How Do Fire Sprinkler Systems Work? Everything You Need to Know

A fire sprinkler system uses a water supply, pipework and sprinkler heads to react when a fire produces enough heat. The heads do not normally respond to smoke, steam or cooking vapours. They are designed to operate when the temperature around them reaches the level set for that particular sprinkler.

In most automatic systems, the sprinkler closest to the fire activates first rather than every head in the building opening together. Water is then released over the affected area to help control or suppress the fire before it has a chance to spread further.

How Does a Fire Sprinkler System Work?

The first step is the generation of heat due to an emerging fire. The increase in temperature ensures that the heat gets to the sprinkler head located above or near the affected area.

Each head contains a heat-sensitive element, often a glass bulb, which keeps the outlet sealed during normal operation. Once that element reaches its rated temperature, it releases the seal and the sprinkler opens.

The sequence normally looks like this:

1. A fire starts and begins producing heat.
2. Heat reaches the nearest sprinkler head.
3. The heat-sensitive element reaches its activation temperature.
4. The sprinkler head opens.
5. Water moves through the pipework towards the open head.
6. Water is distributed over the affected area to help control or suppress the fire.

A smoke alarm has a different job. It is there to detect signs of smoke and warn people in the property, while the sprinkler system reacts to heat and applies water directly to the area involved.

What Activates a Fire Sprinkler Head?

Many fire sprinklers have a glass bulb inside containing a liquid that expands as the temperature rises and, at the rated temperature, the bulb will break and release the seal.

In other models of sprinklers, there is a fusible element used. The particular construction of the element depends on the product itself, as well as its activation temperature, so that sprinkler head selection should depend on the building’s temperature.

Normal smoke from cooking, steam and dust and similar airborne materials cannot produce necessary temperature for activation of the correctly designed fire sprinklers. Mechanical damage is another problem which can lead to unintentional activation of the sprinkler head.

Do All Fire Sprinklers Activate at the Same Time?

No fire sprinkler system works like an automatic sprinkler system you might find in your garden. In a fire situation, each sprinkler head works independently based on the temperature it’s in right next to. If a fire breaks out directly under one, that sprinkler might kick in while the rest stay shut tight.

More heads can activate if the fire spreads and enough heat reaches other parts of the building, but the first sprinkler opening does not automatically trigger every other head.

That local response matters because water is directed towards the part of the property where it is needed instead of being released throughout the whole building.

What Are the Main Components of a Fire Sprinkler System?

A fire sprinkler system is made of loads of different parts all working together.

Water Supply

A fire sprinkler system needs a reliable water supply that can give the amount of water pressure required by the design. Where that comes from depends on the building size, but it might be from the mains water, a water tank, pumps or a mix of these. It all depends on how big the system is and how much water it might need to pump out when one or more sprinklers go off.

The supply has to be considered at the design stage because even a correctly positioned sprinkler cannot perform as intended if the required water is not available.

Fire Sprinkler Pipework

This pipework transports water from the water source to the sprinkler heads installed throughout the protected areas of the building. The material from which the pipework is constructed will depend on various things, including the specification, conditions of installation, nature of system, and approvals required for the work.

Spears® FlameGuard® CPVC fire sprinkler pipework is approved by UL, FM and LPCB for wet pipe sprinkler systems and offers a corrosion-resistant thermoplastic alternative for approved installations. IPS also highlights the hydraulic and installation benefits of FlameGuard® CPVC.

Sprinkler Heads

Sprinkler heads react to heat and distribute water once they operate.

Different heads may have different temperature ratings, spray patterns and installation positions. Their spacing around the building is also part of the overall system design, so they are not simply installed wherever there is room in the ceiling.

Valves and Control Equipment

Valves allow parts of the system to be controlled, isolated or tested. It is also possible for the monitoring equipment to send out a signal if water starts flowing or if there is a change in the condition of the system.

This is essential for the smooth running of the system because it must be in a working state at all times yet accessible for inspection and testing.

What Types of Fire Sprinkler Systems Are There?

There are different types of fire sprinkler systems. Different systems will be installed depending on the building, risk of fire, temperature, and the use of the protected zone.

Wet Pipe Sprinkler Systems

In a wet system, the pipework is permanently filled with water.

When a sprinkler head activates, water can begin flowing through that head straight away because the pipe is already charged. There is no separate stage where water has to fill the network first.

Wet systems are widely used in appropriate buildings where freezing is not expected.

This type of system is particularly relevant to IPS because Spears® FlameGuard® CPVC fire sprinkler pipework is approved by UL, FM and LPCB for use in wet pipe sprinkler systems.

