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Here’s why fire hydrants come in different colours


Photo by Dan licensed CC BY 2.0

You see them a million times a day walking down the street: fire hydrants! You probably know that they’re there to help put out fires, but how do they do that? And why aren’t they constantly spewing water? To learn the answers, keep reading!

What is a fire hydrant?

Yellow fire hydrant.
Photo by Ben Babcock licensed CC BY 2.0

A fire hydrant is simply a point where people are able to tap into a water supply. The most common use for them is to assist firefighters in putting out fires. By connecting a hose to a hydrant, they gain access to all the water they need to douse a burning building!

But how do they work?

Fire hydrants are connected to a large water supply through underground pipes. When firefighters arrive on the scene, they connect a hose to the side of the hydrant. Once the hose is connected, a special wrench with a pentagon-shaped socket is used to turn the nut on the top of the hydrant. This unique tool is not widely available, so only authorized people, like firefighters, can use hydrants.


Fire hydrants on a truck.
Photo by Mike Mozart licensed CC BY 2.0

Once the nut is turned, it opens a valve deep underground that allows water to start to flow into the hydrant. Most fire hydrants have these valves underground for a few reasons. If water were kept in the hydrant at all times, it could easily freeze in cold weather, possibly damaging the hydrant and making it impossible to access water when needed. Also, if water was stored in the hydrant, it could start flowing uncontrollably if it were, for example, hit by a car.


Fire hydrant connected to fire truck.
Photo by Real Grouchy licensed Public Domain

The hose connected to they hydrant is usually also connected to a fire truck. The water coming from the hydrant is then run through a pump, which helps to increase the water pressure, and can also divide the supply to multiple hoses.

Why are some fire hydrants different colours? 

Red and blue fire hydrant.
Photo by Dan licensed CC BY 2.0

The two most common colours for fire hydrants are bright shades of red and yellow. These colours are used because they stand out, which makes hydrants easier to find in emergencies. In some places, the tops of fire hydrants are painted different colours to let firefighters know how many gallons per minute, or GPM, a hydrant is able to deliver. The higher the GPM, the better the hydrant will be at fighting bigger fires. Blue usually marks the highest GPM, and red the lowest!

What did people use to fight fires before fire hydrants?

Fire buckets.
Photo by Timitrius licensed  CC BY-SA 2.0

Before the invention of fire hydrants and fire trucks, most places used something called the bucket method: people would form a line between a water supply (a river, for example) and the fire. The first person would fill a bucket with water and pass it on. The last person would then toss the bucket of water onto the fire. This would continue until the flames were quenched.