All built-upon areas of a community should be served by a water distribution system that not only provides taps for consumer consumption, but also provides approved fire hydrants for installation at locations and with spacing considerations for convenient use by fire department pumping equipment and to meet needed fire flows in the proximity of the buildings to be protected. In North America there are two basic methods for the distribution of fire hydrants in a community. The first method is commonly used in Canada. It is mentioned briefly here because the method has been used in some of the northern States that border Canada. This method is fully described in Water Supply for Public Fire Protection, A Guide to Recommended Practices. (8)
The second method is a linear method document in the ISO’s Fire Suppression Rating Schedule that is used to establish Public Protection Classifications (PPCs) using a scale of 1 to 10, with 1 representing the best possible classification and a 10 indicating no recognized fire protection for establishing insurance rates. While the classification system is somewhat complex, the lower or better the Class number, the lower the property fire insurance rates. In other words, a community classed as an 8 would be expected to pay much higher fire insurance premiums than a community that has a Class 4 rating. The community water supply evaluation accounts for 40 percent of the entire evaluation. The distribution and location of fire hydrants, based on needed fire flows for commercial buildings, is an important part of this evaluation. (4)
The needed location of fire hydrants in a community according to the Grading Schedule criteria can be briefly summarized as follows: The ISO evaluation procedures examines a number of representative locations throughout a community based on the population of the community; the number of installed fire hydrants on the water system; and property types, which include commercial, industrial, and residential properties along with educational facilities, public buildings, such as courthouses, libraries, hospitals, and all other places of public assembly. Buildings upon land areas within a community that do not have a fire hydrant within 1,000 feet of a structure also are evaluated. For a fire hydrant to be credited in the community survey, it must be within 1,000 feet of the property to be protected. Flow tests are conducted to determine that each fire hydrant delivers a minimum of 250 gpm at 20 psi residual pressure for a duration of 2 hours. Installed fire hydrants that do not have this capability receive no credit for insurance rating purposes although they may be used for limited fire suppression capability.
Of importance is that the fire hydrant spacing in a community is also evaluated. For individual property evaluations, the following maximum gpm flow is limited by the hydrant spacing from the risk site. Measurement is made according to the distance that a fire hoseline has to be laid to the fire risk building.
1,000 gpm may be credited for a fire hydrant within 300 feet.
670 gpm for fire hydrants from 301 to 600 feet.
250 gpm for fire hydrants from 601 to 1,000 feet.
Additional spacing criteria may be adopted by local building codes and/or the governmental authority having jurisdiction over a specific building. Commercial buildings that are protected by approved automatic sprinkler systems may have special requirements by individual insurance companies for fire hydrant locations that may be used to reinforce the water supply volume and pressure by fire department pumpers to control and extinguish interior fires. Municipal officials need to call these special needs to the attention of community property protected by automatic sprinkler systems.
In addition to the above provisions, it is a recommended practice that the maximum lineal distance between fire hydrants along streets in congested areas and high fire risk areas with frame buildings and/ or high combustible storage (such as lumber), be located 300 feet apart and a maximum of 600 feet, in light residential areas with building separations of over 50 feet. Other good practices for the installation of fire hydrants calls for at least one fire hydrant at every street intersection, in the middle of long blocks (especially where the needed fire flow exceeds 1,300 gpm), and near the end of long dead-end streams.
Hydrants should be required within large complexes that are accessible to fire department apparatus equipped with mobile pumps.
A key consideration: It is essential that the planning of fire hydrant locations be a cooperative effort between the community water department, the fire department, the building and zoning department, and with the insurance carrier for large commercial and industrial complexes. The proper location of the fire hydrants definitely can have a positive impact on property fire insurance rates.
Installation of Fire Hydrants
The proper installation of fire hydrants on municipal water systems has to give consideration the construction features of the fire hydrant. (10) These include, but are not limited to the following features for providing adequate and reliable water supplies for fire protection.
The nominal diameter of the bottom valve opening needs to be at least 4 inches for supplying two 2-1/2-inch outlets. However, it is recommended that at least one large diameter outlet be provided for the connection hose to a mobile fire department pumper. Today, it is generally recommended that the bottom valve be a minimum of 6 inches.
The net area of the hydrant barrel and foot piece at the smallest part is not to be less then 120 percent of that of the net opening of the main valve.
A sufficient waterway through the fire hydrant needs to be provided to minimize friction loss in the fire hydrant. The hydrant designed should not permit more that 5 psi loss from the main valve intake to the discharge side of the fire hydrant with design flows of no less then 1000 gallons per minute. This information is obtained from the Underwriters Laboratories, Inc. (UL) listing.
