What is a Fire Hydrant?

Sheri Cyprus

A fire hydrant is a pipe that allows water to flow from a water main with the control of a valve in order to put out a fire. Above-ground fire hydrants originated in the 1800s, but the underground type was used in Asia and Europe as far back as the 1700s. In the United States, a hydrant may also be called a "fire plug" or a "Johnny pump," depending on the region.

Firefighters connect fire hoses to fire hydrant to provide them with water to put out flames.
Firefighters connect fire hoses to fire hydrant to provide them with water to put out flames.

Before the invention of the fire hydrant, firefighters used the bucket brigade or hand pumping systems, of getting water to put out fires. A hole had to be dug in order to retrieve water from the water main and firefighters would pass buckets of water from the hole along a line of firefighters to help get water to the fire. Since the newly dug holes had to be plugged up after the fire call, the term "fire plugs" began to be used.

Before fire hydrants became available, firefighters used hand pumps and buckets to put out blazes.
Before fire hydrants became available, firefighters used hand pumps and buckets to put out blazes.

A firefighter connects a fire hose to the hydrant and releases a valve to get water from the water main. The different valves on a fire hydrant allow it to be attached to different water sources that may be either pressurized or not pressurized. Most hydrants are designed to allow not less than 250 gallons (950 liters) of water to flow through the hydrant per minute.

Many different patents were used to create various fire hydrants. Wooden outer encasements were used before the more familiar cast iron cover commonly seen today. The American Water Works Association (AWWA) regulates the design of hydrants in the United States to meet fire district standards.

Dry barrel and wet barrel are the two kinds of fire hydrants. The wet barrel type holds a constant water supply, while the dry barrel type needs to have a valve release to let water in. The main benefit of a dry barrel hydrant is that its design avoids a frozen water supply in very cold climates. Some wet barreled hydrants may be made of bronze rather than iron, or they may have an inside finish that avoids rusting.

The barrel of a fire hydrant may also be known as a "standpipe." Some are rounded in style, while others have more angular lines. The outlets on a hydrant are usually made of bronze, but the caps may be made from other types of metal.

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Discussion Comments


All fire hydrants I've ever seen are bright, easy to see colors, like lemon yellow. I once saw a purple fire hydrant, too! I think they're painted this way to be easy for fire engines to find. I wonder why the fire hydrants aren't painted red to match most fire engines, though? It would make sense to me.


If anyone does have a fire hydrant on your personal property, make sure you check out who is responsible for its maintenance. Often the city is automatically responsible, but sometimes due to bylaws it becomes the homeowners job to make sure it is working. Though in this case, you can usually get any costs associated with upkeep reimbursed by your city.

Fire hydrants needs to be flushed out at least twice a year to make sure the pipes are free of debris and to check to make sure it is functioning properly. Also, the area around the fire hydrant must be kept clear at all times.


If you have a fire hydrant in front of your house you should be aware that there are some laws that revolve around parking near it. Usually cities will have a bylaw in place that says you must park at least 3 meters (or around 10 feet) away from the hydrant at all times. This allows fire fighters to have access to your hydrant in case of an emergency.

If you do park near the fire hydrant, getting a costly fine or being towed are likely. It is best to check your local bylaws if you have a fire hydrant on your property.

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