28 Plumbing Systems & Design May/June 2004

FOCUS ON FIRE PROTECTION

Standpipe System Design Part 1David R. Hague, PE

Id like to clarify a few things about standpipe system layout and design. Although these systems have been around for some time, there are still some questions about how they should be designed and installed and just what is the intent of the design standard (NFPA 14-2003 Standard for the Installation of Standpipe and Hose Systems).

Types and LimitationsLets start with the basics and dis-

cuss the types of standpipe systems and their limitations. First of all, it is important to note that NFPA 14 does not require the installation of stand-pipe systems. The need to install a standpipe, or sprinkler system for that matter, resides in either a building code, state or local ordinance, Life Safety Code NFPA 101, or a similar document. Once the need for a stand-pipe system is established, NFPA 14 can then be used as a guide on how to design and install a standpipe system.

One of the more common types of standpipe systems is the Manual-Wet System, which is connected to a water supply that keeps the system lled with water at all times. This type of system does not provide the ow and pres-sure needed for reghting without re-department intervention. The re depart-ment must supplement the pressure through the re department connection in order to achieve the design pres-sure of 100 psi. The manual-wet system is limited in Section 5.4.1 of NFPA 14 to buildings that are not dened as high-rise and to areas that are not subject to freezing.

An Automatic-Wet System is con-nected to a water supply that is capa-ble of providing the needed ow and pressure for reghting automatically, without re-department intervention. Ordinarily an automatic-wet system needs a re pump to achieve the pres-sures needed. This type of system is limited to areas that are not subject to freezing.

A Manual-Dry System has no per-manently attached water supply and must rely on a re-department pumper (through the re-department connection) for the needed ow and pressure. A manual-dry system is restricted in use to buildings that are not high-rise and to areas that are subject to freezing.

An Automatic-Dry System operates much the same as a dry-pipe sprinkler system, in that it is pressurized with air and admits water to the system only when the air pressure has been relieved. An automatic-dry system is attached to a water supply that auto-matically provides the needed ow and pressure without re-department intervention.

A Semi-Automatic Dry System oper-ates similar to a deluge system by employing a deluge valve that admits water into the system after being activated

by a remote control, such as a manual release located near a hose valve. A semi-automatic dry system is attached to a water supply that automatically provides the needed ow and pressure.

All dry-type standpipe systems are limited to use in areas that are subject to freezing and further, cannot be used in high-rise buildings.

Each system type has limitations. These limitations also hold true for the system classications. Standpipe sys-tems are classied as Class I, II, or III.

A Class I system supplies 2-inch (65 mm) hose valves for re-department use. A Class II system provides 1-inch (40 mm) hose sta-

tions (complete with hose and nozzle) for use by either re-department or re-brigade personnel. This is a change in the 2003 edition of the standard where previously Class II systems were to be used by building occupants. It is important to note that it is now the intent to have building occupants exit the building in the event of a re rather than attempt to ght the re.

Class III systems are simply a combi-nation of Class I and Class II standpipe systems. In a Class III system, you may nd a 2-inch (65 mm) hose valve and a 1-inch (40 mm) hose rack on the same system. In buildings protected by an approved automatic sprinkler system, a Class III system can be pro-vided with a 2-x1-inch (65 mm x 40mm) reducer, cap, and chain in lieu of a 1-inch (40 mm) hose rack. This is important because some building codes require a Class III system for high-rise buildings. Remember, if a standpipe system has hose in a hose rack that hose must be pressure tested every three years. Such an installation, if not required, can be an unnecessary expense to the building owner.

System LayoutSystem layout is the next area for

examination with the focus on Class I

NFPA 14 does not require the installation of standpipe systems. The need to install a standpipe, or sprinkler system for that matter, resides in either a building code, state or local ordinance, Life Safety Code

NFPA 101, or a similar document.

Note: Any opinion expressed in this article is the personal opinion of the author, and does not necessarily represent the ofcial position of the NFPA or its Technical Committees. In addition, this correspondence is neither intended, nor should be relied upon, to provide professional consultation or services.

It is important to note that it is now the intent to have building occupants exit the building in the event of a re rather than attempt to ght the re.