Dry Pipe Sprinkler Systems

Dry systems differ from wet systems in that there is no water in the piping network at all times.

The air or gas is pressurised within the pipework while the water is prevented from entering at another point in the system.

When a sprinkler activates, the pressure drops and the water flows into the pipework to reach the activated sprinkler. This type of system can be particularly useful in areas that may experience freezing temperatures.

Pre-Action Sprinkler Systems

Pre-action systems add another stage before water enters the sprinkler pipework. They use a separate detection arrangement which first has to identify a possible fire condition. Water is then admitted to the piping so that it can be discharged if the appropriate sprinkler operates.

These systems may be chosen where an unwanted water release could cause serious damage to sensitive equipment or materials.

Deluge Systems

A deluge system is different again because the discharge outlets are generally open rather than individually heat-operated in the same way as standard sprinkler heads.

When the detection and control arrangement operates, water can be released through the open outlets across the protected area.

Because of this, deluge systems are associated with specific higher-risk applications rather than normal automatic sprinkler protection in everyday buildings.

How Does a Wet Pipe Fire Sprinkler System Work?

A wet pipe system stays full of water during normal operation, while the sprinkler heads keep that water contained within the network.

If a fire develops, heat reaches the nearest sprinkler. Once the heat-responsive element reaches its operating temperature, the sprinkler head activates and allows water to discharge.

The system water supply then supports continued flow through that open head.

This fairly direct operation is one reason wet systems are widely used where building conditions allow them. There are fewer stages between the sprinkler responding to heat and water reaching the fire.

Spears® FlameGuard® CPVC is approved by UL, FM and LPCB for this type of system, which is why wet pipe applications are the closest fit with IPS’s fire sprinkler offering.

What Pipe Materials Are Used in Fire Sprinkler Systems?

Material of the pipes of the fire sprinkler system should be chosen depending on the building and system requirements. There are two commonly used materials for the pipes – steel and CPVC, but the choice of material depends on the project.

Steel Fire Sprinkler Pipework

Steel has been used in fire sprinklers for decades and remains a popular material. Steel is a strong material and it can be suitable for various uses. Weight of the material, installation process, possibility of internal and external corrosion are among other things to consider.

CPVC Fire Sprinkler Pipework

CPVC is a thermoplastic option used in approved wet fire sprinkler systems.

One of its practical benefits is weight. CPVC is lighter than traditional steel pipework, which can make handling and installation easier. It also offers strong corrosion resistance and does not rust in the way a metal pipe can.

Its smooth inner surface can support good hydraulic performance, while solvent-cement joining avoids some of the installation processes associated with metal pipe.

Spears® FlameGuard® CPVC Fire Sprinkler Systems are designed specifically for this application. Relevant FlameGuard® products carry approvals including UL, FM and LPCB for specified occupancies and uses.

As with any life-safety system, those approvals and the manufacturer’s installation requirements matter. CPVC should only be used where the selected product and application fall within the relevant approvals.

Where Are Automatic Fire Sprinkler Systems Commonly Installed?

Sprinklers are used in many different types of property and are no longer something associated only with factories and warehouses.

Depending on the fire risk, regulations and design, they can be found in:

• residential buildings
• care homes
• student accommodation
• hospitals
• schools
• offices
• hotels
• commercial properties
• warehouses
• libraries
• other protected premises

The system needs to suit the building. A layout and water supply designed for one type of property cannot simply be copied to another without considering the fire risk and applicable requirements.

Fire Sprinkler Systems vs Smoke Alarms

Fire sprinklers and smoke alarms work well together, but they are not interchangeable.

Smoke Alarm	Fire Sprinkler
Detects signs of smoke or fire	Responds to heat
Warns people in the building	Releases water
Does not directly control the fire	Helps control or suppress the fire
Supports evacuation	Acts on the developing fire

While smoke alarms warn the occupants, sprinklers react automatically due to heat and contribute to the control or the extinguishment of the fire. Both can form part of the wider fire safety measures used within a building.

Common Fire Sprinkler Misconceptions

Although the invention dates back to many years ago, there are still people telling the same untrue stories about fire sprinklers operation.

If One Sprinkler Activates, Do They All Activate?

No. In the standard automatic system each sprinkler acts separately on the basis of heat detection. When the heat-sensing mechanism inside the sprinkler reaches the operating temperature, then only the sprinkler that is involved gets activated. The other sprinklers remain closed unless the fire moves to where there is enough heat for them.

Can Smoke or Steam Set Off a Fire Sprinkler?

The operation of a standard heat-sensing sprinkler does not depend on the presence of smoke around. Neither steam nor ordinary moisture nor cooking vapours should activate the sprinkler. The operation is based on reaching the operating temperature by the heat-sensing mechanism.

