Water distribution systems provide not only potable water for drinking and other uses, but they also supply water for fire-fighting through fire hydrants. Most distribution systems contain numerous hydrants, which are located throughout the community, many in areas that are not easily guarded or protected. In addition, because hydrants are designed to be used in an emergency, they must be accessible and easy to operate, and, thus, they cannot be secured in an enclosure or otherwise protected as can many water system components (e.g., valves, pumps.) The purpose of this document is to provide an overview on how fire hydrants work, and to describe the options available for providing additional security to the hydrants.

Fire hydrants are directly connected to water distribution mains to allow quick access to potable water throughout a municipality for the purpose of extinguishing a fire. There are two types of hydrants: "dry" barrel and "wet" barrel. A cross-section of a standard dry barrel fire hydrant is provided in Figure 1. In a dry barrel hydrant, the vertical portion of the hydrant, or the "barrel," is empty of water. The hydrant is equipped with a stop valve at the barrel's bottom (see Figure 1) that prevents water from entering the barrel during normal conditions. To operate a dry barrel hydrant, the hydrant cap (see right side of Figure 1) is removed, and the nut on the top of the hydrant is turned, lifting the stop valve and allowing water to flood the hydrant barrel. The hydrant is equipped with drain holes that allow water to exit the barrel when the valve is closed after operation. Dry barrel hydrants are typically used in cold weather climates to prevent water from freezing in the barrel, which could damage the hydrant and hinder its operation in an emergency.

Wet barrel hydrants operate similarly to dry barrel hydrants; however, the barrel is constantly filled with water. Wet barrel hydrants can be used in locations where there is limited potential for freezing.

Hydrants are typically designed and operated to minimize risks of backflow from the hydrant into the distribution system. Typically, a hydrant is allowed to flow for a short time to clear any internal debris in the hydrant before a hose is attached for use in an emergency situation. Hydrants can also be upgraded with mechanisms to prevent backflow to the potable water distribution system. Other security products have been designed to protect fire hydrants from other forms of unauthorized tampering. These products and options are discussed below.

Figure 2 is a summary of options available for providing additional security at an individual fire hydrant. As can be seen in the figure, there are two different types of protection that are available for hydrants: intermittent access protection and continuous protection. The security options for each type of hydrant use are detailed below.

Intermittent access protection may be most appropriate in a situation where a hydrant will be used on an "as necessary" basis by an outside source, such as a construction contractor. In certain municipalities, a permit is required, or a metering device must be installed on a hydrant for this type of operation. If possible, inclusion of a few simple security measures in this process would be the most favorable means of implementing intermittent access protection. First, one or a few hydrants throughout a municipality can be selected for outside access, which will limit the amount of monitoring required. Security experts recommend that these hydrants be near or at the end of a distribution line or in an area with minimal consumers. That way, in the event that a contaminant is introduced, distribution to the community will be kept to a minimum.

Secondly, a municipality can install or require installation of a backflow prevention device (either a check valve or an air gap drain [i.e., hose]) on the exterior or outlet of the selected hydrant(s) to ensure that no water will flow from the outside source into the potable water distribution system. The only drawback associated with these devices is that there is a pressure drop across all backflow prevention devices, which increases dramatically as flow increases. In areas where there is limited flow and pressure, this could decrease the fire flows from the hydrant necessary during an emergency situation. Additional information on each of these options is available in the Backflow Prevention Devices Product Guide.

Several security products have been designed to protect an individual fire hydrant against tampering and vandalism at all times - 24 hours a day, 7 days a week. Certain devices can be easily installed on the exterior of the hydrant, while others can be permanently constructed as part of the distribution system or installed internally to the hydrant. As indicated in Figure 2, there are two primary options for a municipality looking to provide continuous protection for their fire hydrants: installation of backflow prevention devices and/or hydrant locks.

As designated by the square shape in Figure 2, hydrant locks are installed external to the potable water distribution system. Typically the locking device is placed over the operating nut on top of an individual hydrant to prevent an unauthorized individual from operating the hydrant. Certain products also include a mechanism that will lock the hydrant cap and prevent it from being removed. Fire hydrant locks can be easily installed by municipal fire departments or water maintenance crews, and are relatively inexpensive. The only drawback associated with these devices is that, prior to operating the hydrant and depending on the type of lock, either a special key or wrench is required, or the lock must be removed. The time spent removing the lock may also impact response time, although the time impacts should be minimal. Loss of the key or specialty wrench, or failure to bring the correct key or wrench, could severely impact the response time in an emergency situation. Refer to the Fire Hydrant Locks Product Guide for more detailed information on these security products.

Although backflow prevention devices can be installed externally for intermittent protection, devices installed internally to the potable water distribution system can provide a more continuous level of security because intruders cannot remove them. There are two types of internal backflow prevention devices that can be installed for continuous protection: a check valve located in a below-ground vault; and an internal hydrant valve. Each of these products is discussed in more detail below.

• Check Valve in Vault - A check valve can be directly installed either in a water main distribution line, or in the pipe that is directly connected to the fire hydrant, to prevent the flow of any contaminant or debris back into the potable water distribution system. Typically the check valve will be placed within a below-grade vault so that the valve can be easily accessed for maintenance purposes. This is a highly effective method of protecting the water distribution system; however, it can be quite costly, and placing a below-grade vault at every fire hydrant would be difficult. This type of backflow prevention device may be most practical if it is installed during construction of a new water line in critical locations throughout a municipality. For example, this would be highly effective where a water main enters a subdivision to prevent the introduction of a contaminant that could potentially be distributed to an entire neighborhood. However, this is not a typical installation. Additional information on check valves can be found in the Backflow Prevention Devices Product Guide.



• Internal Hydrant Valve - One manufacturer has developed a backflow prevention device that can be installed internally to an individual hydrant. A cross-section of this device in a fire hydrant is provided in Figure 3.

  Figure 3. Davidson Anti-Terrorism Valve, Windsor Technologies, Inc.

  The operation of the device is relatively simple. In the closed position, a stainless steel spring holds the valve in place on the seat, which is positioned just below the outlet inside of the hydrant. The location of the valve and seat in the closed position prevents anything from falling into the hydrant barrel. When the hydrant operating nut is turned, the flow of water from the main lifts the valve and water discharges from the hydrant outlet. When the operating nut is closed, the valve returns to the closed position. This device is also equipped with two seals that ensure that the device is water-tight between the valve and the shaft and at the valve-seat connection point.

  When installed properly inside a fire hydrant, the device is not visible when the hydrant cap is open , and, thus, potential intruders will not know that the hydrant is protected. In addition, the device should not impact access to the fire hydrant, and it may even improve response time because the hydrant does not need to be flushed out before use to remove potential debris in the barrel.

  The only drawback associated with these devices is that there is a pressure drop across all backflow prevention devices, which increases dramatically as flow increases. In areas where there is limited flow and pressure, this could decrease the hydrant's fire flow below requirements during an emergency situation.

Costs for backflow prevention devices and fire hydrant locks can be found in the Backflow Prevention Devices and Fire Hydrant Locks Product Guides, respectively.

The internal fire hydrant valve costs $350 to $450 per hydrant, based on the hydrant size, configuration, and fire flow delivery requirements. This cost includes the complete device (valve, seat, shaft, stem and rings) and training on how to install the device. Installation of the device in an individual hydrant can be accomplished by a municipal crew in approximately 30 to 40 minutes, and requires removal of the above-grade portion of the hydrant. Installation services are also available from Windsor Technologies for an additional $125 each.