May/June 2004 Plumbing Systems & Design 29

and III standpipes since Class II stand-pipes are not very common. First, every required exit stairway must have a standpipe hose connection. The stand-pipe should always be located in the stairway whenever possible. Doing so provides protection for the reghter and the equipment since the stairway provides a level of re resistance and in some cases positive air pressure to prevent lling the stairway with smoke. If the standpipe cannot be located in the stairway, it must be protected by a level of re resistance (or enclosed in a re-rated pipe chase) equal to that of the stairway, an added expense that can be avoided, as described above.

The maximum distance between standpipes differs based on whether the building is protected by an auto-matic sprinkler system. NFPA 14 refers to this as travel distance. For buildings with no sprinkler or partial sprinkler protection, standpipes should

be located so that a reghter does not have to travel more than 150 feet (45.7m) from any point on any oor to reach a standpipe hose connection. For a building protected throughout by an automatic sprinkler system, a reghter should not have to travel more than 200 feet (61m). If exit stairs happen to be located further than these restric-tions, an additional riser must be pro-vided. This is a case where a riser may have to be installed in a corridor or in the corner of a room and boxed-in to protect the piping.

There is also some confusion sur-rounding the interconnection of standpipes. First, standpipes must be interconnected by a common feed main from one or more water supplies. Each standpipe must have a riser isola-tion valve so that a single riser can be shut down while keeping other risers in the system operational. Sprinkler systems that are supplied by standpipe

systems (i.e., combined systems) can be connected to multiple standpipes. However, the sprinkler system cannot serve as the interconnection required by NFPA 14.

In the next article Ill discuss location of standpipe system hose connections, hydraulic calculation of standpipes, and the requirements for pressure-regulat-ing devices.

FOCUS ON FIRE PROTECTION

David Hague, PE, is Senior Fire Protection Specialist for the National Fire Protection Association, located in Quincy, Mass. He is NICET-certied in Sprinkler and Special Hazards

Systems Layout. Prior to joining NFPA, he worked as an engineering technician designing re-protection systems for the sprinkler industry.

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32 Plumbing Systems & Design July/August 2004

FOCUS ON FIRE PROTECTION

Standpipe System Design Part 2David R. Hague, PE

Part one of this article (May/June 2004 Plumbing Systems & Design, pp. 28-9) focused on the types and limita-tions of standpipe systems and system layout. It concluded with a brief discus-sion of sprinkler systems supplied by standpipe systems, noting that these sprinkler systems can be connected to multiple standpipes.

Hose-Connection LocationsThe next consideration in standpipe

system design should be hose-con-nection locations. An important aspect of hose connection location is acces-sibility. Hose connections should be located 3 to 5 feet (0.9 to 1.5m) above the floor for ease of use, and must be located at each intermediate landing between floors (or on the main land-ings when approved by the authority having jurisdiction) in stairways. Hose connections must also be available at the highest landing where stairways access the roof or on the roof where stairways do not access the roof. The roof outlet is needed to assist the fire department in fighting a roof fire.

While there is no exception to this requirement in NFPA 14, some codessuch as NFPA 5000 Building Construction and Safety Codewill allow the roof outlet to be omitted when the roof pitch exceeds 3 inches in 12 inches for specific occupancies. In my personal opinion, a roof outlet is only required above a single stairway. In other words, you are not required to provide a roof outlet for each stand-pipe even if the system consists of two or more risers.

Pipe SizingOnce the system type and layout

have been determined, it is then time to consider pipe sizing. Every stand-pipe system, whether manual or auto-matic, must be calculated to verify that the design requirements are met.

Lets consider flow first. Again, our discussion will only involve Class I and III standpipes, since Class II standpipes are not very common. The most hydraulically demanding stand-pipe must be designed to handle a flow of at least 500 gpm (1893 lpm). This flow is based on calculating 250 gpm (946 lpm) at each of the two topmost outlets. Notice I said the most hydraulically demanding, not the most remote standpipe. By saying, most demanding, I am referring to the standpipe that creates the highest demand of flow and pressure. The most demanding standpipe may not always be the one furthest from the point of supply.

For systems with more than one standpipe, an additional flow of 250 gpm (946 lpm) must be added for each standpipe. For buildings that are not sprinklered or are only partially sprin-klered, the total flow for the standpipe system is not required to exceed 1250 gpm (4731 lpm). For a building that is completely sprinklered, the standpipe system flow is not required to exceed 1000 gpm (3785 lpm).

