How Do Fire Hydrants Work?

If you have ever seen a fire truck or fire engine in action, then you will have seen the hoses spurting with water.

But where does the water come from? Does the fire truck carry large quantities of water?

Fire trucks do carry some water, but it is not enough to extinguish a big blaze. This is where fire hydrants come in.

They provide the hoses with more water to make it easier for the firefighters to extinguish the fire. 

But how do fire hydrants work? Where does the water come from? If you want to know more about fire hydrants then keep reading.

We have put together this helpful guide to tell you everything you need to know. 

How Do Fire Hydrants Work

What Do Fire Hydrants Look Like?

Fire hydrants can vary in appearance, but they tend to be cylindrical in shape with several outputs and valves. 

They are made of iron, so they are very solid, and they can be found on street corners close to the curbside.

Fire hydrants are always painted with bright colors like red and yellow. This is so that the firefighters can spot them easily and quickly in the event of an emergency.

The different colors signify how much water can be provided by that particular fire hydrant, and the pressure of the water.

This is so that the firefighters can plan how to tackle the fire and what equipment they will need to use. 

You can also get underground fire hydrants. The chamber is covered with a metal lid that is marked with a symbol or the letters ‘FH’. 

Where Does The Water Come From? 

Fire hydrants are supplied by the local water supply - the same water that supplies your home and runs out of your faucets.

The fire hydrants are positioned to give fire firefighters convenient access to the water supply to give them a better chance of putting out the fire and preventing property damage, death or serious injury to the people involved. 

Even though the fire hydrant makes it easier for firefighters to access water, it can still take several minutes to set up.

This is why the fire trucks carry a supply of water - this water can be used to start to tackle the blaze while they are waiting for the fire hydrant to be set up. 

How To Turn On A Fire Hydrant?

How Do Fire Hydrants Work?

If you try to get water out of a fire hydrant, you won’t be able to. This is because you need a special shaped wrench that is only given to firefighters.

It is important that fire hydrants are used for their designated purpose in order to prevent floods and water damage or a waste of water. 

Firefighters will use a special pentagonal wrench to take off the valve covers. They can then attach the hoses to the outlets.

Once the hoses are attached, they can twist the wheel or lever that controls the valve, open it, and allow the water to flow through.

If it is an underground fire hydrant then the firefighters will need to lift the lid, attach a standpipe, attach a hose to the standpipe, and then use a key to turn the valve to turn the water on. 

The hoses carry the water to the fire truck. From here, it is pressurized and split across the various fire fighting equipment.

This allows multiple firefighters to tackle the blaze, and for several areas of the fire to be dampened at once. This is much more efficient than just using one stream of water. 

Who Owns Fire Hydrants?

Fire hydrants on public land are owned by the local water company who have a duty to allow the fire department to use the water in the event of an emergency.

The fire department will carry out regular inspections and maintenance to ensure that the fire hydrants in the area remain in working order.

If there are any major issues that require a repair job rather than standard servicing and maintenance then the fire department will notify the water company who will take over. 

Fire hydrants on private land are owned by whoever owns the land. The owner is also responsible for the maintenance and upkeep of the fire hydrant.

It is important to keep any fire hydrants on your land in good condition, as they can make a big difference in the event of a fire. 

What Are The Main Components Of A Fire Hydrant? 

Fire hydrants can be broken down into several main components: 

  • Bonnet - The bonnet of the fire hydrant is the rounded metal covering on the top that protects the hydrant from damage. 
  • Branch - The branch pipe connects to the main water supply so that the water can travel through the fire hydrant. The diameter of the branch pipe changes the water pressure. 
  • Operating system - The operating system is the pipe that connects the branch pipe and valve to the outlet. 
  • Valve - The valve is at the bottom of the operating stem and connects to the branch pipe. It can be opened or closed to control the flow of water 

When Were Fire Hydrants Invented?

Fire hydrants were invented in the early 1800s by Frederick Graff Senior. He worked for the Philadelphia Waterworks as a chief engineer.

The initial design was referred to as a ‘wet barrel’ design, as the part of the fire hydrant that is above ground contained water.

This was not suitable for all areas and climates, as once the temperature drops below zero the water will freeze.

This could cause the fire hydrant to burst, or it could prevent firefighters from being able to use the hydrant. 

The design was updated to a ‘dry barrel’ design, where all of the water remains underground until the fire hydrant is activated by a firefighter.

This prevents the water from freezing and makes the fire hydrants much more efficient. 


Fire hydrants are a simple but effective design that are vital to firefighting.