It is the main difference why fire sprinklers and smoke detectors are considered as two separate components. The smoke detector detects the smoke and warns about fire while the sprinkler responds to heat and releases water. The damage caused by accidental activation of the sprinkler is not counted here. It is one of the reasons why sprinklers and pipework require professional installation and maintenance.

Do Fire Sprinklers Cause Excessive Water Damage?

Any activation of the sprinkler causes water release and thus leads to the water damage. One of the most widespread misunderstandings is how it happens. In a normal automatic system, the sprinkler or sprinklers exposed to enough heat operate locally rather than every head discharging at once.

That allows the system to concentrate water around the developing fire. Its purpose is to prevent a relatively small incident turning into something capable of causing much greater damage to the property or putting lives at risk. It is better to look at sprinkler water damage in that context than to suggest that the system operates without any consequences at all.

Can Fire Sprinkler Pipes Freeze?

A wet sprinkler system contains water, so very low temperatures have to be considered in the design. This does not mean sprinkler protection cannot be used in cold environments. The system type, pipe location, insulation and other measures can all be considered where freezing conditions are possible.

In some buildings, a dry or another specialist sprinkler arrangement may be more appropriate than a normal wet system. The right approach depends on the environment rather than treating freezing as a reason not to use sprinklers at all.

What Should Be Considered When Designing a Fire Sprinkler System?

There is much more to sprinkler design than deciding where the heads should go. The people designing the system need to look at the building, how it is used and the type of fire risk present. Water supply and pipework then have to support the required level of protection.

Typical design considerations include:

• building use
• fire risk
• available water supply
• flow and pressure
• sprinkler layout
• pipe material
• temperature and environmental conditions
• applicable fire protection standards
• product and system approvals
• access for testing and maintenance
• competent installation

Each point can affect the others. A change in sprinkler layout may alter the hydraulic demand, while a change in pipe material or diameter can affect flow through the system.

For that reason, a fire sprinkler installation should be treated as a complete engineered system rather than a collection of separate components.

How Does Pipework Affect Fire Sprinkler System Performance?

The sprinkler head can only release the water that the pipework is able to deliver to it. Pipe diameter, fittings, layout and internal surface all affect how water moves through the network. The design therefore has to provide the required pressure and flow at the sprinkler positions that may need to operate.

Material selection also matters over the life of the system. Corrosion, incorrect jointing, poor support or unsuitable components can all create problems in what is ultimately a life-safety installation. This is why approved fire sprinkler pipework should be selected as part of the complete system rather than treated like ordinary building pipe.

For wet systems, IPS supplies Spears® FlameGuard® CPVC fire sprinkler pipework and also provides CPVC installation training. CPVC fire sprinkler systems should only be installed by suitably qualified and trained personnel.

FAQs

How does a fire sprinkler system detect a fire?

A sprinkler head normally reacts to heat rather than detecting smoke. Inside the head is a heat-responsive element which holds the sprinkler closed until its operating temperature is reached.

Once that happens, the head opens and water is released over the area below it. Smoke alarms and other detection equipment may be present as well, but they perform a different function.

What temperature activates a fire sprinkler?

The activation temperature depends on the sprinkler specification, so there is no single temperature used across every system.

IPS’s current FlameGuard® FAQ gives around 68°C as an example for a commonly used sprinkler head, but different heads are available for different environments. The correct temperature rating should be selected as part of the system design.

Does every sprinkler head activate during a fire?

No. In standard automatic systems, sprinkler heads normally work independently.

The head closest to the fire may activate first, while those further away remain closed. Additional sprinklers may operate if the fire grows and enough heat reaches their location.

Do fire sprinklers work without electricity?

The heat-sensitive part of a standard sprinkler head does not normally need electricity to respond to heat. It is a mechanical or thermal element that releases when its operating temperature is reached.

However, other parts of the installation may rely on power, including pumps, monitoring equipment and alarms. Whether the complete system can operate during a power failure therefore depends on its design.

What type of pipe is used for fire sprinkler systems?

Fire sprinkler systems can use approved steel or CPVC pipework, depending on the system and application.

For appropriate wet systems, CPVC offers a corrosion-resistant and lightweight alternative. Spears® FlameGuard® CPVC, supplied by IPS Flow Systems, is designed specifically for approved fire sprinkler installations.

How long do fire sprinkler systems last?

There is no useful single lifespan that applies to every sprinkler system. Its condition will depend on the pipe material, installation, building environment, inspection and maintenance over time. Regular testing and servicing are therefore more important than assuming that a system should automatically be replaced after a fixed number of years.