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Indian Standards IS 15105 : 2021

Design, Installation and Maintenance of Fixed Automatic Sprinkler System

IS 15105:2021 is the Indian Standard issued by the Bureau of Indian Standards (BIS) that specifies the minimum requirements for the design, installation, and maintenance of fixed automatic sprinkler systems in buildings.

This standard applies to sprinkler systems used for the protection of life and property across a wide range of occupancies, including industrial, commercial, residential, and storage buildings.

Scope of the Standard

The standard covers:

  • Design criteria for sprinkler systems

  • Installation requirements

  • Hydraulic calculation methods

  • Water supply and pumping capacity requirements

  • Hazard classification of occupancies

  • Storage commodity categorization

  • Requirements for high-rise buildings

  • Guidelines for ESFR, Large Drop, and in-rack sprinklers

  • Documentation and drawing requirements

  • Maintenance provisions to ensure system reliability

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The provisions are applicable to:

  • New installations

  • Additions or extensions to existing sprinkler systems

  • Modifications or repairs to installed systems

What is NOT Covered

This standard does not apply to:

  • Water spray systems

  • Deluge systems (covered under IS 15325 and IS 15519)

  • Marine, aircraft, vehicle or mining sprinkler applications

Design Philosophy

IS 15105 emphasizes:

  • Proper hazard classification (Light, Ordinary, High, Storage)

  • Hydraulic calculation for high hazard systems

  • Enhanced storage protection requirements

  • Adoption of modern sprinkler technologies such as ESFR

  • Integration of sprinkler systems with overall fire protection strategy

The 2021 revision strengthens hydraulic design requirements and aligns Indian practice closer to international standards.

🔥 Types of Sprinklers

Types of Sprinkler.png

Alarm Valve

An alarm valve is a specially designed check valve installed in a sprinkler system that allows water to flow into the system when a sprinkler operates and simultaneously initiates an alarm signal.

When water flows through the valve due to sprinkler activation, it operates an alarm device such as:

  • A water motor gong (mechanical alarm), and/or

  • An electric pressure switch connected to the fire alarm system.

Each type of sprinkler system (wet, dry, deluge, pre-action) incorporates a suitable alarm valve arrangement to ensure that water flow during fire conditions is automatically detected and signaled.

The alarm valve also permits system monitoring through upstream and downstream pressure gauges and includes provisions for alarm testing.

Alarm Valve.png

Main Elements of a Sprinkler Installation

FIG 1.png

🔹 Key Components

  • Installation Control Valve Set
    Includes the alarm valve and stop valve. It controls water supply to the sprinkler system and initiates alarm when water flows.

  • Main Distribution Pipe (Feed Main)
    Primary pipe that distributes water to different distribution pipes.

  • Distribution Pipe (Cross Main / Destination Pipe)
    Supplies water to branch (range) pipes.

  • Range Pipe (Branch Pipe)
    Pipes feeding individual sprinklers directly or through arm pipes.

  • Arm Pipe
    Short pipe (generally less than 300 mm) connecting range pipe to sprinkler head.

  • Riser
    Vertical pipe supplying water to upper levels.

  • Sprinkler Head
    Heat-activated device that discharges water when fire is detected.

  • Design Point
    Reference point used in hydraulic calculations (especially in pre-calculated systems).

  • Drain Valve with Plug
    Used for draining and testing the system.

🔹 Working Principle (Simple Flow Path)

Water Supply → Control Valve Set → Main Distribution Pipe → Distribution Pipe → Range Pipe → Sprinkler Head

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When a sprinkler operates, water flows through the alarm valve, triggering an alarm.

Range Pipe Arrays in Sprinkler Systems

The figure shows different configurations of range (branch) pipes connected to distribution pipes in a sprinkler installation. These layouts affect hydraulic performance and water distribution.

FIG 2.png

1️⃣ End-Side Array (Central Feed)

  • Range pipes provided on one side only of the distribution pipe.

  • Water fed from central point.

  • Used in narrow areas or where layout is restricted.

​

2️⃣ End-Side Array (End Feed)

  • Range pipes on one side.

  • Water supply connected at one end of distribution pipe.

  • Simpler layout but higher friction loss at far end.

