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Sprinkler Systems: How They Work & Why Maintenance Matters

Fire Safety Guide #17 | An in-depth look at how sprinkler systems operate and why regular maintenance is essential for reliable fire protection.
Sprinkler systems are among the most effective tools for controlling and suppressing fires. They have been protecting lives and property for more than a century and remain a cornerstone of modern fire safety strategies across homes, commercial buildings, and industrial facilities. But how do they actually work — and why is regular maintenance
so important?

How Do Sprinkler Systems Work?

Contrary to popular belief, sprinklers do not all activate at once when a fire breaks out. Each sprinkler head is designed to operate individually in response to heat, ensuring that water is released only where it is needed.

Each head contains a heat-sensitive element, such as a glass bulb filled with liquid or a fusible metal link. When the air around it reaches a set temperature — typically between 68°C and 74°C in standard systems — the element bursts or melts, opening the sprinkler head. Water is then discharged directly onto the fire below, suppressing the flames before they spread out of control. Only the sprinklers closest to the fire activate, minimising unnecessary water damage compared to the far greater destruction caused by an uncontrolled blaze.

Types of Sprinkler Systems

There are several types of sprinkler systems, each designed for different environments and risks.

The most common is the wet pipe system, where pipes are constantly filled with water, ready for immediate discharge. In colder environments where pipes might freeze, dry pipe systems are used; these are filled with pressurised air or nitrogen until activation allows water to flow in.

Deluge systems are designed for high-risk industrial sites. All sprinkler heads remain open and release water simultaneously when triggered, providing rapid saturation. Pre-action systems combine features of dry and wet systems, requiring a separate detection event, such as a smoke or heat alarm, before water enters the pipes. These are commonly used in sensitive environments like data centres, museums, and archives where accidental discharge must be avoided.

Why Sprinklers Are Effective

Sprinkler systems offer rapid response, often controlling a fire before emergency services arrive. By containing flames and smoke, they provide valuable time for occupants to escape safely. Their effectiveness also reduces structural damage and protects business continuity.

The statistics speak for themselves: sprinklers operate in around 94% of fires where they are installed, successfully controlling or extinguishing the fire in the majority of cases.

Maintenance Requirements

Like any fire protection system, sprinklers must be properly maintained to remain reliable. A neglected system may fail when it is needed most.

Regular checks are essential. Weekly visual inspections should confirm that valves are open, gauges show the correct pressure, and there are no visible leaks. Monthly inspections test water flow alarms, pumps, and control valves, while quarterly testing ensures alarm devices, water supplies, and monitoring equipment are functioning correctly.

Annual servicing by a qualified engineer is critical, covering pumps, water tanks, and a sample of sprinkler heads. More in-depth checks are carried out at five-year intervals and beyond, including pipe flushing, internal inspections, and system upgrades. In the UK, maintenance requirements are set out in standards such as BS EN 12845, which governs fixed firefighting systems and automatic sprinklers.

Common Issues That Affect Sprinkler Systems

Several issues can compromise a sprinkler system if left unchecked. Corrosion inside pipework may lead to blockages, while obstructions around sprinkler heads reduce water coverage. Accidental damage, painted or tampered heads, and closed valves can all prevent sprinklers from operating effectively. Regular servicing ensures these problems are identified and resolved before they undermine safety.

Conclusion

Sprinkler systems are a proven, cost-effective defence against fire. They respond automatically, protect lives, and reduce damage — but only when properly designed, installed, and maintained. Regular inspections and servicing are not just good practice but essential to ensure that this critical fire protection system is always ready to perform when it matters most.
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