Fire water supply - Revision history

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← Older revision		Revision as of 18:14, 2 November 2026
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	== Sources of water ==		== Sources of water ==
	Water can come from several kinds of source. In the United States, a wet standpipe system needs a direct connection to an automatic water supply. Examples are a city water distribution system, a tank and pump, an elevated tank or a pressure tank.<ref name="HO-21" /> Sprinkler systems draw on the same kinds of source. NFPA 13, the US sprinkler standard of the National Fire Protection Association (NFPA), refers to separate standards for the supply components. These are NFPA 14 for standpipes, NFPA 20 for fire pumps, NFPA 22 for water tanks and NFPA 24 for private fire service mains.<ref name="FL-73">Fleming (2002), p. 4-73.</ref>		Water can come from several kinds of source. In the United States, a wet standpipe system needs a direct connection to an automatic water supply. Examples are a city water distribution system, a tank and pump, an elevated tank or a pressure tank.<ref name="HO-21" /> Sprinkler systems draw on the same kinds of source. NFPA 13, the US sprinkler standard of the National Fire Protection Association (NFPA), refers to separate standards for the supply components. These are NFPA 14 for standpipes, NFPA 20 for fire pumps, NFPA 22 for water tanks and NFPA 24 for private fire service mains.<ref name="FL-73">Fleming (2002), p. 4-73.</ref>

			[[File:fse-fire-water-supply-v1.svg\|thumb\|upright=1.5\|alt=Schematic of a building fed by a street main and a roof tank, with fire pump, riser, sprinklers, hose reel, street hydrant and fire service connection.\|Typical parts of a fire water supply for a multistorey building. Based on Fleming (2002), pp. 4-82 to 4-83, Hopkins et al. (2005), p. 21 and Evans et al. (2005), pp. 14 and 18.]]

	If not enough water is available at a suitable pressure, a stored water supply becomes necessary.<ref name="FL-82" /> The basic choice is between an elevated (gravity) tank, a pressure tank, or a suction tank combined with a pump.<ref name="FL-83" /> Without a pump, the energy for the system must come from the height of a gravity tank or from the air pressure in a pressure tank.<ref name="FL-83" />		If not enough water is available at a suitable pressure, a stored water supply becomes necessary.<ref name="FL-82" /> The basic choice is between an elevated (gravity) tank, a pressure tank, or a suction tank combined with a pump.<ref name="FL-83" /> Without a pump, the energy for the system must come from the height of a gravity tank or from the air pressure in a pressure tank.<ref name="FL-83" />
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	== Flow, pressure and duration ==		== Flow, pressure and duration ==
	A water supply is assessed by testing it. Each test gives at least two values: the static pressure without flow and the residual pressure while a known flow is taken.<ref name="FL-81" /> The static pressure is read from a gauge on a hydrant. The residual pressure is read on the same gauge while water flows from another hydrant, preferably downstream.<ref name="FL-81" />		A water supply is assessed by testing it. Each test gives at least two values: the static pressure without flow and the residual pressure while a known flow is taken.<ref name="FL-81" /> The static pressure is read from a gauge on a hydrant. The residual pressure is read on the same gauge while water flows from another hydrant, preferably downstream.<ref name="FL-81" />

			[[File:fse-fire-water-supply-v2.svg\|thumb\|upright=1.5\|alt=Two hydrants on a water main: the first with a pressure gauge, the second, downstream, discharging water measured with a pitot tube.\|Water supply test: the gauge on one hydrant reads the static pressure with no flow and the residual pressure while a downstream hydrant flows. Based on Fleming (2002), p. 4-81.]]

	The static pressure reflects elevated tanks and running pumps, while the drop to the residual pressure reflects friction losses in the pipes.<ref name="FL-81" /> Because friction loss grows with the flow to the power 1.85, the two points can be drawn as a straight line on special graph paper. This line, the water supply curve, gives the available pressure at any flow.<ref name="FL-81" />		The static pressure reflects elevated tanks and running pumps, while the drop to the residual pressure reflects friction losses in the pipes.<ref name="FL-81" /> Because friction loss grows with the flow to the power 1.85, the two points can be drawn as a straight line on special graph paper. This line, the water supply curve, gives the available pressure at any flow.<ref name="FL-81" />
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	=== Worked example ===		=== Worked example ===
	Two 5,000 gal tanks and a 5,000 gal standpipe reserve tank on the 110th floor of each World Trade Center tower supplied the booster pump for the highest sprinkler zone. Their combined capacity was 15,000 gal (56.8 m³).<ref name="EV-18" /><ref name="EV-19">Evans et al. (2005), p. 19.</ref> The fire pump was rated at 500 gpm (1,893 L/min), and the maximum permissible flow was 150 % of that, 750 gpm (2,839 L/min).<ref name="EV-19" /> Rearranging the relation gives the duration of supply:		Two 5,000 gal tanks and a 5,000 gal standpipe reserve tank on the 110th floor of each World Trade Center tower supplied the booster pump for the highest sprinkler zone. Their combined capacity was 15,000 gal (56.8 m³).<ref name="EV-18" /><ref name="EV-19">Evans et al. (2005), p. 19.</ref> The fire pump was rated at 500 gpm (1,893 L/min), and the maximum permissible flow was 150 % of that, 750 gpm (2,839 L/min).<ref name="EV-19" /> Rearranging the relation gives the duration of supply:

