Understanding Electric and Diesel Fire Pumps: How They Work and the Standards That Govern Them

When a fire occurs, a sprinkler system can only perform as well as the water supply behind it. In many commercial, industrial, and high-risk buildings, a dedicated fire pump is installed to ensure that sufficient water pressure and flow are available when the sprinkler system operates.

Fire pumps are one of the most critical components within any fire protection system. Their sole purpose is to provide reliable water delivery when it matters most, helping to control or extinguish a fire before it can spread and cause significant damage.

In this article, we'll explain what electric and diesel fire pumps are, how they operate, how they are initiated during a fire event, and the common standards used throughout the UK fire protection industry.

What Is a Fire Pump?

A fire pump is a specialist pump designed to increase the pressure and flow of water supplied to a fire sprinkler system.

In many buildings, the incoming water supply is unable to provide the required pressure or flow needed to protect the entire premises. The fire pump bridges this gap by taking water from a storage tank, reservoir, or mains supply and delivering it to the sprinkler system at the pressure required by the design specification.

Unlike many industrial pumps, fire pumps remain on standby for most of their life. They may not run for months at a time, but when required they must start immediately and operate reliably throughout a fire emergency.

This is why fire pumps are built and maintained to exceptionally high standards.

Why Are Fire Pumps Installed?

Fire pumps are installed where:

• Water pressure from the mains supply is insufficient.
• Large buildings require higher flow rates.
• High-rise structures need additional pressure.
• Warehouses require specialist sprinkler protection.
• Insurance requirements specify dedicated fire protection systems.
• Business continuity is critical.

Without a correctly operating fire pump, the sprinkler system may not receive sufficient water to control a fire effectively.

The Typical Components of a Fire Pump Installation

A fire pump installation usually consists of:

Fire Pump

The main pump responsible for delivering water to the sprinkler system.

Driver

The power source that drives the pump.

This may be:

• An electric motor
• A diesel engine

Jockey Pump

A smaller pump used to maintain system pressure and prevent unnecessary operation of the main fire pump.

Controller

The control panel that monitors system pressure and automatically starts the fire pump when required.

Water Storage Tank

Provides a dedicated water supply for firefighting purposes.

Pipework and Valves

Direct water from the storage tank to the sprinkler system.

What Is an Electric Fire Pump?

An electric fire pump uses an electric motor to drive the pump.

These systems are commonly installed where a reliable electrical supply is available and where the risk assessment allows an electrically driven pump.

Electric pumps are popular because they:

• Require less maintenance than diesel units.
• Produce no exhaust emissions.
• Operate quietly.
• Have fewer moving parts.
• Are generally simpler to operate.

Electric fire pumps can range from relatively small installations to large industrial systems delivering thousands of litres per minute.

How Does an Electric Fire Pump Start?

The fire pump controller continuously monitors sprinkler system pressure.

Under normal conditions, the system remains fully pressurised.

When a sprinkler head operates due to heat from a fire:

1. Water begins flowing through the activated sprinkler.
2. System pressure starts to drop.
3. The jockey pump may start first to restore pressure.
4. If pressure continues to fall below a predetermined set point, the fire pump controller receives a start signal.
5. The electric motor starts automatically.
6. The fire pump delivers water at the required pressure and flow rate.

One important feature of fire pump systems is that they are generally designed to continue running once started.

Unlike many industrial pumps, they are not intended to stop automatically once pressure recovers. This prevents accidental shutdown during an active fire situation.

What Is a Diesel Fire Pump?

A diesel fire pump uses a diesel engine instead of an electric motor.

These pumps are often installed as either:

• The primary fire pump.
• A standby fire pump.
• Part of a dual-pump arrangement.

Diesel pumps provide an independent source of power and are particularly valuable if the electrical supply fails during a fire.

Many insurers and high-risk facilities favour diesel fire pumps because they continue operating even during complete power outages.

How Does a Diesel Fire Pump Start?

