Section 890.1170  Potable Water Supply Tanks and Auxiliary Pressure Tanks

a)         Water Pressure.  When the water pressure from the public water supply main is insufficient during periods of peak flow or due to the building height to supply all fixtures in accordance with Section 890.1210(c), the rate of supply shall be supplemented by a gravity tank or auxiliary pressure (booster) system.  Auxiliary pressure systems shall not substitute for adequate sizing of water distribution piping within the building.

b)         Support.  All water supply tanks shall be supported in accordance with local building codes or authorities having jurisdiction.

c)         Tank Supply Inlet and Outlet.  The water supply inlet to the tank shall have a minimum air gap of at least 6 inches.  The supply outlet shall be a minimum of 4 inches above the bottom of the tank.

d)         Overflow For Water Supply Tanks.  Overflow pipes for gravity tanks shall be indirectly connected to the drainage system with an air gap of at least 6 inches.  Overflow pipes shall be full sized, unrestricted and screened with 24-mesh per inch stainless steel or bronze screen.

e)         Size of Overflow.  Overflow drains for gravity water supply tanks shall have an area of at least twice the size of the supply pipe.

f)         Drains.  Water supply tanks shall be provided with valved drain lines located at their lowest point and shall discharge through an indirect waste with an air gap of twice the diameter of the drain line.  The drain line and valve shall have no restrictions and need not exceed 2 inches in diameter.

g)         Gravity and Suction Tanks.  Tanks used for potable water supply or only to supply fire-fighting equipment shall be equipped with tight, overlapping covers that are rodent and insect proof.  The tanks shall be vented with a return bend (turned down) pipe having an area at least ½ the area of the tank outlet pipe, and the vent opening shall be covered with a stainless steel or bronze screen of at least 24-mesh per inch.

h)         Pressure Tanks.  Pressure tanks used for supplying water to the water distribution system, or only to supply standpipes for fire equipment, shall be equipped with a vacuum relief valve located on top of the tank.  An air inlet of this device shall be covered with a stainless steel or bronze screen of at least 24-mesh per inch.  (See Section 890.1230(f).)

(Source:  Amended at 38 Ill. Reg. 9940, effective April 24, 2014)