			[[File:fse-fire-water-supply-v3.svg\|thumb\|upright=1.5\|alt=Falling curve of supply duration against flow for a 56.8 m3 tank, with marked points 30 min at 1,893 L/min and 20 min at 2,839 L/min.\|Duration of a 56.8 m³ (15,000 gal) stored supply as a function of the demand, t = V/Q. Based on Evans et al. (2005), pp. 18 to 19.]]

	<math display="block">t = \frac{V}{Q} = \frac{56.8\ \mathrm{m^3}}{1.893\ \mathrm{m^3/min}} = 30\ \mathrm{min}</math>		<math display="block">t = \frac{V}{Q} = \frac{56.8\ \mathrm{m^3}}{1.893\ \mathrm{m^3/min}} = 30\ \mathrm{min}</math>
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	== Reliability and redundancy ==		== Reliability and redundancy ==
	Several common causes of sprinkler failure lie in the water supply. The US Nuclear Regulatory Commission (NRC) lists a closed water supply valve, a broken supply header, an empty water tank and a fire pump that fails to start among the causes.<ref name="IS-10-2" /> An electric pump can fail through a power failure, and a diesel pump through poor maintenance, dead batteries or lack of fuel.<ref name="IS-10-2" /> The Australian data sheets summarise US statistics by Ahrens. A system that was shut off accounted for 59 % of the cases in which a sprinkler system failed to operate. When systems did operate but were ineffective, 30 % of the cases involved not enough water being discharged.<ref name="AH-79">Ahrens (2017), as cited in Australian Building Codes Board (2020a), Data Sheet C2, p. 79.</ref>		Several common causes of sprinkler failure lie in the water supply. The US Nuclear Regulatory Commission (NRC) lists a closed water supply valve, a broken supply header, an empty water tank and a fire pump that fails to start among the causes.<ref name="IS-10-2" /> An electric pump can fail through a power failure, and a diesel pump through poor maintenance, dead batteries or lack of fuel.<ref name="IS-10-2" /> The Australian data sheets summarise US statistics by Ahrens. A system that was shut off accounted for 59 % of the cases in which a sprinkler system failed to operate. When systems did operate but were ineffective, 30 % of the cases involved not enough water being discharged.<ref name="AH-79">Ahrens (2017), as cited in Australian Building Codes Board (2020a), Data Sheet C2, p. 79.</ref>

			[[File:fse-fire-water-supply-v4.svg\|thumb\|upright=1.5\|alt=Bar chart of why sprinklers failed to operate: shut off 59 %, manual intervention 17 %, maintenance 10 %, damage 7 %, wrong system 7 %.\|Causes of sprinkler systems failing to operate in US fires, as summarised in the Australian data sheets. Based on Ahrens (2017), as cited in Australian Building Codes Board (2020a), Data Sheet C2, p. 79.]]

	The [[reliability of fire protection systems]] therefore depends strongly on valves and their management. An Australian fault tree study of sprinkler systems in high-rise offices found reliabilities between 86.6 % and 97.9 %. Shutting off sprinkler zones during tenancy changes was one of the main factors in failure.<ref name="MT-81">Moinuddin and Thomas, as cited in Australian Building Codes Board (2020a), Data Sheet C2, p. 81.</ref> According to the fault tree analysis, a zone isolation valve for each floor could reduce the failure probability by 10 % to 63 % of its original value.<ref name="MT-81" />		The [[reliability of fire protection systems]] therefore depends strongly on valves and their management. An Australian fault tree study of sprinkler systems in high-rise offices found reliabilities between 86.6 % and 97.9 %. Shutting off sprinkler zones during tenancy changes was one of the main factors in failure.<ref name="MT-81">Moinuddin and Thomas, as cited in Australian Building Codes Board (2020a), Data Sheet C2, p. 81.</ref> According to the fault tree analysis, a zone isolation valve for each floor could reduce the failure probability by 10 % to 63 % of its original value.<ref name="MT-81" />