A positive-operating, corrosion-resistant drain or drip valve is to be provided.
A uniform sized pentagonal operating nut measuring 1-1/2 inch from point to the flat at the base and 2-7/16 inches at the top. The faces should be tapered uniformly and not less than 1 inch. Fire hydrant bonnets, barrels, and foot piece are generally made of cast iron with internal working parts of bronze. Valve facings should be of a suitable, yielding material such as rubber or a composition material. Fire hydrants are available a number of different configurations, which should be adapted to the installation location.
Types of Fire Hydrants
Two types of fire hydrants are generally in use today. The most common is the base valve or dry barrel, in which the assembly controlling the water supply from municipal water system pipes is below the frost line between the foot valve or “piece” and the barrel of the fire hydrant. This common type of fire hydrant is illustrated in Figure 4-11. The barrel on this type of fire hydrant is normally dry, with water being admitted only when there is a fire or when the hydrant is flow tested; other uses of this fire hydrant are discouraged. A drain valve at the base of the barrel is open when the main valve is closed, thus allowing residual water in the barrel of the hydrant to drain out. This type of fire hydrant needs to be installed whenever there is a chance the temperature will go below freezing, because the valve assembly and water supply are installed below the frost line determined from climatic conditions.
The second type of basic fire hydrant is the wet-barrel type which is normally limited to the southern and western States where protracted freezing is most unlikely; temperatures inside the hydrant barrel must remain above freezing at all times. This type of fire hydrant usually has a compression valve at each outlet, but they may have another valve in the bonnet that controls the water flow to each of the hose outlets. This type of fire hydrant is illustrated in Figure 4-12.
In the side Figure, a base valve, or a dry barrel is illustrated with nomenclature identified. When installed, the valve is below the frost line. This type of fire hydrant also is known as a “frost-proof” fire hydrant. (Source: Mueller Company)
The following guidelines have been prepared by the International Fire Service Training Association. (11)
1) The large-diameter outlet on a fire hydrant, normally 4 inches to 6 inches, should be positioned perpendicular to the curb line on streets or to the edge of the roadway where a fire department can connect hose from the fire hydrant to the intake of the mobile fire pump.
2) The maximum connection distance between the large-diameter outlet on a fire hydrant and the intake connection on a mobile pumper should not exceed 15 feet; less than 10 feet is preferable except for special situations such as parking lots and parking garages. The responsible fire department should be consulted on special fire hydrant installation problems.
3) There should be no obstructions within 10 feet of any installed fire hydrant. Such obstructions generally include traffic standards, sign posts, utility poles, trees, shrubbery, and fences. A wet-barrel or California-type fire hydrant maybe used where freezing temperatures are not encountered. There is a compression valve at each outlet. (Sources: Mueller Company)
4) The clearance between the bottom of any hydrant capped outlet to the ground level or hard surface levels is not to be less than 18 inches. To provide for connecting different types of hose fittings to the fire hydrant.
5) All fire hydrants needs to be painted a bright color and that color maintained for visibility by approaching fire apparatus from all directions.
Drainage is necessary for fire hydrant equipped with drain ports, and can be provided by excavating a pit about 2 feet in diameter and 2 feet below the base of the fire hydrant and filling it compactly with course gravel or stones placed around the bowl of the fire hydrant to a level 6 inches above the waste opening. If the drip valve of the hydrant is below ground water level, it maybe plugged to exclude ground water. In this case, water should be pumped out to prevent freezing. This same procedure should be followed for older installed fire hydrants not equipped with drain features and that have been install for many years. (10)
General Maintenance of Fire Hydrants
A major item of periodic maintenance recommended on a quarterly schedule is a check for any external damage to each fire hydrant and a check for leaks in the fire hydrant mechanism that include
1) the main valve assembly when the fire hydrant is closed,
2) the drip valve when the main valve is open but outlet are capped, and
3) the mains the supply each fire hydrant. Stethoscope-like listening devices are available to make these checks.
