Fire hydrants allow water to flow from a mains supply to put out fires. They originated in the 1800s and replaced hand pump systems. Different types of hydrants exist, including wet and dry barrel, and they are regulated by the American Water Works Association.
A fire hydrant is a pipe that allows water to flow from a mains water supply with the control of a valve to put out a fire. Above-ground fire hydrants originated in the 1800s, but the underground type was used in Asia and Europe as early as the 1700s. In the United States, a fire hydrant may also be called a “fire cap” or a “Johnny pump,” depending on the region.
Before the invention of the fire hydrant, firefighters used grab or hand pump systems to get water to put out fires. A hole had to be dug to retrieve water from the water main and firefighters would pass buckets of water from the hole along a line of firefighters to help bring water to the fire. Since newly dug holes had to be plugged after the call to fire, the term “fire plugs” began to be used.
A firefighter attaches a fire hose to the hydrant and releases a valve to draw water from the mains water supply. The different valves on a fire hydrant allow it to be connected to different water sources which can be pressurized or non-pressurized. Most fire hydrants are designed to allow no less than 250 gallons (950 liters) to flow through the hydrant per minute.
Many different patents have been used to create various fire hydrants. Wood outer shells were used before the more familiar cast iron roofing commonly seen today. The American Water Works Association (AWWA) regulates fire hydrant design in the United States to meet fire district standards.
Dry barrel and wet barrel are the two types of fire hydrants. The wet-barrel type maintains a constant water supply, while the dry-barrel type must have a release valve to let the water in. The primary advantage of a dry barrel fire hydrant is that its design avoids an ice cold water supply in very cold climates. Some wet barrel fire hydrants may be made of bronze rather than iron, or may have an internal finish that prevents rust.
The barrel of a fire hydrant may also be known as a “standpipe”. Some have a rounded style, while others have more angular lines. The outlets on a fire hydrant are usually made of bronze, but the caps can be made of other types of metal.
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