Daan: FSE wiki: Write out abbreviations at first use (NFPA, NIST, NRC, WTC, AFFF, PMMA) (written by Claude Opus 5.5)

2026-11-01T22:58:52Z

FSE wiki: Write out abbreviations at first use (NFPA, NIST, NRC, WTC, AFFF, PMMA) (written by Claude Opus 5.5)

Daan: New FSE wiki article: Fire water supply (written by Claude Opus 5.5)

2026-11-01T22:50:52Z

New FSE wiki article: Fire water supply (written by Claude Opus 5.5)

New page

A '''fire water supply''' is the source, storage and distribution of the water that sprinkler systems, hydrants, risers and hoses need to fight a fire. It can come from a public water main, from tanks on site, or from pumps that draw on either of them.<ref name="HO-21">Hopkins et al. (2005), p. 21.</ref><ref name="FL-83">Fleming (2002), p. 4-83.</ref> Its strength is described by how much water it can deliver, at what pressure, and for how long. Fleming calls the strength of the water supply the key to whether it will adequately serve a [[sprinkler system]].<ref name="FL-81">Fleming (2002), p. 4-81.</ref>

The supply serves two groups of users. Automatic systems such as sprinklers need water at once and without human action.<ref name="HO-21" /> The fire service needs water at the building for its hoses, from a [[fire hydrant]], from a riser inside the building or from its own pumping appliances.<ref name="EV-18">Evans et al. (2005), p. 18.</ref><ref name="MBIE-54">Ministry of Business, Innovation and Employment (2025b), p. 54.</ref>

In New Zealand, Building Code clause C5.5, as reproduced in C/VM2 (second edition, 2025), requires buildings to be provided with the means to deliver water for firefighting to all parts of the building.<ref name="MBIE-53">Ministry of Business, Innovation and Employment (2025b), p. 53.</ref> A water supply can also be a single point of failure. A closed valve, an empty tank or a pump that does not start can disable every system that depends on it.<ref name="IS-10-2">Iqbal and Salley (2004), p. 10-2.</ref> Redundant supply paths and independent sources are used to reduce this dependence.<ref name="EV-32">Evans et al. (2005), p. 32.</ref><ref name="MBIE-44">Ministry of Business, Innovation and Employment (2025b), p. 44.</ref>

== Sources of water ==
Water can come from several kinds of source. In the United States, a wet standpipe system needs a direct connection to an automatic water supply. Examples are a city water distribution system, a tank and pump, an elevated tank or a pressure tank.<ref name="HO-21" /> Sprinkler systems draw on the same kinds of source. The US sprinkler standard NFPA 13 refers to separate standards for the supply components. These are NFPA 14 for standpipes, NFPA 20 for fire pumps, NFPA 22 for water tanks and NFPA 24 for private fire service mains.<ref name="FL-73">Fleming (2002), p. 4-73.</ref>

If not enough water is available at a suitable pressure, a stored water supply becomes necessary.<ref name="FL-82" /> The basic choice is between an elevated (gravity) tank, a pressure tank, or a suction tank combined with a pump.<ref name="FL-83" /> Without a pump, the energy for the system must come from the height of a gravity tank or from the air pressure in a pressure tank.<ref name="FL-83" />

Elevation adds or removes pressure at 0.433 psi per foot, or 0.099 bar per metre.<ref name="FL-80">Fleming (2002), p. 4-80.</ref> The pressure of a gravity tank must therefore be calculated from the lowest expected water level, which is normally the level at which the tank counts as empty.<ref name="FL-83" /> A pressure tank must contain enough air to push out the last water at an adequate pressure. A common rule of thumb has been one-third air at a minimum pressure of 75 psi (5.17 bar), but this rule does not hold for systems with high pressures.<ref name="FL-83" />

Fire pumps make up for a lack of pressure where enough water is available at a suitable suction pressure.<ref name="FL-82">Fleming (2002), p. 4-82.</ref> Plumbing codes sometimes set a minimum suction pressure of 10 to 20 psi (0.69 to 1.38 bar).<ref name="FL-82" /> Listed fire pumps have diesel or electric drivers and capacities from 25 to 5,000 gpm (95 to 18,927 L/min). The most common sizes lie between 250 and 2,500 gpm (946 to 9,463 L/min).<ref name="FL-82" /> NFPA 20 requires each horizontal fire pump to deliver at least 100 % of its rated pressure at its rated flow and at least 65 % of that pressure at 150 % of the flow. With no flow, the pressure must not exceed 140 % of the rated pressure.<ref name="FL-82" />