​

3️⃣ End-Centre Array (Central Feed)

  • Range pipes on both sides of distribution pipe.

  • Supply from centre.

  • More hydraulically balanced.

  • Common in large open floor areas.

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4️⃣ End-Centre Array (End Feed)

  • Range pipes on both sides.

  • Supply from one end.

  • Requires careful hydraulic calculation for pressure drop.

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Engineering Importance

  • Layout selection impacts:

    • Hydraulic calculations

    • Pressure loss

    • Number of operating sprinklers

    • Design area performance

  • End feed systems generally require higher pressure at remote points.

  • Central feed systems provide better pressure balance.

Sprinkler Network Layouts

This figure illustrates different sprinkler spacing patterns and piping network arrangements used in sprinkler system design.

FIG 3 - 3A.png

3A – Rectangular Matrix Layout

  • Sprinklers arranged in straight rows and columns.

  • Equal spacing in both directions.

  • Most commonly used layout.

  • Easy for hydraulic calculations.

  • Suitable for standard hazard occupancies.

S = Distance between sprinklers in one direction
D = Distance between sprinklers in the other direction

FIG 3 - 3C.png

3C – Looped Layout

  • Cross mains interconnected.

  • Water can reach sprinklers from more than one direction.

  • Reduces pressure loss.

  • More hydraulically reliable than simple tree systems.

FIG 3 - 3B.png

3B – Staggered Layout

  • Alternate rows offset by half spacing.

  • Provides more uniform water distribution.

  • Improves coverage efficiency.

  • Often used where better spray overlap is required.

FIG 3 - 3D.png

3D – Gridded Layout

  • Branch lines interconnected forming grid pattern.

  • Water supplied from multiple paths.

  • Provides best hydraulic balance.

  • Suitable for large floor plates and high hazard areas.

Engineering Significance

FIG 3 Significance.png

Requirements Regarding Documentation

IS 15105 specifies that proper drawings and documentation must be submitted for approval before installation of a sprinkler system.

General Drawing Requirements

  • Drawings must be clear, dated, and to scale.

  • Scale generally: 1:500 or 1:1000 (site plans).

  • For installation layout: not less than 1:100.

  • Digital copies are acceptable if approved.

  • Drawings must show:

    • Entire compound

    • All buildings

    • Future extensions (if any)

    • Boundary walls

Details to be Shown on Drawings

Building Information

  • Fire walls, fire doors, shutters

  • Construction type (masonry, steel, etc.)

  • Floor areas and elevations

  • Ceiling heights

  • Concealed spaces

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Sprinkler System Details

  • Complete sprinkler layout

  • Pipe sizes and routing

  • Type of sprinklers

  • Temperature rating

  • K-factor

  • Number of sprinklers per control valve

  • Height of highest sprinkler

  • Location of alarm valves

  • Drain valves and test valves

​

Water Supply Details

  • Pump capacity and head

  • Pump house layout

  • Suction and delivery piping

  • Water tank capacity and compartmentation

  • Overflow and freeboard levels

  • Electrical supply to fire pumps

Hydraulic Calculation Requirements

For Fully Hydraulic Systems, documentation must include:

  • Design density (mm/min)

  • Design area (m²)

  • Assumed Maximum Area of Operation (AMAO)

  • Sprinkler K-factor

  • Flow through each sprinkler

  • Pressure at each node

  • Pipe sizes

  • Pipe lengths

  • Equivalent lengths of fittings

  • Hazen-Williams coefficient

  • Static head changes

  • Friction loss calculations

  • Pressure-flow graph of water supply

Mandatory Declaration

A statement confirming:

The system complies with IS 15105:2021, including any deviations with justification.

Why Documentation is Important

  • Ensures regulatory approval

  • Verifies hydraulic balance

  • Confirms adequate water supply

  • Provides reference for maintenance

  • Prevents under-designed systems

Classification of Occupancies

The sprinkler system design depends on the fire load, combustibility, and fire growth potential of the occupancy. IS 15105 classifies occupancies into four main categories.

Classification of Occupancies – Typical Examples

Classification of Occupancies - Examples.png

Storage Hazards

Storage Hazards.png

PLANNING STAGE

The planning stage ensures proper integration of the sprinkler system with building design, water supply, and other fire protection measures.

