Fire hydrants are devices that help the firefighters and other workers to access a source of water for protection against fire or other civil uses like street construction, sewer cleaning, street cleaning, etc. Underground fire hydrants are the most common type of fire hydrant globally. Fire hydrants are an important tool in our world as only a limited amount of water can be stored in fire trucks, which could only be adequate for small fires that happen in an open area or small buildings. Hence, when a large fire happens, the firefighters can extract the water from the nearby fire hydrant to put out the fire. This extracted water could be from public pipelines, lakes, ponds, or any other water sources that are available around the place. It is mandatory to have fire hydrants near all buildings, roadsides, houses, and other industrial areas as it makes it easier for the firefighters to tap in for water supply.
The National Fire Protection Association (NFPA) recommends that each and every fire hydrant should be colour-coded on the basis of its capacity and water source. These colour codes are known by the fire department, hence they can choose the fire hydrants as per their needs. Each colour represents a different capacity and different source from which the water is being extracted. The whole fire hydrant need not be in a particular uniform colour. Some fire hydrants are painted in a neutral colour, and only the knob or head of the hydrant will have the representation colour. As these colour codings are only guidelines and not laws that have been passed, different states and countries choose different colours and different signs to represent their fire hydrants. However, some of the most important and common colour codings are:
Red: The colour red represents that the fire hydrant has a capacity of 500 gallons per minute or less, or we could also say that it is adequate for a two-storied house or building that is about 20 feet tall and 50 feet wide.
Orange: A fire hydrant that is painted orange has a capacity of between 500 and 1000 gallons per minute or less, and that is adequate for a four-storied building or house that is about 40 feet tall and 50 feet wide.
Green: A green coloured fire hydrant or a fire hydrant that has a knob of green colour indicates that the fire hydrant has a capacity of between 1000 and 1500 gallons per minute or less. This could be more than enough for a building or house that is about 40 feet tall and around 60 feet wide.
Blue: A blue-painted fire hydrant is normally said to have a capacity of 1500 gallons per minute or more. These fire hydrants can put out fires in a 4 or 5 story building that is up to 60 feet to 70 feet wide and 40 feet to 50 feet tall.
Some of the colours painted on fire hydrants represent the source of the water supply.
Yellow: The yellow-coloured fire hydrants denote that the water is sourced from a public supply system, like the pipelines to houses and residential buildings.
Violet: A violet fire hydrant indicates that the water is extracted from a lake or pond nearby, or any natural water source.
In and around Australia, there are various types of fire hydrant signage that could signify that the fire hydrants are nearby. Some of those signs are painted markers, which are normally a yellow or white triangle or arrow pointed towards the road where the hydrants could be found. Then there are hydrant marker plates that are actually installed on poles, billboards, street signs, and street fences all around the place, which denote where you could find a fire hydrant.
In Germany, the fire hydrant marker plates have a red border and point to the underground location where the fire hydrant is situated. All the marker plates have a T-shaped symbol on top of them to recognize them easily.
In New Zealand as well, there is a large yellow marker plate on the side of the road with a T-shaped symbol on it, which denotes that the fire hydrant is situated under the yellow marker plate.
In the United Kingdom, fire hydrants are located underground, and there is a large H-shaped symbol that indicates the location of the fire hydrants.
In Finland, the fire hydrant signage consists of blue signboards installed on poles, street fences, and billboards, which state how close the available fire hydrants are by pointing in every direction and naming the distance.
In France, the fire hydrants are situated underground. A red background board with a white symbol on a pole pointing downwards is installed to indicate the place where the fire hydrants are located.
In Canada, the fire hydrant signage is quite simple as it is a yellow board with an image of a fire hydrant in black colour installed on a large pole on every street.
There are two types of fire hydrants, namely wet barrel and dry barrel. Wet barrels give immediate access to water as they are stored right under the surface of the fire hydrant. These types of fire hydrants are installed in places where there is no extreme cold climate, which could freeze the water and make it impossible for the firefighters to extract it. Whereas the dry barrels are installed in places with extreme cold as the water in the dry barrels is stored away under the earth because the earth’s inner core is warmer, and this prevents the water from freezing, hence it could be easily tapped into. Water is extracted from these dry barrels with the help of a valve. In terms of maintenance and repairs, wet barrels are easier to maintain and repair as they are easily accessible, whereas the dry barrel is relatively harder to repair and service.
Some of the main components and parts of a fire hydrant are the bonnet, which helps to prevent water penetration and damage to the fire hydrant. A flange is a device that connects the fire hydrant to the rest of the barrel. A flange actually determines the length of the fire hydrant to make it easier for the firefighters to locate and use the fire hydrant. A stem nut helps in turning and opening the valve, and thrust blocks help in evenly distributing the hydraulic force from the barrel into the soil. A branch pipe helps in the flow of water. The recommended size of a branch pipe is about six inches. Only then can you reduce the loss of pressure and enable a steady and strong flow of water. Some other important parts in a fire hydrant are nozzles, landing valves, panels, and other necessary wiring and couplings. These parts constitute a fire hydrant, both for dry barrels and wet barrels.
There are a number of codes and standards related to fire hydrants introduced by the National Fire Protection Association (NFPA) and many other security authorities. Some of them include NFPA 1, BS 750, DIN 3222, AS 2419, FP 009, IS 3844, NFPA 291, NFPA 25 etc.