During the past decade, an ongoing debate over life safety benefits versus water regulations has developed between the fire protection community and the local water authorities.

Issue: 7/04

During the past decade, an ongoing debate has developed between the fire protection community and the local water authorities. While the debate continues, many areas of agreement and compromise have developed. The fire protection community has begun to understand the very strict local, state and federal regulations that all water authorities must comply with. The water authorities have long understood the life safety and property protection benefits of automatic fire sprinklers. Now, they have begun to understand the real cross-connection risks associated with each type of fire sprinkler systems and the impact automatic fire sprinkler systems can have in reducing the demand and infrastructure associated with providing fire protection water. In fairness, the fire protection community has also had to understand and accept the same real risks associated with each type of fire sprinkler system, in order to fully understand the water authority's concerns. Here is a brief summary of both of these concerns.

Water Authority Responsibilities

The water authority has the responsibility to provide safe and reliable drinking water to all customers. Because of this responsibility, all types of cross-connections must be addressed, including automatic fire sprinkler systems.

Fire Protection Needs

All automatic fire sprinkler systems need an adequate and reliable supply of water. With its long track record and strict performance requirements, the municipal water distribution system is the most reliable and largest source of water supply for automatic sprinkler systems. In order to provide economical fire sprinkler systems, all advantages of the available water supply need to be utilized. Where this becomes a key issue for the fire protection community is in available system pressure. As the available pressure is reduced due to system friction loss or added friction loss from backflow prevention assemblies, the need for fire pumps becomes more prevalent and significantly increases the total cost of the system.

Fire Sprinkler Systems-Community Impact

Automatic fire sprinkler systems not only have an impact on community life safety and property protection, but they also have a significant impact on a community's water supply by reducing the amount of water used to control fires. For residential fire sprinklers systems, the required water demand to control a fire is reduced by approximately 88% (Scottsdale 15-Year Study). Because of this reduction in water usage, it allows a community to reduce the size of the water mains and the number of hydrants can also be reduced. Scottsdale, AZ, a sprinklered community for over 15 years, has had an infrastructure savings of $7 million dollars as a result of uniform application of automatic fire sprinkler systems. Additionally, the community benefits from the added life safety and property protection. In Scottsdale during the 15-year study, there were 49 fires in sprinklered homes with no fatalities, and during the same time, 13 people died in fires in non-sprinklered homes. During the 15 years, the average loss per fire without sprinklers was $45,019, whereas the average loss per fire with sprinklers was $2,166. Automatic fire sprinkler systems effectively reduced the average loss per fire by 95%. Research like the Scottsdale report has gone a long way toward documenting the total community impact that automatic fire sprinkler systems can have on the community from a fire protection, as well as a water authority, perspective.

American Water Works Association Research Foundation

The American Water Works Association (AWWA) Research Foundation has published a study on the impact of fire flow on water distribution systems titled, "Impact of Fire Flow on Distribution System Water Quality, Design, and Operation." The conclusion states that:

"Water-efficient fire suppression technologies exist that use less water than conventional standards. In particular, the universal application of automatic sprinkler systems provides the most proven method for reducing loss of life and property due to fire, while at the same time providing faster response to the fire and requiring significantly less water than conventional fire-fighting techniques. It is recommended that the universal application of automatic fire sprinklers be adopted by local jurisdictions."

As mentioned earlier, both the fire protection community and the water authorities are beginning to understand the impact and the benefits that each group brings to the table. The question now is where are we today? The following summaries should provide a much clearer picture of the requirements and recommendations, and hopefully, some detailed guidance for designing and specifying automatic fire sprinkler systems.

AWWA M-14 Recommendations

AWWA M-14 is the American Water Works Association's manual for the "Recommended Practice for Backflow Prevention and Cross-Connection Control." The current 2004 edition of M-14 is the third edition. The previous edition (1990) had six classes of cross-connections for fire sprinkler systems. The current edition has replaced them with a classification system that depends on the degree of hazard presented by the fire sprinkler system. The degree of hazard in general is either considered low hazard or high hazard. A low hazard cross-connection is a non-health hazard. It is a potential cross-connection that involves any substance that generally would not be a health hazard but would constitute a nuisance or be aesthetically objectionable if introduced in the potable water supply. A high hazard cross-connection is a health hazard. It is a potential cross-connection involving any substance that could, if introduced into the potable water supply, cause death or illness, spread disease, or has a high probability of causing such effects.

Since a fire protection system design can vary, the level of backflow protection should be based on the type of cross-connection and the degree of hazard presented. Additionally, the local plumbing code could have further regulations affecting systems connected to private plumbing systems.

M-14 now has two general approaches for cross-connection control of automatic fire sprinkler systems. The first approach recommends a double check valve assembly (DCV) on all fire sprinkler systems, unless there is a risk of a high hazard cross-connection, in which case a reduced-pressure zone principal backflow prevention assembly (RPZ) is recommended. The second approach is to assess each type of fire suppression system individually. For this approach, M-14 provides general guidance on the various types of fire suppression systems.