We have defined the flow require-ments for standpipe systems. Now, lets take a look at pressure. Once again, our calculations will begin at the top-most outlet of the most hydraulically demanding standpipe. Our starting pressure must be not less than 100 psi (6.9 bar) for all systems, whether auto-matic or manual. The only difference is for an automatic system, the perma-nently attached water supply (usually a fire pump) must be capable of meeting or exceeding the system demand. For manual systems, the calculations must provide flow and pressure demand information at the fire department con-nection (FDC). Remember, in part 1 of this column I said that a manual system relies on the pressure provided by the fire department as supplied through

the fire department connection. This is why we calculate manual standpipe systems to the FDC; the FDC is our point of supply.

Frequently, standpipe and sprin-kler systems are combined or use common feedmain piping. This is a common practice and is intended to keep the costs associated with the installation of these systems as low as possible. When calculating a combined system, the sprinkler system demand must be added to the standpipe system demand only when the building is pro-vided with partial sprinkler protection. In such cases, the calculated demand must be added by 150 gpm (568 lpm) for light hazard occupancies or by 500gpm (1893 lpm) for an ordinary hazard occupancy. For buildings pro-tected in every area by an approved automatic sprinkler system, no sprin-kler demand is required to be added to the standpipe system calculations. This illustrates the ability of a sprinkler system to contain and control a fire.

In some high-rise building applica-tions, exceptionally high pressures may be needed to achieve the above referenced design requirements. First, it is important to note that system pressures are not permitted to exceed 300 psi (24.1 bar) since most listed system components are not rated for pressures higher than that. Second, pressures exceeding 175 psi (12.1 bar) can be hazardous to the firefighter. In cases such as this, pressure-regulating devicessuch as a pressure-control, pressure-reducing, or pressure-regulat-ing valvesmust be used. Depending on the exact type and manufacture, these valves will either be factory or field adjusted. It is critical that the cor-rect valve be installed in its proper place due to pressure adjustment. In the case of a field-adjusted valve, it is also critical that the adjustment be made during system commissioning.

Note: Any opinion expressed in this article is the personal opinion of the author, and does not necessarily represent the official position of the NFPA or its Technical Committees. In addition, this correspondence is neither intended, nor should be relied upon, to provide professional consultation or services.

July/August 2004 Plumbing Systems & Design 33

When pressure-regulating devices are used in a standpipe system, a drain and test riser must be installed to facilitate testing of these devices. Figure 1 illus-trates a combined sprinkler/standpipe system with an accompanying drain riser. The drain riser, in addition to serving the sprinkler system as illus-trated, must be equipped with a 2-

inch (65mm) fitting for connecting hose to the riser for testing.

Like sprinklers, stand-pipe systems must be tested prior to being placed in service. As with all water-based fire-protec-tion systems, standpipes must be hydrostatically pressure-tested to 200 psi (13.8 bar) for two hours or 50 psi (3.5 bar) in excess of the minimal static pres-sure when that static pres-sure is in excess of 150 psi (10.3 bar). In addition to

this test, a flow test at the design flow and pressure must be conducted and documented. A contractors material and test certificate for standpipe systems must be completed and submitted with the as-built drawings as part of the proj-ect closeout.

This two-part column is not intended to be a comprehensive design pro-cedure for standpipe systems, but I

thought it would be helpful to address some pertinent facts about the finer points of standpipe system design. At some point in the future, I will re-visit the topic of pressure regulating devices. I hope you find this informa-tion useful. References1. NFPA 5000 Building Construction

and Safety Code, 2002 Edition, Chapter 55 (Fire Protection Systems and Equipment).

FOCUS ON FIRE PROTECTION

David Hague, PE, is Senior Fire Protection Specialist for the National Fire Protection Association, located in Quincy, Mass. He is NICET-certified in Sprinkler and Special Hazards

Systems Layout. Prior to joining NFPA, he worked as an engineering technician designing fire-protection systems for the sprinkler industry.

Source: NFPA 14, Figure A.7.10.1.3.1(a)

Figure 1. Combined Standpipe/Sprinkler System

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