What Is a Fire Hydrant?
A fire hydrant is a pipe connected to a main water supply. A valve controls the flow of water through the hydrant.
Firefighters connect a fire hose to the hydrant during an emergency. The hydrant then supplies water for firefighting operations.
A fire hydrant protection system is designed to control large fires. It can be used in buildings and areas with different levels of fire risk.
The system is also designed to remain operational even when part of the affected structure is damaged or collapses.
Dry Barrel Fire Hydrant
A dry barrel fire hydrant is commonly installed in cold regions. It is suitable for places where temperatures may fall below the freezing point of water.
The main water valve is installed below the frost line. This keeps the water supply underground and reduces the risk of freezing.
Dry barrel hydrants are available with several operating mechanisms, including:
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Slide-gate mechanisms
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Toggle mechanisms
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Compression mechanisms
After the hydrant is used, water drains out of the barrel. Therefore, no water remains inside the hydrant.
This design helps prevent freezing and damage caused by frost.
When firefighters use the hydrant, they first connect a hose to the outlet. They then open the operating valve at the top.
The main valve opens and allows water to enter the hydrant. At the same time, the drain valve closes.
Water then flows through the hydrant and into the fire hose.
Wet Barrel Fire Hydrant
A wet barrel fire hydrant is commonly used in areas with warm climates. Water remains inside the hydrant barrel at all times.
Each outlet has its own valve. Firefighters can connect a fire hose directly to the required outlet.
The outlet valves operate independently. This allows firefighters to control each outlet separately.
Most mechanical parts are located above ground. As a result, inspection, adjustment and repair work are easier to carry out.
Differences Between Dry Barrel and Wet Barrel Fire Hydrants
| Dry Barrel Fire Hydrant | Wet Barrel Fire Hydrant |
|---|---|
| Used in cold regions where temperatures may fall below freezing. | Used in warmer climates. |
| Water is kept below ground to prevent freezing. | Water remains inside the barrel above ground. |
| More complex and expensive to install. | Simpler and less expensive to install. |
| Maintenance can be more difficult because some components are underground. | Maintenance is easier because most components are above ground. |
Fire Hydrant Colour Codes
NFPA 291 provides colour-coding guidance for fire hydrants. The colours help firefighters identify the approximate water flow available from a hydrant.
However, the colour code is only a guideline. Local authorities and water service providers may use different colour systems.
| Colour | Hydrant Class | Flow Rate |
|---|---|---|
| Red | Class C | Less than 500 gallons per minute |
| Yellow | Class B | 500 to 999 gallons per minute |
| Green | Class A | 1,000 to 1,499 gallons per minute |
| Dark blue | Class AA | 1,500 gallons per minute or more |
What Are Fire Hydrants Used For?
1. Firefighting
Fire hydrants provide a reliable water supply during firefighting operations.
Firefighters connect their hoses to the hydrant and use the water to control or extinguish a fire.
2. Water-Line Flushing
Fire hydrants can release a large volume of water in a short time.
This makes them useful for removing sediment, dirt and other materials from water lines.
3. System Testing
Fire hydrants can be used to test the hydraulic performance of a water distribution system.
The test helps measure water pressure and flow capacity.
4. Construction and Cleaning Work
Fire hydrants may also be used as a temporary water source for approved activities, such as:
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Commercial construction
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Sewer cleaning
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Road construction
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Street cleaning
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Public maintenance work
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