STANDPIPE SYSTEMS
FIRE PREVENTION BUREAU
Standpipe systems recently have been the subject of much discussion and debate. At the heart of these deliberations are some philosophical issues concerning standpipe design and use.
Let’s start with a refresher on standpipe systems. There are three types: Class I, Class II, and Class III. Class 1 standpipes are intended for fire department use, Class II for use by building occupants, and Class III for use by both the fire department and building occupants. Then there are “combined” systems, which are essentially hose valves attached to and supplied by a sprinkler system.
Building codes typically specify when a standpipe system is required and the type. These requirements are based on the size of the building and the type of occupancy.
Class I systems have 2 1/2-inch hose valves (typically without hose). Class II systems have 1 1/2-inch hose valves with 100 feet of 1 1/2-inch hose and nozzle. Class III systems have both 2 1/2-and 1 1/2-inch hose valves with 100 feet of hose and nozzle.
The 2 1/2-inch hose valves (Class I and III systems) typically are found in the following locations: in fire-rated stair enclosures: at horizontal exits; on the “floor” itself, when the travel distance to an exit exceeds certain limitations, and preferably in “protected areas” such as corridors (new to NFPA Standard 14); and at specific locations in covered mall buildings. The 1 1/2-inch hose valves (Class II and III systems) are located so that there is a hose valve within 130 feet (100 feet of hose with 30-foot stream) of all portions of the building.
Standpipe systems typically are designed under one of two standards— NFPA Standard 14 or Uniform Building Code (UBC) Standard 38-2. The latest edition of NFPA 14 (1993) was approved by the NFPA membership in November and awaits issuance by the Standards Council. The 1991 UBC Standard 38-2 is the most current edition. Both documents are similar in many respects but arc different in others, such as total water supply requirements.
MINIMUM PRESSURE
Die first philosophical issue concerns the minimum pressure the standpipe system must provide at 2 1/2-inch hose valves. For many years, firedepartments used 2 1/2-inch handlines with smooth-bore nozzles. However, since around World War II. 100-psi combination nozzles (followed by automatic nozzles) and 1 1/2-inch (followed by 1 3/4-inch) hose slowly havereplaced the “cumbersome” 2 1/2-inch handline with smooth-bore nozzle.
While thesechanges were taking place in handlines, the standpipe system itself remained virtually unchanged. Standpipes continued to be designed, as they had been for many years, to provide 250 gpm at the topmost hose valve on each riser (500 gpm from the hydraulically remoteriser) at a pressure of 65 psi. These designs were based on the use of 2 1/2-inch handlines with smooth-bore nozzles.
In essence, without the use of a fire department engine pumping into the fire department connection, these standpipe designs are inadequate to supply the 1 1/2-/1 3/4-inch handline with 100-psi combination/automatic nozzle. This is significant, especially since thousands of systems across the country are designed to these flows/pressure. A recent study indicates that only three percent of fire departments surveyed still use 2 1/2-inch handlines with smooth-bore nozzles.
This situation raises the following question: Should the standpipe standards be changed to recognize the use of the smaller handlines, or should firefighters switch back to using 2 1/2-inch handlines? This question has been debated the past few years, especially since the First Interstate fire in Los Angeles and the One Meridian Plaza fire in Philadelphia. The debate came to a head in November, when the NFPA membership approved a change to require a minimum of 100 psi for 2 1/2-inch hose valves. UBC Standard 38-2 also now requires a hose outlet pressure of 100 psi.
In my opinion, this effort does not help firefighters using 100-psi nozzles. Obviously, friction loss will take its toll—since there is only 100 psi at the standpipe hose valve, there certainly will be less than 100 psi at the nozzle. These 100-psi nozzles will be operating at below their “rated” pressure.
If your department uses 100-psi nozzles with 1 1/2or 1 3/4-inch hose for your standpipe operations, I suggest the following:
- Analyze all the standpipe systems in your jurisdiction and determine the
- flow/pressure capability of each system.
- Consider the use of 2 1/2-inch handlines with smooth-bore nozzles as a “backup” in case of problems with supplying the fire department connection, problems with pressureregulating hose valves, or other “lowpressure” problems.
- Ensure that fire department connections are unobstructed and clear of debris, hose connections are functional (and of the same fire department thread), and piping has been hydrostatically tested.
- Consider investing in lower-pressure (75-psi) combination nozzles with smooth-bore capability for primary attack line.
- I lave fire prevention personnel discuss this issue with suppression personnel.
HOSE SIZE
The 100-psi pressure issue raises another philosophical question: Are 1 1/2or 1 3/4-inch handlines adequate for fighting significant high-rise fires? Many texts specify the use of twoor 2 1/2-inch hose when attacking a wellinvolved high-rise fire. Yet, surveys have indicated that many fire departments are using 1 1/2or 1 3/4-inch hose in their standpipe packs.
This question has implications concerning the standpipe system design, especially if high flows are expected from the smaller 1 1/2or 1 3/4-inch “friction-loss-intensive” hoselines. It appears to be the proverbial situation of cramming 10 pounds of garbage into a five-pound bag.
Does an automatic or combination nozzle have the reach and penetrating capabilities of a smooth-bore nozzle when attacking a heavily involved high-rise fire? Aren’t the “straight” streams from automatic and combination nozzles just empty “cones” of water?