The World Trade Center complex in New York shows how these elements are combined in a large building. Its primary supply was a 12 in. fire main that looped the complex and was fed from the municipal supply by two redundant 16 in. connections.<ref name="EV-14">Evans et al. (2005), p. 14.</ref> Each tower had reserve tanks of 5,000 gal (about 19 m³) on several mechanical floors, and the tanks on the 41st floor had automatic fill lines from the domestic water system. Twelve fire pumps moved the water up the building.<ref name="EV-18" /> Fire department engines could also pump water from street hydrants into the buildings through 32 fire department connections at 14 locations.<ref name="EV-18" />

== Flow, pressure and duration ==
A water supply is assessed by testing it. Each test gives at least two values: the static pressure without flow and the residual pressure while a known flow is taken.<ref name="FL-81" /> The static pressure is read from a gauge on a hydrant. The residual pressure is read on the same gauge while water flows from another hydrant, preferably downstream.<ref name="FL-81" />

The static pressure reflects elevated tanks and running pumps, while the drop to the residual pressure reflects friction losses in the pipes.<ref name="FL-81" /> Because friction loss grows with the flow to the power 1.85, the two points can be drawn as a straight line on special graph paper. This line, the water supply curve, gives the available pressure at any flow.<ref name="FL-81" />

The required flow and pressure come from a [[hydraulic calculation]] of the system. For an adequate design, the system demand point, including the allowance for fire service hoses, must lie below the water supply curve.<ref name="FL-81" /> Outside the design area of a sprinkler system, no flow is added other than the hose stream allowances.<ref name="FL-75">Fleming (2002), p. 4-75.</ref> For standpipes, US practice based on NFPA 14 (2000) requires 500 gpm (1,893 L/min) at 100 psi (6.9 bar) at the hydraulically most remote standpipe. Each additional standpipe adds 250 gpm (946 L/min), up to a maximum of 1,250 gpm (4,732 L/min).<ref name="HO-20">Hopkins et al. (2005), p. 20.</ref>

Duration is the third requirement. Tanks must be sized to provide the minimum durations set by NFPA 13 or another applicable standard, and the required pressure must still be available when the tank is nearly empty.<ref name="FL-83" /> The stored volume follows from the flow and the duration:

<math display="block">V = Q \times t</math>

{| class="wikitable"
|+ Symbols
! Symbol !! Description !! Unit
|-
| <math>V</math> || usable stored water volume || m³ (or L)
|-
| <math>Q</math> || water demand (flow) of the systems supplied || m³/min (or L/min)
|-
| <math>t</math> || required duration of supply || min
|}

The relation assumes a constant demand and no refill during the fire. Any automatic refill, for example from the public main, lengthens the actual duration. The volume is the usable volume above the level at which the tank counts as empty.<ref name="FL-83" /><ref name="EV-18" />

=== Worked example ===
Two 5,000 gal tanks and a 5,000 gal standpipe reserve tank on the 110th floor of each World Trade Center tower supplied the booster pump for the highest sprinkler zone. Their combined capacity was 15,000 gal (56.8 m³).<ref name="EV-18" /><ref name="EV-19">Evans et al. (2005), p. 19.</ref> The fire pump was rated at 500 gpm (1,893 L/min), and the maximum permissible flow was 150 % of that, 750 gpm (2,839 L/min).<ref name="EV-19" /> Rearranging the relation gives the duration of supply:

<math display="block">t = \frac{V}{Q} = \frac{56.8\ \mathrm{m^3}}{1.893\ \mathrm{m^3/min}} = 30\ \mathrm{min}</math>

At the maximum flow of 2.839 m³/min, the same tanks last 20 minutes. NIST gives the same values: a minimum of 30 minutes at 500 gpm, without any supplemental water from the domestic system, and 20 minutes at 750 gpm.<ref name="EV-19" /> Fleming's example for a pressure tank shows the same logic. A 30-minute supply for a demand of 140 gpm (530 L/min) requires at least 4,200 gal (15.9 m³) of water, plus the air needed to keep the pressure up.<ref name="FL-83" />

Hydraulic calculations by NIST for the light hazard sprinkler systems of the towers gave delivered densities of 0.10 to 0.27 gpm/ft² with up to 16 open sprinklers. The primary water supply could maintain these flows for about 10 to 89 minutes, depending on the location and number of open sprinklers.<ref name="EV-32" /> NIST concluded that the storage tanks gave enough duration for normally expected fires to allow the fire department to respond and supplement the supply.<ref name="EV-40">Evans et al. (2005), p. 40.</ref>

