# 77 Ill. Adm. Code 890.1170: Section 890.1170 Potable Water Supply Tanks and Auxiliary Pressure Tanks > Illinois · Regulations · In force URL: https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1170 ## Section - **Citation:** 77 Ill. Adm. Code 890.1170 - **Heading:** Section 890.1170 Potable Water Supply Tanks and Auxiliary Pressure Tanks - **Jurisdiction:** Illinois - **Kind:** Regulations - **Status:** In force - **Text as of:** August 14, 2026 - **Source:** Compiled text - **Location:** Illinois Administrative Code / Title 77 PUBLIC HEALTH / CHAPTER I: DEPARTMENT OF PUBLIC HEALTH / Part 890 ILLINOIS PLUMBING CODE / Section 890.1170 Potable Water Supply Tanks and Auxiliary Pressure Tanks ## Text Section 890 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 nd 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).) ## Nearby sections - [77 Ill. Adm. Code 890.1110 Section 890.1110 Quality of Water Supply](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1110.md) - [77 Ill. Adm. Code 890.1120 Section 890.1120 Color Code](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1120.md) - [77 Ill. Adm. Code 890.1130 Section 890.1130 Protection of Potable Water](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1130.md) - [77 Ill. Adm. Code 890.1140 Section 890.1140 Special Applications and Installations](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1140.md) - [77 Ill. Adm. Code 890.1150 Section 890.1150 Water Service Pipe Installation](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1150.md) - [77 Ill. Adm. Code 890.1160 Section 890.1160 Potable Water Pumping and Storage Equipment](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1160.md) - [77 Ill. Adm. Code 890.1170 Section 890.1170 Potable Water Supply Tanks and Auxiliary Pressure Tanks](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1170.md) - [77 Ill. Adm. Code 890.1180 Section 890.1180 Flushing/Disinfection of Potable Water System](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1180.md) - [77 Ill. Adm. Code 890.1190 Section 890.1190 Water Supply Control Valves and Meter](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1190.md) - [77 Ill. Adm. Code 890.1200 Section 890.1200 Water Service Sizing](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1200.md) - [77 Ill. Adm. Code 890.1210 Section 890.1210 Design of a Building Water Distribution System](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1210.md) - [77 Ill. Adm. Code 890.1220 Section 890.1220 Hot Water Supply and Distribution](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1220.md) - [77 Ill. Adm. Code 890.1230 Section 890.1230 Safety Devices](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1230.md) - [77 Ill. Adm. Code 890.1240 Section 890.1240 Miscellaneous](https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1240.md) --- Source: Frix Law Library, https://www.frixlaw.com/law-library/statutes/STATE_IL_IAC_T77_P890_S890_1170. Check the current official text before relying on it. Not legal advice.