This reduces water usage and limits damage to unaffected areas.

Did you know? Sprinklers use six times less water than a firefighter’s hose, greatly reducing water damage.

Key Components of a Fire Sprinkler System

Component	Purpose
Sprinkler Head	Heat-sensitive trigger that releases water onto the fire.
Water Pipes	Deliver water from the main supply to the sprinkler heads.
Control Valve	Allows manual shutoff or activation; sometimes linked to fire alarms.
Water Supply	Can be municipal water or a dedicated storage tank for reliability.

 Types of Fire Sprinkler Systems

Knowing what type of sprinkler system your building has isn’t just a detail for the maintenanceMaintenance is the routine care, inspection, and repair of a... More log — it’s a big part of making sure it works when you need it most. Each type is designed for specific environments and safety needs:

1. Wet Pipe Systems – The most common and straightforward design. These pipes are always filled with water, so when a sprinkler head activates, water flows immediately. Wet pipe systems offer the fastest response time, making them ideal for most commercial buildings where freezing isn’t a concern.
2. Dry Pipe Systems – Instead of being filled with water, these pipes hold pressurized air. When a sprinkler head activates, the air is released first, allowing water to enter the pipes. This slight delay is worth it in unheated areas like warehouses or parking garages, where standing water could freeze and damage the system.
3. Pre-Action Systems – These are a bit more high-tech and cautious. They require a separate fire detection system to trigger the release of water into the pipes before a sprinkler head can go off. Because of their extra safeguard against accidental discharge, they’re often found in places where water damage would be devastating — think museums, archives, or data centers.
4. Deluge Systems – All sprinkler heads remain open, and when the system activates, water flows through all of them at once. This is used in high-hazard areas where a fire could spread quickly, such as aircraft hangars or chemical processing plants.

Risks and Causes of Sprinkler Malfunctions

Fire sprinkler systems are engineered to be extremely reliable, but no system is completely immune to problems. Sometimes, the very system meant to protect your property can cause significant water damage if something goes wrong. Common causes of sprinkler malfunctions include:

• Mechanical Damage or Defective Parts – A damaged sprinkler head or faulty valve can trigger an accidental discharge.
• Excessive Heat Exposure – Heat sources like ovens, industrial equipment, or even strong lighting placed too close can cause a head to activate unintentionally.
• Corrosion – Over time, moisture and oxygenOxygen is a chemical element essential for combustion and li... More can leadLead is a heavy metal that can be toxic to humans, especiall... More to rustRust is a reddish-brown oxide that forms on iron or steel du... More inside pipes or on sprinkler components, which can weaken the system and cause leaks.
• Freezing Temperatures – If water inside the pipes freezes, it can cause cracks or bursts, leading to floodingFlooding is the overflow or accumulation of water in areas t... More when temperatures rise.
• Improper Installation – A poorly installed system may be prone to failures, reduced coverage, or accidental triggers.
• Tampering or Vandalism – Untrained individuals interfering with the system can cause accidental activation or disablement.

Related Read: Three Things to Consider Before Installing a Fire Sprinkler System

Water Supply and Deactivation

A sprinkler system is only as effective as its water source. Most are connected directly to the municipal water supply, ensuring immediate pressure when a head activates. In some buildings — especially in areas with unreliable water service — the system may be fed by a dedicated fire water tank for added reliability.

Deactivation happens in one of two ways:

• Automatically – Once the fire is out and the temperature drops, the system stops discharging.
• Manually – A control valve can shut off water flow, but in most commercial settings, only trained personnel or the fire department should do this.

In an emergency, the fire department typically takes control of shutting off the system after confirming the fire is fully contained.

Fire Sprinklers and Water Damage Restoration

Fire sprinklers do a great job of stopping a fire before it spreads, but the water they release can still leave behind a mess. It’s not unusual to find:

• Floors that are warped or starting to buckle
• MoldMold is a type of fungus that grows in damp or humid conditi... More beginning to grow within just a day or two
• Walls, drywall, and insulationInsulation is a material used in buildings to reduce the tra... More soaked through
• Electrical problems if water reaches outlets or wiring

If your sprinklers go off, timing is everything. Acting quickly can make all the difference — not just in saving your property, but in making the cleanup process faster and less expensive.

Here’s what you should do right away:

• Turn off the water supply if it’s safe to do so.
• Take plenty of photos and notes to document the damage for your insurance company.
• Call a fire and water damage restorationWater damage restoration is the professional process of clea... More pro who can start cleanup and repairs immediately.
• Get the dryingDrying is the process of removing moisture from materials, s... More process started fast to keep moldMold is a type of fungus that grows in damp or humid conditi... More and structural damage from setting in.

Curious about the most common reasons sprinklers accidentally flood buildings? Read our guide on why fire sprinkler systems flood buildings and the risks involved.

Call a Certified  Restoration Company

Fire sprinklers are a critical fire safety investment that can save lives and drastically reduce property loss. Knowing how they work, understanding their components, and preparing for potential water damage ensures you’re fully protected.

If your sprinklers have gone off — whether from a real fire or an accident — don’t wait. Contact a certified water and fire damage restoration team to prevent long-term damage and keep your building safe.

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