== Water for the fire service ==
The fire service draws its water from hydrants, from risers and from its own vehicles. In a fire engineering analysis, the time to set up a water supply is one of the steps in the fire brigade intervention model of the International Fire Engineering Guidelines.<ref name="IFEG-2.9-5">National Research Council of Canada et al. (2005), p. 2.9-5.</ref> The amount of firefighting water available at the scene is one of the resources to be assessed.<ref name="IFEG-1.9-5">National Research Council of Canada et al. (2005), p. 1.9-5.</ref> If the water supply or the number of firefighters is insufficient for interior firefighting, the strategy may change from offensive, fighting the fire, to defensive, stopping its spread to neighbouring buildings.<ref name="IFEG-2.9-4">National Research Council of Canada et al. (2005), p. 2.9-4.</ref>

National rules set the facilities. In Australia, Table 2.8 of the Fire Safety Verification Method Standard 2022 requires external fire hydrants for all buildings in the fire brigade intervention scenario. Internal hydrants are required in sprinklered buildings if any point is more than 100 m away or the building has more than three levels, and in unsprinklered buildings from 70 m.<ref name="ABCB-16">Australian Building Codes Board (2022), p. 16.</ref> The scenario applies only to buildings within 50 km road travel of a fire station.<ref name="ABCB-15">Australian Building Codes Board (2022), p. 15.</ref> In New Zealand, C/VM2 (second edition, 2025) accepts water from a pumping appliance parked so that any point in the building lies within 75 m, about three hose lengths. Otherwise an internal hydrant to NZS 4510 is needed.<ref name="MBIE-54" />

Inside tall buildings, risers bring the water to the floors. Standpipe systems are classed as wet, damp or dry by their water supply. Wet systems are filled with water at all times, while manual [[Dry and wet risers|dry standpipes]] have only fire department connections and no automatic supply.<ref name="HO-21" /> Removing the need for long hose lays from the fire engine to an upper floor improves the initial attack.<ref name="HO-21" /> For Dutch indoor car parks, NIPV notes that a dry riser can shorten the attack time, because less hose has to be rolled out.<ref name="NIPV-66">Van der Graaf et al. (2021/2023), p. 66.</ref>

Occupants can use the same water. The International Fire Engineering Guidelines mention suppression by building occupants with extinguishers and a [[hose reel]].<ref name="IFEG-1.7-1">National Research Council of Canada et al. (2005), p. 1.7-1.</ref> The New York City building code had no requirement for fire extinguishers, because it required occupant hose reels.<ref name="LE-151">Lew et al. (2005), p. 151.</ref> In WTC 7, hose reels were located in the stair enclosures, with hose cabinets throughout the floors.<ref name="HO-128">Hopkins et al. (2005), p. 128.</ref>

== Reliability and redundancy ==
Several common causes of sprinkler failure lie in the water supply. The NRC lists a closed water supply valve, a broken supply header, an empty water tank and a fire pump that fails to start among the causes.<ref name="IS-10-2" /> An electric pump can fail through a power failure, and a diesel pump through poor maintenance, dead batteries or lack of fuel.<ref name="IS-10-2" /> The Australian data sheets summarise US statistics by Ahrens. A system that was shut off accounted for 59 % of the cases in which a sprinkler system failed to operate. When systems did operate but were ineffective, 30 % of the cases involved not enough water being discharged.<ref name="AH-79">Ahrens (2017), as cited in Australian Building Codes Board (2020a), Data Sheet C2, p. 79.</ref>

The [[reliability of fire protection systems]] therefore depends strongly on valves and their management. An Australian fault tree study of sprinkler systems in high-rise offices found reliabilities between 86.6 % and 97.9 %. Shutting off sprinkler zones during tenancy changes was one of the main factors in failure.<ref name="MT-81">Moinuddin and Thomas, as cited in Australian Building Codes Board (2020a), Data Sheet C2, p. 81.</ref> According to the fault tree analysis, a zone isolation valve for each floor could reduce the failure probability by 10 % to 63 % of its original value.<ref name="MT-81" />

Redundancy reduces the dependence on a single source. In New Zealand, C/VM2 (second edition, 2025) states that a sprinkler system with two independent supplies, of which only one may depend on a town's main, has a very high degree of reliability. Such a system, with a Class A or Class B2 water supply to NZS 4541, can alone satisfy clause C3.6, which limits the radiation received at the relevant boundary.<ref name="MBIE-43">Ministry of Business, Innovation and Employment (2025b), p. 43.</ref><ref name="MBIE-44" /> The World Trade Center towers were supplied from loops at two remote locations, with isolation valves that allowed either main to operate independently.<ref name="EV-30">Evans et al. (2005), p. 30.</ref> WTC 7, by contrast, was fed by two mains within 12 ft (3.7 m) of each other from the same city main.<ref name="EV-30" />

