Do firefighters spray water from a fire hydrant directly onto a fire?
And by the way, why are fire hydrants even necessary? Don’t fire trucks have huge tanks of water?
Fire hydrants are everywhere. Sometimes called fire plugs, these short, stubby iron devices can vary in size, color and appearance, but they’re usually shaped like a cylinder with a variety of valves and connection points.
You probably already know that fire hydrants allow firefighters to access a local water supply quickly.
But what about all the water that fire trucks bring to a fire?
Fire trucks do have tanks of water. But in many cases, in spite of their large size, they don’t hold enough water to fight a fire effectively. So, most of the time, the water to fight a fire comes from a fire hydrant which supplies a seemingly unlimited volume of water from the local underground water lines. A fire truck will usually haul enough water to allow firefighters to begin to fight a fire while hoses are being connected to the nearest fire hydrant.
Furthermore, firefighters usually do not run water from a hydrant, through a hose and then directly onto a fire. It’s typically pumped through hoses from a fire hydrant to a fire truck, where it is pressurized and divided into several streams to supply water to multiple fire hoses at once. Basically, each fire hydrant can be leveraged for considerably more fire-dousing power when it’s run through a truck.
By the way, firefighters usually have to use a special wrench to remove the valve covers on a fire hydrant. (The idea is to make it challenging for non-firefighters to open a fire hydrant). Once the covers are removed, firefighters can attach hoses to the valves that allow water to flow through the hydrant into the hoses.
Fire hydrants are often painted a bright color, such as red or yellow, which helps firefighters find them easily when needed. In some areas, local laws require that fire hydrants be painted particular colors depending upon how much water they’re able to supply at a particular pressure. This helps firefighters to determine which fire hydrant is the best to use for a particular situation.
WET-BARREL VS DRY-BARREL HYDRANTS
Wet and dry fire hydrants are two categories of design. The terms “wet” and “dry” indicate whether or not water exists in the top of the hydrant when it’s not in use.
Wet-barrel hydrants represent the original design and can still be used in warm climates where there is no risk of freezing. With wet-barrel hydrants, the shut-off valves are above ground, so there’s water in the barrel even when the hydrant is not in use. Each outlet has a valve that operates independently, and the mechanical parts are easy to access. This makes wet-barrel hydrants easy to operate and easy to maintain in warm climates where there is no danger of freezing.
Dry-barrel hydrants solve the problem of freezing inherent in cold climates. The solution is simply to keep the water underground, below the ground freezing level, so that even in the winter, the water is liquid and does not turn to ice. With this dry-barrel design, the barrel of the hydrant is drained or pumped dry when the hydrant is not in use and the shut-off valve is located underground. The valve is still operated above ground, but the valve itself is well below the hydrant. In other words, there’s no water left above ground after the hydrant has been used, so the hydrant is safe from freezing in cold regions. The water is simply accessed when needed.
Way back before modern water pipes distributed water underground, water for firefighting had to be kept in buckets ready for use by ‘bucket-brigades’ or brought to the fire with a horse-drawn fire-pump.
Starting in the 16th century, wooden pipes were used to distribute water. Firefighters would dig down to the pipes and drill a hole to access water for the buckets or pumps. This had to be filled and plugged afterward, hence the common U.S. term for a hydrant as a ‘fireplug’. A marker would be left to indicate where a ‘plug’ had already been drilled to enable firefighters in the future to find previously-drilled holes.
Later on, these same wooden water pipe systems utilized pre-drilled holes and plugs.
When cast-iron pipes replaced wood pipes, permanent underground access points were made available for firefighters. Some countries provide access covers to these points, while others attach above-ground hydrants.
The first cast-iron ones were patented in 1801 by Frederick Graff, then chief engineer of the Philadelphia Water Works. Improvements since then have evolved to address problems such as tampering, freezing, connection, reliability, etc.