After reviewing several high-rise fires, it becomes apparent that 1 1/2and 1 3/4-inch attack lines just don’t have the “punch” to knock down well-involved fires. It takes a 2 1/2-inch line to do the job.
My suggestion: If you’re using 1 1/2-or 1 3/4-inch attack lines for high-rise fires, have a 2 1/2-inch line immediately available to back up the smaller line.
SYSTEM RELIABILITY
Standpipe system reliability is another topic of concern. The Fort Worth (TX) Fire Department has been conducting annual tests and inspections of all high-rise Class I and III standpipe systems (143 total) in the city since 1985. Astonishingly, the first year’s tests/inspections revealed that all of the systems were not in compliance with standpipe design and installation standards. Even more horrifying, a full one-third of the systems were not operational —they could not be used during a fire.
The Fort Worth Fire Department ordered repairs/corrections on all of the systems during the first year of tests/inspections. The following year, it saw a dramatic improvement—the number of problems dropped significantly.
Maintenance of all fire protection systems, including standpipe systems, is essential. The fire service must take an active role in ensuring that all systems are inspected and tested by competent individuals. Consider adoption of NFPA Standard 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Fro ted ion Systems.
CLASS II STANDPIPES
Should “house lines” (Class II standpipes) be used by firefighters, with the “private” hose provided for occupants? Have Class II standpipes outlived their usefulness in most applications?
I am aware of several instances in which engine companies have stretched a house line and successfully subdued the fire. However, isn’t it too risky to gamble on the use of commonly neglected and often unlined hose? (NFPA Standard 14 currently requires the use of lined 1 1/2inch hose.) Isn’t it better to disconnect the house line and connect your own hose?
(Photo by Mark Munoz.)
If you do decide to connect your own hose to a Class II system, make sure you have the proper nozzle. Most Class II standpipes are designed to provide a minimum pressure of 65 psi and are limited to a maximum 100-psi residual pressure at the hose valve. You probably will need to disengage or remove (as appropriate) the pressure-restricting device that is installed. Many Class II standpipes do not have a fire department connection to boost the water supply at the hose outlet.
It appears that the model building codes are moving toward eliminating Class II standpipes except in certain occupancies. Some government agencies have ordered the removal of the hose from existing Class I I standpipes. It has been argued that the general fire protection community no longer should expect untrained civilians to fight fires with these systems.
The response from the fire service has been somewhat mixed. Some argue for Class II standpipes, some argue against. The fire service needs to reach a consensus on this issue.
SPRINKLER SUPPLY ONLY
If Class I/I II standpipes are provided in a fully sprinklered building, can the water supply to the system meet just the sprinkler demand? In other words, can a building’s fire pump and water supply be sized (with certain minimum riser sizes) to accommodate only the sprinkler demand, which may be only a few hundred gallons per minute at, say, 40 psi?
There’s much debate on this issue. Some argue that by requiring a large water supply (on the order of 1,250 gpm to 2,500 gpm for the system), sprinkler system installations are discouraged. Others argue that a standpipe is a “stand-alone” system and that by putting all the “eggs” in the sprinkler basket, individuals are flirting with danger (I have heard it said that three floors of the Sears Tower in Chicago are without sprinkler protection on any given day because of remodeling). The “sprinkler-supplyonly” allowance has been discussed most actively in building code organizations.
As a related note, the 1993 NFPA 14 standard has reduced the maximum total water supply requirements for sprinklered buildings from 2,500 gpm to 1,000 gpm (or the sprinkler and hose stream demand, whichever is greater). The maximum water supply for unsprinklered buildings is 1,250 gpm.
I believe that reducing the water supply requirements to just the sprinkler demand puts too much reliance on the sprinkler system. Certainly, sprinkler systems have an overall success rate of greater than 97 percent. However, I believe that in a fire on the upper floors of a high-rise, a frilly supplied standpipe is essential for all eventualities. How about those very tall buildings that are beyond the pumping capabilities of an engine company in the street?
Obviously, fire department connections are critical to supply the standpipe when a sprinkler-only water supply is provided. Your department must ensure that they are serviceable at all times.
PRESSURE-REGULATING DEVICES
For several years, some design standards actually limited 2 1/2-inch hose outlet residual pressures to 100 psi unless higher pressures were approved by the fire department. It is likely that some Class I/III standpipes were installed with the 100-psi pressure limitation without asking the local fire department about its preference. (One of our San Antonio, Texas, fire inspectors recently found pressure-reducing 2 1/2-inch hose valves on the center stairwell riser of a threeriser system in a five-story building!)
The new 1993 NFPA 14 standard now requires static/residual pressure reduction to 175 psi on 2 1/2-inch hose valves when the static pressure exceeds 175 psi. This standard also requires a three-inch test drain for standpipe systems using pressure-regulating devices to periodically test the pressure-regulating valves and ensure their proper operation/setting
The following steps can help ensure successful standpipe operations:
- Analyze your current standpipeoperations, including equipment and procedures. Establish the maximum amount of water you want to flow from each line. Determine the required pressures and flows needed from the hose valve on the riser.
- Study the existing standpipe systems in your jurisdiction. Know their capabilities, their limitations, and the maximum and minimum pressures from each hose valve. If your standpipe pack and/or procedures don’t match the standpipe systems, something must change—take remedial action.
- Make sure new systems are properly designed, installed, and tested. Make sure all systems are periodically and properly tested/inspected/maintained under close fire department supervision. Require corrections where deficiencies are noted.