Redundant sources can still share a weak point, which then becomes a [[common cause failure]]. NIST found that the risers of WTC 1, 2 and 7 provided redundant supply. Each floor's sprinkler system, however, had a single connection to the riser, a single point of failure for the sprinklers on that floor.<ref name="EV-41">Evans et al. (2005), p. 41.</ref> The emergency fire pumps lacked remote redundancy in their power lines, which could have affected the sprinklers and standpipes once power was lost.<ref name="EV-42">Evans et al. (2005), p. 42.</ref>

At one chemical plant, the fire pump house flooded three times in five years, and the pump controllers were shut off each time. The pumps thus formed a common cause failure for numerous deluge systems. Barry gives target availabilities for such systems of 0.98 to 0.999.<ref name="BA-203">Barry (2002), p. 5-203.</ref>

== Limits and practical issues ==
A design water supply covers the expected fire, not every fire. In the World Trade Center, the secondary water supply for the high and mid-level zones depended on manually started fire pumps. NIST notes that an automatic supplemental supply is required by NFPA 14 and represents current best practice.<ref name="EV-41" /> The lower floors of WTC 7 were supplied directly from the city system, so there was no secondary source if that system failed.<ref name="EV-40" /><ref name="EV-41" /> A long run of 4 in. pipe from the 110th floor tanks restricted the flow to several floors, although it was sufficient for the design.<ref name="EV-41" />

New hazards can change the demand. NIPV reports that fires in electric vehicles in car parks need large amounts of water for a long time to cool effectively. The extinguishing water supply and water drainage should be designed for this, and contaminated cooling water needs attention.<ref name="NIPV-6">Van der Graaf et al. (2021/2023), p. 6.</ref> The operating time of a sprinkler system, typically 30 to 120 minutes depending on the standard, limits how long it can support the fire service.<ref name="NIPV-47">Van der Graaf et al. (2021/2023), p. 47.</ref> Firefighting water can also harm the environment. The International Fire Engineering Guidelines name run-off of firefighting water from a chemical warehouse as an example.<ref name="IFEG-2.9-3">National Research Council of Canada et al. (2005), p. 2.9-3.</ref>

Statistics on sprinkler performance can hide supply problems. Australian and New Zealand data in the International Fire Engineering Guidelines show that 65 % of fires were controlled by one sprinkler head. These data exclude fires in which sprinklers failed to operate or water supplies were not available, so they may not reflect the overall reliability of sprinkler systems.<ref name="IFEG-3.7-3">National Research Council of Canada et al. (2005), p. 3.7-3.</ref>

== See also ==
* [[Wet pipe sprinkler system]]
* [[Dry pipe sprinkler system]]
* [[Deluge system]]
* [[Sprinkler design density]]

== Notes ==
<references />

== References ==
* Australian Building Codes Board. (2020a). ''Data sheets: Fire Safety Verification Method'' (Handbook annex, Print version 1.1).
* Australian Building Codes Board. (2022). ''Fire Safety Verification Method Standard 2022''.
* Barry, T. F. (2002). Quantitative risk assessment in chemical process industries. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-176–5-213). National Fire Protection Association; Society of Fire Protection Engineers.
* Evans, D. D., Peacock, R. D., Kuligowski, E. D., Dols, W. S., & Grosshandler, W. L. (2005). ''Active fire protection systems'' (NIST NCSTAR 1-4). National Institute of Standards and Technology.
* Fleming, R. P. (2002). Automatic sprinkler system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-72–4-87). National Fire Protection Association; Society of Fire Protection Engineers.
* Hopkins, M., Schoenrock, J., & Budnick, E. (2005). ''Fire suppression systems'' (NIST NCSTAR 1-4B). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Lew, H. S., Bukowski, R. W., & Carino, N. J. (2005). ''Design, construction, and maintenance of structural and life safety systems'' (NIST NCSTAR 1-1). National Institute of Standards and Technology.
* Ministry of Business, Innovation and Employment. (2025b). ''Verification Method C/VM2: Framework for fire safety design'' (2nd ed.).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Van der Graaf, J., Hessels, T., & Rosmuller, N. (2023). ''Fire safety of indoor car parks accommodating electrically powered vehicles''. Nederlands Instituut Publieke Veiligheid. (Original work published 2021)

[[Category:Fire Suppression]]

