Waterworks and sewer systems are the mark of a developed society. Not only do we require clean, running water to maintain residential neighbourhoods and businesses, we need to access it quickly and easily to fight fires.
Fire hydrants work by tapping into a pressurized system. Firefighters fasten a hose to nozzles on the hydrant and pump water with varying water flow volumes. The colour of the hydrant’s body and nozzles indicates if the available water flow is high, moderate, or low.
There are two classes of street-side fire hydrants – wet barrel and dry barrel – which have dramatically different structures and permit different firefighting procedures. In addition, a fixture called a standpipe facilitates firefighting within buildings and works like an overhead sprinkler system. Each hydrant style brings great benefits, but due to certain structural differences, they don’t work uniformly for every municipality. Let’s examine each type of fire hydrant so you can determine which is right for your district.
Wet Barrel Hydrants
A wet barrel hydrant’s basic, sturdy design gives it an operational lifespan of more than 100 years. Its mechanical parts are above ground, with a main valve to prevent any debris from entering the hydrant. Easy-to-access outlet valves and nozzles work independently so that firefighters can add more discharge lines without causing the hydrant to shut down.
All of these convenient above-ground aspects of wet barrel hydrants also make them susceptible to frost. Therefore, wet barrel hydrants aren’t prevalent here in Canada, but they are commonly found in the hot, southern regions of the United States.
Dry Barrel Hydrants
The main valve in a dry barrel hydrant sits at the hydrant’s base. The water line is entirely subterranean, below the frost line, and adjacent to the main valve. When the valve opens, the barrel pressurizes and fills; firefighters can then pump water through the hooked-up hose. When they close the hydrant’s valve after they put a fire out, the barrel drains. Because no water stays within the hydrant, there’s no risk of freezing.
Types of Dry Barrel Hydrants
There are three types of dry barrel hydrants: slide-gate, toggle, and compression.
- In a compression hydrant, a vertical stem works like a piston. It moves toward or away from a seat to close and open the main valve.
- In a toggle type of dry barrel, a vertical stem with two toggle arms rotates to open the main valve at the hydrant’s base.
- In a slide-gate hydrant, a threaded stem lifts or pushes down a gate that controls the main valve.
Hydrant manufacturers design and produce variations on these models and customize them to meet the needs of each municipality or private property.
Nozzle cap colours indicate how much flow is available.
Blue-painted nozzles indicate the hydrant has the highest flow available, at 95 litres per second.
Green caps indicate a water flow of 63 to 95 litres per second.
Orange paint shows pressure at 31 to 63 litres per second.
Red nozzles signal the lowest possible flow at 31 litres per second or less.
Densely populated areas tend to have high-flow, high-pressure hydrants. Suburban or rural residential areas often don’t have high-pressure systems because of their small pipes.
What about a fire hydrant’s body colour? Body colours must be bright and recognizable. Municipal and provincial systems usually have yellow hydrants; however, some older systems are bright red. Various other body colours were used in the past, including silver, white, and lime. The international colour for non-potable water is violet, meaning the water source comes untreated from a lake or pond. Non-working hydrants should be tagged “Out of Service.”
Standpipes: The Interior Solution to Firefighting
Have you ever noticed a fixed interior pipe running vertically in the corner of a staircase? This is a standpipe. It allows one person to extinguish part of a building fire after its occupants evacuate.
Standpipes are a dependable alternative to automatic, overhead sprinkler systems. The person operating a standpipe can turn off the hoses right away, preventing the large-scale, interior water damage common with sprinkler systems. Standpipes also provide a method of fire suppression to people unable to exit the building.
Which One Should You Choose?
A high-quality fire hydrant manufacturer will not only know the specifications necessary to meet your municipality’s standards, but will also customize your hydrants to match the style, water flow, and colour you need. Contact Terminal City Iron Works to help you make a well-informed decision about which hydrant is right for you.