Wet-Pipe Fire Sprinkler Systems, AWWA M-14 Recommendations

+4?t sprinkler systems usually have stagnated water that, in most cases, is not acceptable to drinking water standards. For new systems, a DCV is recommended on closed (non-flow-through) systems, unless there is a risk of a high hazard, in which case a RPZ or air gap is suggested. For existing wet-pipe systems with a low hazard of cross-connection, an existing modern UL-listed alarm check valve (containing no lead) can continue to be used to control the direction of flow. Existing systems that have an alarm check valve that contains lead should consider additional protection using a DCV. Consideration must be given to the hydraulic requirements of the sprinkler system if the addition of new backflow protection will decrease the pressure to the system.

Deluge Fire Sprinkler Systems, AWWA M-14 Recommendations

M-14 refers to a deluge fire sprinkler system as a dry-pipe non-pressurized fire suppression system. These systems are open to the atmosphere and generally do not require backflow protection unless chemicals will be added when water flows, in which case, a RPZ is suggested.

Dry Pipe and Preaction Fire Sprinkler Systems, AWWA M-14 Recommendations

Dry-pipe and preaction fire sprinkler systems are similar in design. A dry-pipe pressurized system is typically pressurized with air or nitrogen, whereas a preaction system may or may not be pressurized. In either case, a DCV is recommended unless there is a risk of a high hazard (e.g. chemicals), in which case a RPZ or air gap is recommended.

One- and Two-Family Residential Fire Sprinkler Systems, AWWA M-14 Recommendations

Residential fire sprinkler systems do not require backflow protection on systems that are constructed of approved potable material and are designed to flow water so it does not become stagnate. In this case, the same backflow requirements for the domestic plumbing would apply to the automatic fire sprinkler system.

Fire Department Connections, AWWA M-14 Recommendations

The fire department connection may also present a potential source of contamination based on the fire department's water supply and if additives are used. The location of the non-potable water source could potentially be an additional source for contaminates. In each case, the fire department's standard operating procedures, along with the location and/or use of non-potable water supplies, should be evaluated.

NFPA 13 Requirements

NFPA 13, Standard for the Installation of Sprinkler Systems, provides specific requirements where backflow protection is required for new or existing fire sprinkler systems. NFPA 13 requires that there must be a means provided downstream of all backflow prevention assemblies for a full flow test at the sprinkler system water demand. This flow connection ensures that the backflow prevention assembly will not restrict the required system demand in the event of an activation of the automatic fire sprinkler system. Where antifreeze solutions and backflow assemblies are utilized together, a listed expansion chamber is required to account for the pressure changes that result from the expansion and contraction of the antifreeze solution. Where backflow assemblies are required to be installed on existing systems, NFPA 13 requires a complete hydraulic analysis of the fire sprinkler system, including revised calculations and fire flow data to ensure that the system will still perform properly. Additionally, where backflow prevention assemblies are installed on sprinkler systems designed using the pipe schedule method, the added friction loss of the backflow device must be accounted for when evaluating the adequacy of the available water supply.

NFPA 20 Requirements

NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection, contains additional backflow requirements where fire pumps are utilized. Most fire pumps installed today are not of a positive displacement design, and therefore, they require a positive pressure at the inlet suction flange to the fire pump to ensure that the fire pump will receive the initial water to prime the pump. For all fire pump installations, the friction loss through a backflow assembly must be evaluated to ensure that the fire pump will have a positive pressure at the suction flange. When installed on the suction side of a fire pump, the backflow prevention assembly must be at least 10 pipe diameters away from the suction flange of the fire pump. The required 10 pipe diameters ensures that the water flow into the fire pump will not be turbulent and will be as laminar as possible. (Ideally, NFPA 20 would prefer that the required backflow prevention assembly be installed on the discharge side of the fire pump.) By installing the backflow prevention assembly on the discharge side of the fire pump, the pressure loss associated with the device can be addressed by the performance of the fire pump, and the issues of turbulence will not need to be addressed. When backflow preventers are located on the discharge side of the pump, they need to be listed for the working pressure (discharge pressure of the pump) of the system.

NFPA 25 Requirements

NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, provides the required inspection and testing requirements for backflow prevention assemblies installed on fire protection systems. It must be noted that NFPA 25 does not address the required maintenance and performance testing associated with the backflow performance of the assembly. Maintenance of the backflow prevention assembly should be in accordance with the manufacturer's instructions and any requirements of the authority having jurisdiction. NFPA 25 requires that all backflow prevention assemblies be inspected weekly or monthly where the control valves are locked or are supervised. The required testing of the backflow prevention assembly includes an annual flow test at the system demand and a backflow performance test. The backflow performance test should be completed after all forward flow tests to ensure that when the system is restored to service the cross-connection protection has been verified.

Conclusions

Hopefully, this article has provided a clear picture of where we are with the required cross-connection protection for automatic fire sprinkler systems. We have come a long way from the days where water authorities required RPZ protection for all automatic fire sprinkler systems, and where fire sprinkler designers were arguing that no protection was required for automatic fire sprinkler systems. Automatic fire sprinkler systems have established a long track record of life safety and property protection, and their impact on the entire community is significant. By working together to understand each group's issues and responsibilities, we can ensure that the fire sprinkler systems will have an adequate and reliable water supply, while the integrity of our drinking water is maintained.