← Older revision		Revision as of 23:58, 1 November 2026
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	== Sources of water ==		== Sources of water ==
	Water can come from several kinds of source. In the United States, a wet standpipe system needs a direct connection to an automatic water supply. Examples are a city water distribution system, a tank and pump, an elevated tank or a pressure tank.<ref name="HO-21" /> Sprinkler systems draw on the same kinds of source. ~~The~~ US sprinkler standard NFPA 13 refers to separate standards for the supply components. These are NFPA 14 for standpipes, NFPA 20 for fire pumps, NFPA 22 for water tanks and NFPA 24 for private fire service mains.<ref name="FL-73">Fleming (2002), p. 4-73.</ref>		Water can come from several kinds of source. In the United States, a wet standpipe system needs a direct connection to an automatic water supply. Examples are a city water distribution system, a tank and pump, an elevated tank or a pressure tank.<ref name="HO-21" /> Sprinkler systems draw on the same kinds of source. NFPA 13, the US sprinkler standard of the National Fire Protection Association (NFPA), refers to separate standards for the supply components. These are NFPA 14 for standpipes, NFPA 20 for fire pumps, NFPA 22 for water tanks and NFPA 24 for private fire service mains.<ref name="FL-73">Fleming (2002), p. 4-73.</ref>

	If not enough water is available at a suitable pressure, a stored water supply becomes necessary.<ref name="FL-82" /> The basic choice is between an elevated (gravity) tank, a pressure tank, or a suction tank combined with a pump.<ref name="FL-83" /> Without a pump, the energy for the system must come from the height of a gravity tank or from the air pressure in a pressure tank.<ref name="FL-83" />		If not enough water is available at a suitable pressure, a stored water supply becomes necessary.<ref name="FL-82" /> The basic choice is between an elevated (gravity) tank, a pressure tank, or a suction tank combined with a pump.<ref name="FL-83" /> Without a pump, the energy for the system must come from the height of a gravity tank or from the air pressure in a pressure tank.<ref name="FL-83" />
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	<math display="block">t = \frac{V}{Q} = \frac{56.8\ \mathrm{m^3}}{1.893\ \mathrm{m^3/min}} = 30\ \mathrm{min}</math>		<math display="block">t = \frac{V}{Q} = \frac{56.8\ \mathrm{m^3}}{1.893\ \mathrm{m^3/min}} = 30\ \mathrm{min}</math>

	At the maximum flow of 2.839 m³/min, the same tanks last 20 minutes. NIST gives the same values: a minimum of 30 minutes at 500 gpm, without any supplemental water from the domestic system, and 20 minutes at 750 gpm.<ref name="EV-19" /> Fleming's example for a pressure tank shows the same logic. A 30-minute supply for a demand of 140 gpm (530 L/min) requires at least 4,200 gal (15.9 m³) of water, plus the air needed to keep the pressure up.<ref name="FL-83" />		At the maximum flow of 2.839 m³/min, the same tanks last 20 minutes. The National Institute of Standards and Technology (NIST) gives the same values: a minimum of 30 minutes at 500 gpm, without any supplemental water from the domestic system, and 20 minutes at 750 gpm.<ref name="EV-19" /> Fleming's example for a pressure tank shows the same logic. A 30-minute supply for a demand of 140 gpm (530 L/min) requires at least 4,200 gal (15.9 m³) of water, plus the air needed to keep the pressure up.<ref name="FL-83" />

	Hydraulic calculations by NIST for the light hazard sprinkler systems of the towers gave delivered densities of 0.10 to 0.27 gpm/ft² with up to 16 open sprinklers. The primary water supply could maintain these flows for about 10 to 89 minutes, depending on the location and number of open sprinklers.<ref name="EV-32" /> NIST concluded that the storage tanks gave enough duration for normally expected fires to allow the fire department to respond and supplement the supply.<ref name="EV-40">Evans et al. (2005), p. 40.</ref>		Hydraulic calculations by NIST for the light hazard sprinkler systems of the towers gave delivered densities of 0.10 to 0.27 gpm/ft² with up to 16 open sprinklers. The primary water supply could maintain these flows for about 10 to 89 minutes, depending on the location and number of open sprinklers.<ref name="EV-32" /> NIST concluded that the storage tanks gave enough duration for normally expected fires to allow the fire department to respond and supplement the supply.<ref name="EV-40">Evans et al. (2005), p. 40.</ref>
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	Inside tall buildings, risers bring the water to the floors. Standpipe systems are classed as wet, damp or dry by their water supply. Wet systems are filled with water at all times, while manual [[Dry and wet risers\|dry standpipes]] have only fire department connections and no automatic supply.<ref name="HO-21" /> Removing the need for long hose lays from the fire engine to an upper floor improves the initial attack.<ref name="HO-21" /> For Dutch indoor car parks, NIPV notes that a dry riser can shorten the attack time, because less hose has to be rolled out.<ref name="NIPV-66">Van der Graaf et al. (2021/2023), p. 66.</ref>		Inside tall buildings, risers bring the water to the floors. Standpipe systems are classed as wet, damp or dry by their water supply. Wet systems are filled with water at all times, while manual [[Dry and wet risers\|dry standpipes]] have only fire department connections and no automatic supply.<ref name="HO-21" /> Removing the need for long hose lays from the fire engine to an upper floor improves the initial attack.<ref name="HO-21" /> For Dutch indoor car parks, NIPV notes that a dry riser can shorten the attack time, because less hose has to be rolled out.<ref name="NIPV-66">Van der Graaf et al. (2021/2023), p. 66.</ref>

