During my walks, I see fire hydrants — sometimes in unusual places. This one was in a plaza midway between a restaurant’s outdoor patio and a five-story apartment complex.
According to Wikipedia, before piped mains, water for firefighting had to be kept in buckets and cauldrons ready for use by “bucket-brigades” or brought with a horse-drawn fire-pump. From the 16th century, as wooden mains water systems were installed, firefighters would dig down the pipes and drill a hole for water to fill a “wet well” for the buckets or pumps. It had to be filled and plugged afterwards, hence the common U.S. term for a hydrant — fireplug. A marker would be left to indicate where a “plug” had already been drilled to enable firefighters to find ready-drilled holes. Later, wooden systems had pre-drilled holes and plugs.
When cast-iron pipes replaced the wood, permanent underground access points were included for the firefighters. Some countries provide access covers to these points, while others attach fixed above-ground hydrants — the first cast iron ones patented in 1801 by Frederick Graff, then chief engineer of the Philadelphia Water Works.
In 1896, during a terrible heat wave in New York City, Chief of Police Theodore Roosevelt ordered the opening of the fire hydrants to provide relief to the population. Today, some U.S. communities provide low-flow sprinkler heads to enable residents to use the hydrants to cool off during hot weather, while gaining some control on water usage. Sometimes, those simply seeking to play in the water remove the caps and open the valve, providing residents a place to play and cool off in summer.
Since fire hydrants are one of the most accessible parts of a water distribution system, they are often used for attaching pressure gauges or loggers or monitor system water pressure. Automatic flushing devices are often attached to hydrants to maintain chlorination levels in areas of low usage. Many departments use the hydrants for flushing out water line sediments. When doing so, they often use a hydrant diffuser, a device that diffuses the water so that it does not damage property and is less dangerous to bystanders than a solid stream. Some diffusers also dechlorinate the water to avoid ground contamination. Hydrants are also used as an easy above-ground access point by leak detection devices to locate leaks from the sound they make.
Fire hydrants may be used to supply water to riot control vehicles. These vehicles use a high-pressure water cannon to discourage rioting.
In the United Kingdom and Ireland, hydrants are located in the ground. Yellow "H" hydrant signs indicate the location of the hydrants, and are similar to the blue signs in Finland. Mounted on a small post or nearby wall etc., the two numbers indicate the diameter of the water main (top number) and the distance from the sign (lower number). Modern signs show these measurements in millimeters and meters, whereas older signs use inches and feet. Because the orders of magnitude are so different (6 inches versus 150 mm), there is no ambiguity whichever measuring system is used.
In areas of the United States without winter snow cover, blue reflectors embedded in the street are used to allow rapid identification of hydrants at night. In areas with snow cover, tall signs or flags are used so that hydrants can be found even if covered with snow. In rural areas, tall narrow posts painted with visible colors, such as red, are attached to the hydrants to allow them to be found during heavy snowfall periods. The tops of the fire hydrants indicate the amount of pressure each one will put out. It helps make the choice of what hydrants will be used to supply water to the fire scene.
· Blue: 1500 gallons per minute or more; very good flow
· Green: 1000–1499 gallons per minute; good for residential areas
· Orange: 500–999 gallons per minute; marginally adequate
· Red: below 500 gallons per minute; inadequate
The hydrant bodies are also color-coded.
· White: public system hydrant
· Yellow: private system hydrant; connected to public water main
· Red: special operation hydrant; not used except for special procedures
· Violet: Non-potable supply; effluent, pond or lake supply
These markings and colors are required by the National Fire Protection Agency.
In Australia, hydrant signage varies, with several types displayed across the country. Most Australian hydrants are underground, being of a ballcock system (spring hydrant type), and a separate standpipe with a central plunger is used to open the valve. Consequently, hydrant signage is essential, because of their concealed nature.
In Germany, the hydrant marker plates follow the style of other marker plates pointing to underground installations. Fire hydrant marker plates have a red border. Other water hydrants may have a blue border. A gas hydrant would have a yellow background instead of a white one for fire hydrants. All of them have large central T with the installation identification on top of it — an "H" or older "UH" is in the ground and an "OH" is above ground. This photo features a red fire hydrant marker plate, along with another blue special purpose water hydrant marker plate. The numbers indicate the diameter (80 mm) and the location — 2.8 meters in the back, 1.5 meters to the right.
Below are photos of fire hydrants from different countries.
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