1️⃣ Initial Considerations

Planning1.png

2️⃣ Outline Design Considerations

Planning2.png

3️⃣ Interaction with Other Fire Protection Systems

Planning3.png

4️⃣ Extent of Sprinkler Protection

Planning4.png

5️⃣ Exceptions (Where Sprinklers May Not Be Required)

Planning5.png

Planning Stage – Key Objective

✔ Correct hazard classification
✔ Adequate water supply
✔ Proper integration with building design
✔ Avoid conflicts with other fire systems
✔ Ensure long-term maintainability

Protection of Concealed Spaces

Protection of Concealed Spaces.png

Height Difference Between Highest & Lowest Sprinklers

Height Difference Between Highest & Lowest Sprinklers.png

SPRINKLERS – General Requirements

1️⃣ General Provisions

General Provisions.png

2️⃣ Selection of Sprinklers

Sprinklers shall be selected based on:

  • Occupancy hazard classification

  • Storage configuration (if applicable)

  • Ceiling height

  • Type of sprinkler system (wet, dry, etc.)

  • K-factor requirements

  • Temperature rating

3️⃣ Installation Requirements

  • Sprinklers must be installed in correct orientation (pendent/upright/sidewall).

  • Installed as per spacing and positioning rules of the standard.

  • Must comply with approved listing and manufacturing standards.

  • Only listed sprinklers for special applications (e.g., concealed spaces) shall be used.

4️⃣ K-Factor Requirement

K-factor.png
Table-1.png
Table - 2.png

Selection of Temperature Rating for Sprinklers

Sprinklers operate when the thermal element reaches its rated temperature. The correct temperature rating must be selected based on the maximum expected ambient ceiling temperature.

Table 3 and 4.png

Typical Selection Guidance

Typical Selection Guidance.png

Temperature Rating for High Piled Storage

1️⃣ High Hazard – High Piled Storage

High Hazard – High Piled Storage.png

2️⃣ Glazed Roof or PVC / Plastic Roofing Sheets

Glazed Roof or PVC.png

3️⃣ Near Ovens or Hot Process Hoods

Near Ovens.png

4️⃣ Clearance from Hot Sources

Because sprinklers are heat sensitive:

  • Must be located minimum 750 mm to 2000 mm away from hot sources

  • Distance depends on ambient temperature conditions

🔥 Key Engineering Insight

High piled storage produces:

  • Rapid fire growth

  • High ceiling jet temperatures

Therefore:
✔ Higher temperature rating prevents premature activation
✔ Ensures correct sequence of sprinkler operation
✔ Avoids unnecessary system discharge

Mixing of Different Types of Sprinklers

🔹 General Rule

Different types of sprinklers shall not be used in the same hazard area, unless specifically justified and approved.

Mixing different sprinkler characteristics can result in:

  • Uneven water distribution

  • Hydraulic imbalance

  • Improper fire control performance

🔹 The Following Shall Be Avoided

The Following Shall Be Avoided.png

🔥 Engineering Principle

A sprinkler system must operate as a uniform hydraulic and thermal unit.
Mixing types within the same hazard area may cause:

  • Delayed suppression

  • Over-discharge in some areas

  • Under-protection in remote areas

Protection to the Sprinklers

🔹 General Requirement

Sprinklers shall be installed and protected so that their operation, discharge pattern, and sensitivity are not impaired by mechanical damage, corrosion, or environmental conditions.

🔹 Mechanical Protection

Mechanical Protection.png

🔹 Corrosion Protection

Corrosion Protection.png

🔹 Installation Protection

  • Sprinklers shall not be obstructed.

  • Guards or protective devices shall not interfere with water distribution.

  • Only manufacturer-approved protective devices shall be used.

🔥 Objective of Clause 7.9

✔ Ensure sprinkler reliability
✔ Prevent accidental damage
✔ Maintain proper spray performance
✔ Preserve thermal sensitivity

Spare Sprinklers to be Kept in Stock

A stock of spare sprinkler heads shall be maintained on the premises to enable prompt replacement of operated or damaged sprinklers.

Storage Requirements.png
Table - 5.png
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