Maintenance routines provide for an operating test, repair of any leaks, and pumping out of fire hydrants where necessary. Threads of the outlet, caps, and the valve steam should be lubricated with graphite. Hydrants should be kept painted on a scheduled basis for proper location during an emergency, but care should be taken to avoid accumulation of paint that might prevent easy removal of caps or operation of valve stems. (10)
Optimal positioning, spacing, location, and marking of fire hydrants can aid the fire service during emergency operations. Public fire hydrants are often under the purview of a local water authority, many of whom use American Water Works Association (AWWA) standards for fire flow and other criteria. The building design team is often responsible for hydrants and water supply systems on privately owned property sites. Both the IFC and NFPA 1 include appendices that give criteria for fire flow, and fire hydrant location and distribution. Other criteria can be found in NFPA 24, Standard for the Installation of Private Fire Service Mains and their Appurtenances.
Typically, hydrants have a large suction hose connection (41/2 inches is a common size) called a “pumper outlet” or a “steamer” connection. Plus, they normally have two, 21/2 inch hose connections. Both wet-barrel type hydrants and the dry-barrel types used in areas subject to freezing have these features. Dry hydrants (those connected to a static source such as a tank, well, or pond) often have only a large connection or pumper outlet. Criteria for dry hydrants can be found in NFPA 1142, Standard for Water Supplies for Suburban and Rural Firefighting.
Hose can be connected directly to a fire hydrant only if the connections match those needed by the area fire service. This includes type (threaded or quick-connect), thread style and size of connection. If the connections do not match, adapters (if available) will slow response.
Optimal location and positioning of hydrants facilitates rapid connection of hose lines and devices. Considerations for designers include height, orientation, distance from the curb, and distance from surrounding obstructions (Figure 2.14). A clear distance is essential around the hydrant to enable a hydrant wrench to be swung 360 degrees (see Figure 2.16b) on any operating nut or cap nut. If the nearby obstruction is a plant or bush, consider its potential growth when planning for hydrant placement.
Maximum distance between hydrants differs greatly, depending on various local standards. IFC and NFPA 1 both include tables within appendices that enable a designer to find the required fire flow for any given building, and then select the corresponding hydrant spacing. Where apparatus may approach from different directions, hydrants should be placed primarily at intersections. If additional hydrants are needed to comply with local spacing requirements, they should be spaced along blocks at regular intervals.
Pumpers may utilize hydrants in different ways. If the fire is close enough, a pumper can be positioned at a hydrant and use a large-diameter suction hose (Figure 2.15). Pumpers in urban and suburban areas with hydrants are generally equipped with large-diameter suction hoses connected to an intake on the pumper’s front bumper, rear step, or side. This suction hose may be as short as 15 feet. In many urban areas, however, pumpers carry longer suction hoses in order to reach hydrants on the opposite side of a single line of parallel parked cars.
If a fire is not close to a particular hydrant, a pumper may have to lay one or more hose lines between the hydrant and the fire. If a pumper lays a supply hose line from a hydrant towards the building with the fire emergency, this is called a “straight” or “forward” hose lay (Figures 2.16a and 2.16b). The opposite (laying supply hose from a building on fire to a hydrant farther down the street) is called a “reverse lay” (Figure 2.16c). Many fire departments use one or the other of these options as their standard procedure. Designers should take this into account when locating hydrants. For instance, hydrants at the end of dead-end streets will not facilitate straight hose lays.
Hydrants that are too close to a particular building are less likely to be used due to potential fire exposure or collapse. Locating hydrants at least 40 feet away from protected buildings is recommended. If this is not possible, consider locations with blank walls, no windows or doors, and where structural collapse is unlikely (such as building corners). A rule of thumb for collapse zone size is twice the distance of the building’s height. This is not a consideration in urban areas, where a multitude of hydrants are available for any given location.
A number of methods are used to enable firefighters to rapidly identify hydrant locations. The color used for hydrants should contrast as much as possible with the predominating surroundings. Some localities place reflective tape around the hydrant body. Other jurisdictions mount reflectors (usually blue) in the roadway in front of each hydrant; however, in cold weather climates these reflectors are often obstructed by snow.
The best way to identify hydrants in areas subject to snowy weather is a locator pole which is visible above the highest expected snowfall. These are reflective or contrasting in color, and some have a flag, sign, or reflector mounted on top (Figure 2.17). These poles should be flexible enough to return to their upright position if someone tampers with them, or rigid enough to prevent this type of tampering. Some jurisdictions or sites go so far as mounting a light (usually red or blue) above the hydrants.
A color coding system may indicate flow capability of hydrants. One such system is contained in NFPA 291, Recommended Practice for Fire Flow Testing and Marking of Hydrants.
During construction or demolition, fire hydrants may be out of service. Designers should specify that inoperative hydrants be covered or marked during their projects, so that firefighters will not waste time attempting to use them.