Installed Fire Protection: Water Supply and Standpipe Systems
Water supply is critical if you do not have installed fire protection systems; it becomes even more crucial if you do.
THIS article is intended to provide a brief overview of water supplies for fire protection and standpipe systems. It is not a code compliance article. For detailed requirements, check with your local authority having jurisdiction (AHJ). There are several recognized codes and standards, as well as a variety of local ordinances that may be in force in your area. A few National Fire Protection Association (NFPA) standards are listed at the end of this article for general reference.
While many substances are used for fire control, water is still the major one. Water is well suited to the task of fire extinguishing. Water cools the burning fuel, and this heat reduction extinguishes the fire. One pound of average wood generates approximately 9,000 BTUs when burned completely. One pound of water taken from 70 degrees F through its conversion to steam at 212 degrees F absorbs about 9,000 BTUs. Providing sufficient water for fire suppression is the purpose of the water supply system. Water supply is critical even if you do not have any installed fire protection systems; it becomes even more crucial if you do.
Water supply systems typically include an original source of water, water storage, distribution piping, pumps, and control valves. Water supply for fire protection covers water for use in standpipe systems (covered in this article) and other water-based fire suppression systems, which will be the topic of a future article.
Water Supplies, Valves, and Pumps
The original source for water is usually a city water main or a well on the property being protected. For large facilities, an on-site water supply is typically stored one of three ways: 1) a suction tank, 2) an elevated tank, or 3) a reservoir. The water supply must have sufficient capacity to meet all required system demands for the required duration. The specific code requirements for capacity and delivery volumes are based on the number and type of installed fire protection systems being served by the supply.
Control valves on fire protection water supplies usually are required to be the indicating type, meaning you can tell by looking at the valve whether it is open or closed. Outside screw and yoke (OS&Y) and post indicator valves (PIV) are the most common types. Most modern systems also equip valves with tamper switches that will provide a trouble alarm if the valves are closed. Water supply valves are also frequently chained and locked in the open position to prevent accidental closure. Water supply control valves should be inspected at least monthly; unlocked valves without tamper switches should be inspected weekly. A closed water supply valve is one of the more common reasons for systems failing to perform effectively.
Water supply connections to municipal water systems may require backflow preventors and meters. Backflow preventors stop any reverse flow from your fire protection water system back into the potable municipal water system. Meters, if required, are generally a special type to minimize the restriction of flow.
Many water supply systems for fire protection will be equipped with fire pumps to boost flow and pressure from the water supply. Pumps are designed to start automatically when a pressure drop or water flow is detected in the system. Small jockey pumps are often part of these systems. These small pumps take care of small pressure drops from leakage or other causes, to avoid starting the main fire pump unnecessarily.
Fire pumps require regular inspection and testing, and two types of testing are often done. To check the operation of the pump only, the test button on the fire pump control panel may be used. This will start the pump, ensuring the batteries for the starter have sufficient charge and that the pump will start and run effectively. Another, better method, I believe, is to cause a pressure drop in the system by opening a drain. This method also tests the detection portion of the pump system.
Standpipe System Operation
Standpipe systems are designed to provide fire protection water for hose lines in strategically placed locations inside a structure. They are most common in large-floor-area buildings, where much of the facility may be some distance from an outside entrance, and in multistory buildings, where getting water for hose line use to the upper floors would be difficult if not impossible from a ground-based source.
Standpipe systems fall into two major categories, manual and automatic. Manual systems provide piping throughout the building but are not equipped with a water supply. They are supplied with water by the fire department in the event of a fire. Automatic systems are connected to a water supply and capable of being supplied by the fire department.
Standpipe systems are provided with fire department connections (FDC) that allow water to be supplied to the system from a fire apparatus. This allows the fire department to increase flow and pressure in the system. The condition and accessability of FDC should be periodically inspected. It is important to ensure the threads on your FDC and standpipe outlets match the type used by your local fire department. If you have private hydrants on your property, these threads must be compatible.
Who Will Fight the Fire?
Standpipe systems are primarily divided into three classes based on the configuration of the hose stations. A Class I standpipe provides one 1 1/2-inch outlet and is equipped with hose that may be used by the occupants of the building. A Class II standpipe is equipped with a 2 1/2-inch outlet and no hose. It is intended to be used by the fire service, not building occupants. A Class III standpipe system is a combination of the first two. A 2 1/2-inch outlet is typically equipped with a reducing fitting to 1 1/2-inch hose, and the hose is then attached. The hose may be intended for use by trained occupants, but I don't generally recommend this. It is unlikely the average occupant will use this hose effectively without extensive training.
In most facilities the occupants are not provided with any training, and certainly not the extensive training required for safe and effective use. Two challenges can create issues for the occupants. First is the concern over safety. People with such a large hose, compared to the typical garden hose they may be accustomed to, tend to feel they can put out a fire of any size. This is not the case. The other issue is that they have no personal protective equipment. To fight a fire beyond the size that a fire extinguisher might control involves potential exposure to considerable heat, hazardous smoke, and fire gases.
If you have a formal fire brigade, these personnel can make use of the standpipe connections but should be supplied with higher-quality hose and nozzles than those typically installed on standpipe hose stations. The fire department definitely will bring its own hose.
Hose provided on standpipe hose stations is typically 100 feet long. Hose for installation on standpipe systems is typically inexpensive and has a thin jacket and lining. Hose must be periodically inspected and tested. The bends in the hose on a rack storage arrangement may damage the hose, so take it off the rack occasionally and re-rack with the folds at different locations. Nozzles must be the variety that are able to be closed. Hose, hose stations, and nozzles should be inspected at least quarterly.
Water supply systems provide the foundation for all water-based fire protection systems. If they are not adequate either due to design or readiness, the fire protection systems they supply will not work effectively.
Standpipe systems provide an important function to assist with manual fire control either by your own personnel or the fire department. Ensuring that you have an adequate system and that it is maintained in proper condition will contribute to controlling a fire in your facility.
References
1. "Industrial Fire Protection Handbook" 2nd edition, R. Craig Schroll, ©CRC Press 2002, ISBN: 1-58716-058-7.
2. NFPA 14 Standard for the Installation of Standpipe and Hose Systems, 2003 Edition.
3. NFPA 20 Standard for the Installation of Stationary Pumps for Fire Protection, 1999 Edition.
4. NFPA 22 Standard for Water Tanks for Private Fire Protection, 2003 Edition
5. NFPA 24 Standard for the Installation of Private Fire Service Mains and Their Appurtenances, 2002 Edition.
6. NFPA 25 Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, 2002 Edition.
7. 29 CFR 1910.158, Standpipe and hose systems.
This article originally appeared in the August 2003 issue of Occupational Health & Safety.