Understanding How Fire Hydrants Work: Debunking Movie Myths and More

Have you ever seen a movie where someone drives a car into a fire hydrant and water sprays up into the air, leading to scenes that seem so unrealistic that they raise more questions than answers? In reality, the science behind fire hydrants is both fascinating and crucial to understand. In this article, I will delve into the inner workings of fire hydrants and address some common misconceptions.

The Myths of Fire Hydrants in Movies

In films, the scenario of driving a car into a fire hydrant and causing water to gush out is a staple trope. However, in real life, this doesn't quite happen as depicted. Movies often have the characters or stunt drivers open the valves before impact to create a geyser of water. This is not the case in reality. Let me break down the real mechanism behind these hydrants.

Types of Fire Hydrants

There are two main types of fire hydrants found on city streets: dry barrel and wet barrel. Each has its unique characteristics and design to meet the needs of different climates and conditions.

Dry Barrel Hydrants: Ideal for Cold Climates

These hydrants are found in areas where freezing temperatures are a concern. A dry barrel hydrant has a valve located below the freeze line, which is closed unless the hydrant is in use. This valve is crucial in preventing water from freezing inside the hydrant, which could cause extensive damage. Each dry barrel hydrant has an operating nut on top that you can use to shut off the hydrant when it's not in use. To prevent damage from accidental impact, the operating rod has a ldquo;breakawayrdquo; feature. This ensures that if the hydrant is hit, the operating rod will separate without damaging the valve. Consequently, there will be no water column shooting up.

Wet Barrel Hydrants: Suitable for Temperate Climates

Wet barrel hydrants are used in areas that do not experience freezing temperatures. They are easily recognizable due to the presence of a valve operating nut on each hose outlet, located directly opposite the hose outlet. These hydrants are always full of water, as the valves are located within the hydrant body. If a wet barrel hydrant is broken, water will immediately spurt out, creating that iconic scene. No valve opening is necessary beforehand to get the water column shooting up.

Shutting Down Fire Hydrants

In addition to the valve on top of the hydrant, there is another safety mechanism in place. Each fire hydrant is connected to a ldquo;street valverdquo; that is buried near the hydrant. This street valve serves as the ldquo;shut off switchrdquo; for the entire water supply leading to the hydrant. This valve is operated using a special wrench called a ldquo;valve keyrdquo; when the hydrant needs to be shut down for maintenance or replacement. To access the street valve, one must remove a small manhole-style cover.

Key Takeaways

Types of Hydrants: Dry barrel and wet barrel hydrants serve different climatic needs. Valves in Hydrants: Dry barrel hydrants have valves below the freeze line, while wet barrel hydrants have valves inside the hydrant. Breaking the hydrant in a wet barrel scenario will cause a water geyser to shoot up. Street Valve: The ldquo;shut off switchrdquo; is accessed through a specially designed valve key and requires a manhole-style cover to be removed.

Understanding how fire hydrants work is essential for both emergency services and the general public. Knowing the differences between dry and wet barrel hydrants, as well as the importance of the street valve, can help prevent misunderstandings and ensure effective use during emergencies.