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The water supply for sprinkler systems shall be taken from one or more of the following sources:
(a) Gravity tanks. Having a capacity sufficient to supply not less than 25 percent of the total number of heads in the largest fire area served for a period of not less than 20 minutes. The bottom of the tank shall be not less than 35 feet above the highest sprinkler connected thereto and the discharge from each sprinkler shall be calculated as 22 gallons per minute; the minimum capacity of the tank shall be 10,000 gallons.
(b) Pressure tanks. Having a capacity of not less than 4,500 gallons and not more than 9,000 gallons each, designed to be two-thirds full of water and one- third full of air at a pressure of not less than 75 pounds per square inch. Total water capacity of tanks in gallons shall be calculated as given in the gravity tank capacity section. The drop from the gravity tank shall be arranged to enter the line from the pressure tank at a level at least 35 feet below the bottom of the gravity tank and the gravity tank check valve shall be at this level when both gravity tank and pressure tank are used.
(c) Fire pumps, connected to a city water main, having a capacity sufficient to supply not less than 25 percent of sprinklers in the largest fire area except that no fire pump supplying sprinklers only need be larger than 1,500 gallons. Capacity of a fire pump shall be not less than 500 gallons per minute; however, a 250 gallons per minute sprinkler fire pump supplied by not less than a four-inch connection to the city water may be used in a school, an institutional unit, or a building used only as a residential unit which does not exceed four stories or 55 feet in height and which has less than 100 sprinkler heads in any sprinkler area. The discharge from each sprinkler head shall be calculated as 22 gallons per minute. The pressure shall be sufficient to provide 18 pounds per square inch at the highest sprinkler for a system not utilizing hydraulic design.
A fire pump may supply both a sprinkler system and an inside standpipe system; provided, however, the capacity of the pump is equal to the required capacity for the automatic sprinkler system and one-half the required capacity for the standpipe system. It shall be designed to meet the pressure requirements prescribed for the more severe service. The city connection shall be increased two inches if used to supply both domestic service and fire protection demands when the domestic service exceeds two inches.
(d) City mains. City water mains having sufficient volume and residual pressure in the main to supply 25 percent of the total number of sprinklers in the largest fire area to a maximum of 1,500 gallons per minute at a residual pressure of 18 pounds per square inch at the level of the highest sprinkler for a system not utilizing hydraulic design. The discharge shall be calculated as 22 gallons per minute.
(Prior code § 91-11; Amend Coun. J. 10-30-96, p. 31216, § 1)
Gravity tanks shall be constructed and installed in accordance with the requirements of the Chicago Building Code in place at the time such construction or installation occurred. Provided, however, that gravity tanks constructed after September 10, 2014, shall be constructed and installed in accordance with N.F.P.A. Standard 22, Standard for Water Tanks for Private Fire Protection, 2013 Edition, as amended. Provided further, that all gravity tanks, regardless of the date of construction or installation, shall be maintained and disassembled in accordance with the latest edition of N.F.P.A. Standard 22, as amended.
(Prior code § 91-13; Amend Coun. J. 10-30-96, p. 31216, § 1; Amend Coun. J. 7-30-14, p. 86203, § 14)
The materials and construction of tanks under pressure shall be in accordance with the American Society of Mechanical Engineers “Rules for the Construction of Unfired Pressure Vessels”, Section VIII, dated 1986.
They shall be installed on steel or reinforced concrete supports, located so as to prevent sagging or vibration in the tanks and so as to distribute the load. Each tank shall be provided with a glass water column installed on one end of the tank at such a height that the center of the gauge glass shall be at the normal level of the water in the tank and equipped with automatic safety cocks.
(Prior code § 91-14; Amend Coun. J. 10-30-96, p. 31216, § 1)
Fire pumps and auxiliary equipment, including controllers required to form complete pumping units, shall be of a type designed and developed for sprinkler service. The installation shall comply with NFPA 20-2013. The suction pipe shall be six inches for 500 and 750 gallons per minute pumps and eight inches for 1,000 and 1,500 gallons per minute pumps. The city connection shall be increased two inches if used for both domestic consumption and fire protection demands when the domestic service exceeds two inches.
In each case the pump used shall be selected to meet the conditions surrounding the installation. The pumping unit shall be designed to develop full capacity at its rated pressure. The design and installation of a pump shall be such that under any flow rate the intake pressure at the pump shall be not less than five pounds per square inch.
A fire pump shall be automatic in operation. A time delay device set for one minute for each ten horsepower of motor rating but not to exceed seven minutes shall be provided. A separate automatically controlled centrifugal pressure maintenance pump to avoid too frequent starting and stopping of the fire pump shall be provided.
(Prior code § 91-15; Amend Coun. J. 10-30-96, p. 31216, § 1; Amend Coun. J. 9-6-17, p. 55278, Art. VII, § 23)
Each fire pump which supplies an automatic sprinkler system shall be provided with a discharge test manifold having one two and one-half inch corrosion resistant valve for each 250 gallons per minute of rated pumping capacity; however, no more than six valves need be provided. The discharge test manifold shall be located on an outside wall in a location which will permit safe discharge and drainage of water.
(Added Coun. J. 10-30-96, p. 31216, § 1)
A gravity tank used for a sprinkler system shall be supplied with water by a filling pump having a capacity such that the tank can be filled in less than eight hours.
The pressure tanks shall be supplied with water by a filling pump having a capacity such that the tank can be filled in not mom than four hours and with air by an air compressor having a capacity of not less than 20 cubic feet of free air per minute if of 7,500 gallon capacity or over and 16 cubic feet of free air per minim if under 7,500 gallon capacity. Where the sprinkler system is equipped with both gravity and pressure tanks, one filling pump may be provided for both. Any storage tank used for fire protection purposes when supplied from the city water system shall conform to the piping provisions governing fill lines and overflow pipes for storage tanks prescribed in Chapter 11-8 of this code.
(Prior code § 91-16; Amend Coun. J. 10-30-96, p. 31216, § 1)
The filling pipe to the gravity tank of any system shall be not less than two inches in diameter.
The water filling pipe to the pressure tanks shall be not less than one and one-half inches in diameter; it shall be run separately from the source of supply with a bronze seat check valve and a renewable disc angle valve provided in the pipe near the tank, the angle valve being placed between the check valve and the tank. The air supply pipe shall be not less than one inch in diameter and shall have a bronze seat check valve and renewable disc angle check valve provided in the pipe near the tank with the angle valve between the tank and check valve. The air supply pipe shall be connected to the tanks above the water level in the tanks.
(Prior code § 91-17; Amend Coun. J. 10-30-96, p. 31216, § 1)
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