Fire Water Tank and Fire Piping Requirements

With the rapid urbanization process in developing countries and the increasing renovation demand for aging buildings and infrastructure in developed countries, the requirements for building fire safety and infrastructure upgrades continue to grow. A reliable and stable fire water storage system has become an essential component of modern building fire protection systems.

As a key water storage facility in fire protection systems, fire water tanks must not only meet capacity and safety requirements but also provide excellent corrosion resistance, easy installation, and long-term operational stability. Among various types of fire water tanks, hot-dip galvanized fire water tanks have become a widely adopted solution for global building fire protection, pump and valve systems, and engineering projects due to their excellent corrosion resistance, long service life, modular installation advantages, and cost-effectiveness.

In addition to the tank material itself, the compatibility of connection sizes and piping standards is also a common concern during the procurement and installation of fire water tanks. Different countries and regions adopt different fire protection codes, piping standards, and flange specifications. Correct selection of inlet, outlet, overflow, and other connection sizes is essential to ensure the safe and reliable operation of the fire protection system.

The following section introduces common fire water tank connections and related standard requirements.

1. Fire Water Tank Connection Requirements

1.1 Inlet Pipe

Item	Chinese Standard Requirements	Common International Practice
Minimum Diameter	≥ DN32	Usually determined according to make-up water flow requirements
Design Requirement	The pipe size should ensure that the fire water tank can be fully refilled within the specified time (such as 8 hours)	Determined based on the water supply capacity of the fire protection system
Control Method	Float valve or level control valve is recommended	Float valves and automatic level control valves are commonly used

Notes:

The inlet pipe is generally not the key pipe affecting fire water supply capacity, and its diameter is usually smaller than the outlet pipe.

Common configurations:

• Small tanks: DN50
• Medium tanks: DN65–DN100
• Large tanks: DN100–DN150

1.2 Fire Water Outlet Pipe

Item	Chinese Standard Requirements	Common International Practice
Minimum Diameter	≥ DN100	Usually DN100–DN200
Function	Connects to the fire piping network to provide emergency water supply	Connects to fire pumps, fire risers, or fire loops
Anti-vortex Requirement	Sufficient submergence depth is required	NFPA 22 also requires measures to prevent air entrainment

Common International Project Applications:

Building Type	Common Outlet Size
Small Buildings	DN100
Commercial Buildings	DN100–DN150
Factories and Warehouses	DN150
Large Fire Protection Systems	DN200 or larger

Recommended Outlet Design for Modular Fire Water Tanks:

Outlet size: DN100 / DN150

Among them, DN150 is commonly used for large-scale international fire protection projects.

1.3 Overflow Pipe

Item	Requirement
Minimum Diameter	≥ DN100
Diameter Relationship	Not less than twice the diameter of the inlet pipe
Function	Prevents water overflow when the tank is full

Common international practice:

• Overflow pipe: DN100–DN200
• Discharge direction should avoid affecting equipment and building structures.

2. Outdoor Fire Water Piping Requirements

Outdoor Fire Main

Item	Chinese Standard	Common International Standard
Minimum Diameter	DN100	DN100 (4 inch)
Recommended Size	DN150	DN150 (6 inch) commonly used
Pipeline Layout	Ring network preferred	NFPA recommends looped systems for higher reliability

Common international fire main sizes:

• DN100 (4″)
• DN150 (6″)
• DN200 (8″)

Large industrial projects such as factories, warehouses, and airports may use:

• DN250
• DN300

3. Indoor Fire Piping Requirements

Indoor Fire Main System

Pipeline Layout

Chinese requirements:

• Ring piping systems are preferred.
• Reliable water supply arrangements are required for systems equipped with elevated fire water tanks.

International standards such as:

• NFPA 14 (Standpipe Systems)
• NFPA 13 (Automatic Sprinkler Systems)

also emphasize:

• Reliable main piping systems
• Loop water supply arrangements
• Prevention of single-point failures

Pipe Flow Velocity Requirements

Item	Chinese Requirement	International Practice
Recommended Velocity	≤ 2.5 m/s	Usually around 2–5 m/s
Maximum Velocity	≤ 7 m/s	Limited according to system pressure and design requirements

4. Fire Pipe Connection Methods

International fire protection projects mainly use the following connection methods:

1. Grooved Coupling

Applications:

• Fire sprinkler systems
• Indoor fire piping systems

Advantages:

• Fast installation
• Easy maintenance
• Provides certain flexibility

2. Flanged Connection

Commonly used for:

• Fire water tank connections
• Fire pump connections
• Large diameter pipelines

3. Flexible Coupling

Suitable for:

• Underground pipelines
• Areas with vibration equipment
• Pump room connections

5. Typical Fire Water Tank Connection Configuration (International Reference)

Connection	Recommended Size
Inlet	DN50–DN100
Fire Water Outlet	DN100–DN150
Overflow	DN100–DN150
Drain	DN50–DN100
Vent	DN50–DN100
Manhole	DN600

6. Comparison Between Chinese and International Standards

Item	Chinese GB Standards	International NFPA / EN Standards
Fire Water Tank Outlet	≥ DN100	Usually DN100–DN200
Outdoor Fire Main	≥ DN100, DN150 recommended	4″–6″ commonly used
Indoor Fire Piping	Ring system preferred	Ring system preferred
Pipe Connection	Flange, grooved, flexible coupling	Grooved and flange connections widely used
Anti-vortex Requirement	Clearly specified	Also emphasized in NFPA 22
Connection Size System	DN system	DN / NPS inch system

As one of China’s leading modular water tank manufacturers, we have extensive project experience and provide one-stop fire water tank solutions, including system design, customized structure, connection configuration, manufacturing, and installation guidance.

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