	Occupants can use the same water. The International Fire Engineering Guidelines mention suppression by building occupants with extinguishers and a [[hose reel]].<ref name="IFEG-1.7-1">National Research Council of Canada et al. (2005), p. 1.7-1.</ref> The New York City building code had no requirement for fire extinguishers, because it required occupant hose reels.<ref name="LE-151">Lew et al. (2005), p. 151.</ref> In WTC 7, hose reels were located in the stair enclosures, with hose cabinets throughout the floors.<ref name="HO-128">Hopkins et al. (2005), p. 128.</ref>		Occupants can use the same water. The International Fire Engineering Guidelines mention suppression by building occupants with extinguishers and a [[hose reel]].<ref name="IFEG-1.7-1">National Research Council of Canada et al. (2005), p. 1.7-1.</ref> The New York City building code had no requirement for fire extinguishers, because it required occupant hose reels.<ref name="LE-151">Lew et al. (2005), p. 151.</ref> In World Trade Center Building 7 (WTC 7), hose reels were located in the stair enclosures, with hose cabinets throughout the floors.<ref name="HO-128">Hopkins et al. (2005), p. 128.</ref>

	== Reliability and redundancy ==		== Reliability and redundancy ==
	Several common causes of sprinkler failure lie in the water supply. The NRC lists a closed water supply valve, a broken supply header, an empty water tank and a fire pump that fails to start among the causes.<ref name="IS-10-2" /> An electric pump can fail through a power failure, and a diesel pump through poor maintenance, dead batteries or lack of fuel.<ref name="IS-10-2" /> The Australian data sheets summarise US statistics by Ahrens. A system that was shut off accounted for 59 % of the cases in which a sprinkler system failed to operate. When systems did operate but were ineffective, 30 % of the cases involved not enough water being discharged.<ref name="AH-79">Ahrens (2017), as cited in Australian Building Codes Board (2020a), Data Sheet C2, p. 79.</ref>		Several common causes of sprinkler failure lie in the water supply. The US Nuclear Regulatory Commission (NRC) lists a closed water supply valve, a broken supply header, an empty water tank and a fire pump that fails to start among the causes.<ref name="IS-10-2" /> An electric pump can fail through a power failure, and a diesel pump through poor maintenance, dead batteries or lack of fuel.<ref name="IS-10-2" /> The Australian data sheets summarise US statistics by Ahrens. A system that was shut off accounted for 59 % of the cases in which a sprinkler system failed to operate. When systems did operate but were ineffective, 30 % of the cases involved not enough water being discharged.<ref name="AH-79">Ahrens (2017), as cited in Australian Building Codes Board (2020a), Data Sheet C2, p. 79.</ref>

	The [[reliability of fire protection systems]] therefore depends strongly on valves and their management. An Australian fault tree study of sprinkler systems in high-rise offices found reliabilities between 86.6 % and 97.9 %. Shutting off sprinkler zones during tenancy changes was one of the main factors in failure.<ref name="MT-81">Moinuddin and Thomas, as cited in Australian Building Codes Board (2020a), Data Sheet C2, p. 81.</ref> According to the fault tree analysis, a zone isolation valve for each floor could reduce the failure probability by 10 % to 63 % of its original value.<ref name="MT-81" />		The [[reliability of fire protection systems]] therefore depends strongly on valves and their management. An Australian fault tree study of sprinkler systems in high-rise offices found reliabilities between 86.6 % and 97.9 %. Shutting off sprinkler zones during tenancy changes was one of the main factors in failure.<ref name="MT-81">Moinuddin and Thomas, as cited in Australian Building Codes Board (2020a), Data Sheet C2, p. 81.</ref> According to the fault tree analysis, a zone isolation valve for each floor could reduce the failure probability by 10 % to 63 % of its original value.<ref name="MT-81" />