Informal Interpretations Offer Assistance on Standpipes
The informal interpretations featured here address standpipes. AFSA’s informal interpretations are provided to AFSA members by Vice President of Engineering & Technical Services Roland Huggins, P.E. and Manager of Fire Protection Engineering Tom Wellen, P.E. These opinions are provided for the benefit of the requesting party, and are provided with the understanding that AFSA assumes no liability for the opinions or actions taken on them.
Subject: Standpipes and Hydrostatic Tests Including the FDC
QUESTION: “Section 18.104.22.168 calls for the two-hour hydrostatic test at 200 psi for two hours for all manual dry standpipes and semi automatic dry standpipes, including piping in the fire department connection (FDC). Is it the intent for this statement to apply to all FDCs or just the ones connected to the dry standpipe?”
ANSWER: In response to your question we have reviewed NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, 2014 edition as the applicable standard. Our informal interpretation is that all FDCs require a hydrostatic test every five years. Section 22.214.171.124.1 clarifies that manual wet standpipes that are part of a combined sprinkler/standpipe system shall not be required to be tested in accordance with 126.96.36.199. This information is located in Chapter 6 for Standpipe and Hose Systems and would not apply to other chapters. The other chapters have same requirement for hydrostatic testing of the FDCs. This changed in the 2014 edition where new text was added as Section 13.7.4 that states,
“The piping from the fire department connection to the fire department check valve shall be hydrostatically tested at 150 psi for two hours at least once every five years.” The substantiation used is that the piping is dry and subject to corrosion that could lead to a potential failure. The 150-psi pressure is specified since that is the operating pressure used to support systems by the responding fire department. Table 13.8.1 addresses hydrostatic tests for FDCs in the summary of component replacement action requirement tables. The requirement is to isolate and hydrostatic test for two hours at 150 psi or 50 psi above the normal working pressure (200 psi minimum) when FDC components or piping were replaced.
Subject: Minimum Standpipe Size
QUESTION: “We have a project where the standpipes are a combination standpipe as the floor control assemblies come off of the standpipe at each floor. The Authority Having Jurisdiction (AHJ) has stated that per NFPA 14, Standard for the Installation of Standpipe and Hose Systems, Section 7.6.2 that all combination standpipes are to be a minimum size of 6 in. Is that correct?”
ANSWER: In response to your question we have reviewed the 2016 edition of NFPA 14 as the applicable standard. Our informal interpretation is that the minimum size for a standpipe is 4 in. for hydraulically calculated systems where the building is protected throughout by an approved automatic sprinkler system. Section 188.8.131.52 specifically indicates that the minimum size for a standpipe is 4 in. when the sprinkler system is installed to NFPA 13, Standard for the Installation of Sprinkler Systems, or NFPA 13R, Standard for the Installation of Sprinkler Systems in Low-Rise Residential Occupancies. It also confirms that the statement “protected throughout” means when installed in accordance with NFPA 13 or 13R. Section 184.108.40.206 applies whether the standpipe is combined or not combined. For example, if the sprinkler systems have feeds separate from the hydraulically calculated standpipe and the building is sprinklered throughout, the minimum size of the standpipe can be 4 in. This is the reason the word “combined” is not included in 220.127.116.11. Section 18.104.22.168 is an exception to the requirement of Section 7.6.2. This was confirmed in the exception format in the 2000 edition under Section 5.6.2. In a building that is not sprinklered throughout, the minimum size for a combined standpipe is 6 in. according to Section 7.6.2. In addition, the standard indicates that you do not have to add the flows from the sprinkler demand unless there is partial sprinkler protection according to Section 22.214.171.124.2. This section indicates to use the flow rates from 7.10.1 and increase by an amount equal to the hydraulically calculated sprinkler demand or 150 gpm for light hazard or 500 for ordinary hazard, whichever is less. The standpipe size can be 4 in. if the hydraulic calculations support the design when sprinklers are provided throughout the building. The standpipe and fire sprinkler flows are not combined in the hydraulic calculations.
Subject: Roof Outlet Piping Arrangement
QUESTION: “In Figure A.126.96.36.199, a nonrising stem gate valve is depicted. Is the depicted control valve required in areas not subject to freezing conditions? Where are the requirements for this control valve being installed in this standard?”
ANSWER: In response to your questions we have reviewed NFPA 14, 2016 edition as the applicable standard. Our informal interpretation is that the control valve is not needed if the application is not subject to freezing conditions. Figure A.188.8.131.52 is just an example of an arrangement for piping a hose outlet to the roof. This is not intended to require this exact piping arrangement for every hose outlet located on a roof. For example, some buildings have stair access to the roof. The outlet(s) is located either within the stair tower or on the exterior wall of the stairwell. A control valve is added so the piping exposed to freezing conditions can be isolated and remain dry. If needed, a ball drip is added to remove any residual water from the piping. The control valve is not desired in areas not subject to freezing. An arrangement without a control valve would actually expedite firefighting Sprinkler Age | July/August 2016 41 operations since the hose valve would be charged with water. Regarding the control valve for the roof outlet, the references in Section 6.3.2 and 6.3.3 do not specifically address the control valve for the roof hose outlet. Section 6.3.2 states, “Valves shall be provided on all standpipes, including manual-dry standpipes, to allow isolation of a standpipe without interrupting the supply to other standpipes from the same source of supply.” This is for a valve typically at the bottom of the standpipe as it relates to the supply main. Section 6.3.3 states, “Listed indicating-type valves shall be provided at the standpipe for controlling branch lines where the distance to the remote hose station exceeds 40 ft measured along the pipe.” The roof hose valve is not typically considered a branch line since the piping extends vertically through the roof where Section 6.3.3 would not be applicable.
