A fire hydrant is a water pipe used to extinguish fires or supply water for firefighting purposes. Fire hydrants are usually found near fire stations and other public areas. There are different types of fire hydrants, but all have a few things in common: they provide water to put out fires, and they are connected to a water main. They are designed to provide water for firefighting under high pressure.
Types of Fire Hydrants
There are different kinds of fire hydrants. Let’s take a look at some of them.
Wet Barrel Hydrant
Wet hydrants are the most common type. They have a valve at the top that is used to open and close the water flow. There is also a lever located near the ground that is used to open and close the hydrant’s nozzle. This type of hydrant usually has a flat-faced spigot on the side, which is what firefighters use to attach their hoses.
Wet barrel hydrants are usually made of cast iron and they can be either painted red or left their natural color.
Dry Barrel Hydrant
Dry barrel hydrants don’t have a valve at the top. The water flow is controlled by a screw-on cap that is located on the top of the barrel. This type of hydrant usually has a threaded spigot on the side, which is what firefighters use to attach their hoses.
Dry barrel hydrants are made of either cast iron or plastic and they come in different colors, including red, green, and yellow.
Dry barrel hydrants are available in three varieties: slide-gate, toggle, and compression mechanisms.
- Slide-Gate Mechanism
The slide-gate mechanism is the most common type of dry barrel hydrant. The gate valve is located on the side of the barrel and it slides open to allow water to flow into the barrel. When the firefighters are done using the hydrant, they close the gate valve to stop the water from flowing out.
- Toggle Mechanism
The toggle mechanism is also a common type of dry barrel hydrant. The difference between the toggle and slide-gate mechanisms is that the toggle has a lever instead of a gate valve. This lever is located on the top of the barrel and is used to open and close the water flow.
- Compression Mechanism
The compression mechanism is the least common type of dry barrel hydrant. It is used in areas where there is a lot of sediment or grit in the water. The compression mechanism has a plunger that pushes down on the water to create a seal and stop the flow of water.
Other Purposes and Uses of Fire Hydrant
Fire hydrant’s main reason for existing is for firefighters to have a quick and easy way to access water while fighting fires, but there are other purposes and uses for fire hydrants as well. Some of them are:
Testing System
The hydraulic capacity of the distribution system can be tested by opening the hydrant and measuring the rate of flow. The time it takes to fill a certain container gives an indication of how much water is available in the system.
Line Flushing
Hydrants are also used for flushing purposes. By opening them up, debris and sediment can be flushed from the distribution lines. This helps to maintain a good flow of water and keeps the system functioning properly.
Lawn Irrigation
One unusual use for fire hydrants is to provide irrigation for lawns. In areas where there is a shortage of water, some homeowners have been known to hook up hoses to the hydrant in order to get supplemental watering for their yards.
Parts of a Fire Hydrant
There are several parts to a fire hydrant. Here is a brief description of each:
Valves
The valves are used to control the flow of water. There are two main valves – the inlet valve and the outlet valve. The inlet valve is located on the top of the hydrant and it controls the flow of water into the hydrant. The outlet valve is located at the bottom of the hydrant and it controls the flow of water out of the hydrant.
Stem Nut
The stem nut is the part of the hydrant that holds the valves in place.
Bonnet
The bonnet is the top of the hydrant. It is the cap that covers and protects the valves. Within the bonnet are the stem nut. It prevents water from penetrating the hydrant and keeps out dirt and other debris.
Flow Restrictor
The flow restrictor is a small disk located in the outlet valve. It restricts the flow of water so that it doesn’t exceed the safe operating pressure for the fire department hose connections.
Spigot
The spigot is the outlet of the hydrant. It is the part that connects to the hose. The spigot has a threaded end that screws into the water main.
Outlets
The outlets are the openings on the side of the hydrant where the water comes out. There are usually two or three outlets on a fire hydrant.
Flange
The flange is the metal ring that attaches the hydrant to the ground. It has holes in it for attaching the bolts that hold the hydrant in place.
Hydrant’s Color-Coding
There are colors assigned to each type of fire hydrant. This makes it easier for firefighters to identify the correct hydrant when they are fighting a fire. The colors also help with fire hydrant maintenance, so workers know which hydrants need repairs or replacement parts.
Red Bonnet Fire Hydrant
A hydrant that contains 500 gallons per minute (GPM) of water or less. This type of hydrant is usually found in rural areas.
Orange Bonnet Fire Hydrant
A hydrant that contains at least 1000 GPM of water. This type of hydrant is usually found in suburban or urban areas.
Green Bonnet Fire Hydrant
Contains 1,500 GPM of water or more. This type of hydrant is usually found near high-density areas, such as schools or hospitals.
Blue Bonnet Fire Hydrant
Contains more than 1,500 GPM of water. This type of hydrant is usually found near industrial areas.
Fire Hydrant Flow Rates
The amount of water a fire hydrant can deliver is measured in gallons per minute (GPM). The flow rate will vary depending on the type of hydrant and the water pressure in the area. Firefighters use a tool called a fire hydrant meter to measure the flow rate. This information is important when designing a fire suppression system for a building or choosing which hydrants to connect to a water supply line.
Conclusion
A fire hydrant might seem simple to look at, but there is a lot of information that firefighters need to know in order to use them effectively. Understanding the different types of fire hydrants and their flow rates can help you be better prepared in case of a fire.