The initiation process is very similar to an electric fire pump.

When sprinkler system pressure falls:

1. The fire pump controller detects the pressure drop.
2. A start signal is issued.
3. The diesel controller energises the starting circuit.
4. The diesel engine cranks using dedicated batteries.
5. The engine starts and accelerates to operating speed.
6. The pump begins supplying water to the sprinkler system.

Most diesel fire pumps are equipped with:

• Dual starting batteries.
• Battery chargers.
• Engine monitoring systems.
• Cooling systems.
• Fuel tanks sized to meet standard requirements.

The dual battery arrangement ensures maximum reliability should one battery fail.

Why Is a Jockey Pump Used?

A common misconception is that the fire pump starts every time pressure drops slightly.

In reality, this would cause excessive wear and unnecessary operation.

The jockey pump maintains normal system pressure by compensating for:

• Minor leaks.
• Temperature fluctuations.
• Small pressure losses.

Only when the pressure falls beyond the jockey pump's capability will the main fire pump start.

Understanding LPCB Fire Pump Systems

In the UK, one of the most recognised standards is LPCB.

LPCB stands for:

Loss Prevention Certification Board

LPCB-approved systems are designed and installed in accordance with standards published by the fire protection industry and are widely accepted by insurers throughout the UK and Europe.

LPCB systems typically follow the requirements of:

BS EN 12845

and

LPC Rules for Automatic Sprinkler Installations

These standards cover:

• Pump performance
• Water supplies
• Installation requirements
• Pump house construction
• Testing procedures
• Maintenance requirements
• Reliability criteria

LPCB approval provides confidence that equipment has been independently tested and meets recognised fire protection standards.

Understanding FM Approved Fire Pump Systems

FM stands for:

Factory Mutual

FM Global is one of the world's largest commercial property insurers and has developed its own engineering standards for fire protection systems.

FM Approved equipment undergoes extensive testing to demonstrate reliability and performance.

FM standards are commonly found in:

• Distribution centres
• Manufacturing facilities
• Data centres
• Logistics operations
• Large industrial sites

Many multinational organisations specify FM Approved systems because they align with insurance requirements and global engineering standards.

LPCB vs FM – What's the Difference?

Both standards aim to achieve the same goal:

Providing a reliable water supply during a fire.

However, there are differences in design philosophy, testing methods, and installation requirements.

Generally speaking:

LPCB

• Common throughout the UK and Europe.
• Often based around BS EN 12845 requirements.
• Widely accepted by UK insurers.
• Frequently specified on commercial projects.

FM

• Common within multinational organisations.
• Often specified by FM Global insured sites.
• Includes its own approval processes and engineering standards.
• Frequently found on large industrial and logistics facilities.

Neither system is necessarily "better" than the other. The correct choice is normally determined by the building's insurance requirements, fire risk assessment, and project specification.

Why Regular Maintenance Is Essential

A fire pump may spend years waiting for an emergency.

The challenge is ensuring it performs perfectly when needed.

Routine maintenance helps identify:

• Battery issues.
• Cooling system faults.
• Fuel system problems.
• Electrical faults.
• Pressure switch issues.
• Controller faults.
• Pump wear and seal degradation.

Weekly, monthly, quarterly, and annual inspections form an essential part of ensuring ongoing compliance and system reliability.

Final Thoughts

Fire pumps are the heart of any sprinkler system. Whether driven by an electric motor or a diesel engine, their purpose remains the same: to provide a reliable supply of water during a fire emergency.

Understanding how these systems operate and the standards that govern them is essential for building owners, facilities managers, insurers, and engineers alike.

At Fire Pump & Generator Spares, we understand the importance of keeping these critical systems operational. With over 20 years of hands-on experience working on fire pumps, diesel engines, generators, controllers, and associated equipment, our goal is to help engineers source the parts, technical information, and support they need to keep life safety systems performing as intended.

Because when a fire pump is needed, failure is not an option.