Subject: Working Pressure of Steel Pipe
QUESTION: “I have a high-rise standpipe with pressures above 300 psi. NFPA 13 and 14 references pipe up to 300 psi in accordance with its listing. Most of the manufacturers carry a listing up to 300 psi for sprinkler pipe. When pressures are over the 300 psi listing, is it acceptable to apply the actual ASTM standards for the actual pipe pressure rating for pressures in excess of 300 psi?”
ANSWER: In response to your question we have reviewed the 2016 editions of NFPA 13 and NFPA 14 as the applicable standards. Our informal interpretation is that steel pipe pressures are limited to 300 psi. The working pressures of steel pipe published by the manufacturers have values that exceed 300 psi. When the pipe is used for fire sprinkler applications, they indicate a working pressure up to 300 psi. The joining method and the wall thickness has an impact on the working pressure per Sections 6.3.2 for welded and roll-grooved connections and Section 6.3.3 for threaded connections. An exception to this is Section 6.3.4 for specially listed steel pipe. NFPA 14 has similar wording as Sections 4.2.3, 4.2.4, and 4.2.6. Listed pipe for higher working pressures will be needed when the required pressure exceeds 300 psi. We do not know who has listed pipe in excess of the 300-psi pressure. A design modification may have to be made if pipe listed for higher pressures are not found such as the use of multiple pressure zones. NFPA 14 does say in Section 7.2.2 that express mains supplying higher standpipe zones shall be permitted to be designed with pressures in excess of 350 psi in accordance with their materials listings “or as approved by the AHJ” where there are no hose outlets per Section 184.108.40.206. The Stationary Fire Pumps Handbook has commentary regarding this subject on standpipes. It states, “The 1993 edition of NFPA 14 eliminated the height limitation in favor of a logical pressure limitation of 350 psi, based on the pressure ratings of available devices at the time. For the 2010 edition of NFPA 14, the Technical Committee on Standpipes opted for a performance-based approach for express mains supplying higher standpipe system zones. This performance-based approach referenced manufacturers’ pressure listings for components rather than a prescriptive pressure limitation, thus permitting pressures in excess of 350 psi. Regardless of the exact pressure requirement in the standard, most system components are listed based on 300 psi.” As such, discuss this with the local AHJ for pressures exceeding 300 psi.
Subject: Standpipe Calculations for Separated Occupancies
QUESTION: “We have a 23-story high-rise condominium attached to a seven-story parking garage that is separated by a two-hour firewall. The condominium is protected throughout with sprinklers and the parking garage is not protected. The high-rise standpipes are automatic wet and the parking garage is automatic dry. The International Building Code (IBC), 2015 edition in Table 707.3.10 indicates that a two-hour separation is acceptable to consider the two occupancies as two separate fire areas. Can the standpipes in the high-rise and the parking garage be calculated separately?”
ANSWER: In response to your question we have reviewed NFPA 14, 2016 edition as the applicable standard as well as the 2015 edition of the IBC. Our informal interpretation is that calculations are completed separately since the standpipes are in two fire areas. NFPA 14 in Section 220.127.116.11 for flow rates of Class I and Class III systems has annex material as A.18.104.22.168 that states, “If a water supply system supplies more than one building or more than one fire area, the total supply can be calculated based on the single building or fire area requiring the greatest number of standpipes.” The building codes will determine whether the application is a separate building or fire area. This is determined by distance or by a fire rated separation. Regarding fire area, NFPA 14 references this as an area of a floor in annex A.7.1. The IBC actually defines a fire area in Section 902.1 as, “The aggregate floor area enclosed and bounded by fire walls, fire barriers, exterior walls or horizontal assemblies of a building. Areas of the building not provided with surrounding walls shall be included in the fire area if such areas are included within the horizontal projection of the roof or floor next above.” As such, NFPA 14 is straightforward that the condominium has a separate calculation from the parking garage. They are separated occupancies per Section 508.4 of the IBC so they do not need to be combined. On a related note, it is worth discussing interconnection of the standpipes. NFPA 14, 2010 edition, made a clarification by adding new text that also indicates in A.7.5 that standpipe systems in separate buildings or structures fed by the same water supply are not required to be interconnected. This section does not use fire areas as a determining factor as shown in 22.214.171.124 since a single structure can have two fire areas. The term structure in this context is easier to understand if one focuses on the structural members. If a single building has two fire areas and each fire area is built using their own or separate structural members, then they are not required to be interconnected. If they are not interconnected, they are individual systems using a common supply main. As individual systems, they are not required to use the same supply. This would allow the condominium to be an automatic wet system and the garage (per Section 905.3.1 of the IBC) to be a manual dry system.
EDITOR’S NOTE: These interpretations were prepared by AFSA’s Technical Services Department in answer to specific questions from contractors and/or AHJs. These opinions are provided for the benefit of the requesting party, and are provided with the understanding that AFSA assumes no liability for the opinions or actions taken on them. AFSA members can access over 4,400 informal interpretations online. Visit firesprinkler.org.