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Fire Hydrants

Fire Hydrants are an integral part of private fireline construction and public water pipeline main systems. Fire hydrants are basically outlets that release large quantities of pressurized water to extinguish fires. Public fire hydrants are typically supplied by municipal potable water pipeline mains; whereas private fire hydrants are typically located behind a detector check and specifically only used for fire suppression and is not typically drinking water.

Public fire hydrants are usually designed and spaced to be installed in a new construction setting approximately every 500 ft. They are usually located along a street, in the sidewalk at a certain distance away from the curb. Each public fire hydrant typically includes a gate valve on the branch off the municipal water pipeline supply.

Fire hydrant outlet sizes and number of outlets are determined by local zoning requirements and local fire department codes. Fire hydrants are designed with an operating valve for each outlet. Outlets can range in size from 2 ½ to 4 ½ inches in diameter. Outlets range from two to three outlets, in most cases.

As mentioned, private fire hydrants are located behind a check valve. These fire hydrants are used specifically for fire suppression and are typically connected to a system that feeds a building's fire sprinkler system. Their location and quantity vary depending on what type of structure or property they are servicing.

There are generally two types of fire hydrants used in most instances. Whether serving public or private systems, they are either wet barrel or dry barrel fire hydrants. Wet barrel fire hydrants are pressurized up to their outlets and each outlet can be operated individually. Dry barrel fire hydrants are not pressurized up to their outlets. Instead, there is only one internal valve, generally located at the base of the fire hydrant bury, that when opened, will pressurize all outlets at the same time.

Another difference between the two fire hydrant types is that the dry barrel, if struck or hit and separated from the base, will allow the valve in most cases to close, thereby not allowing water to be discharged. In contrast, wet barrel fire hydrants, if struck, do not have this feature. To combat this, several municipalities have introduced the use of a break-off check valves located just below the head of wet barrel fire hydrants.

The most common fire hydrant design installed by pipeline contractors in Southern California for both private and public fire line construction is the wet barrel fire hydrant. On an interesting note, several municipalities that once required dry barrel hydrants are able to retrofit the current existing dry barrel hydrant model and convert it to a wet barrel hydrant. Fireline systems, whether for public or private use, and their respective fire hydrants, will always be a fundamental component to any pipeline infrastructure.