SECTION 4.3 – TANK STORAGE
Section 4.3 Tank Storage
Subsection 4.3.1. Design, Construction and Use of Storage Tanks
Application
4.3.1.1. This Section applies to storage tanks for flammable liquids and combustible liquids.
Atmospheric storage tanks
4.3.1.2. (1) Except as permitted in Sentences (3) and (5) and in Section 4.10., atmospheric storage tanks shall be built in conformance with the following:
(a) except as provided in Sentence (2), API SPEC 12B, “Specification for Bolted Tanks for Storage of Production Liquids”,
(b) except as provided in Sentence (2), API SPEC 12D, “Specification for Field Welded Tanks for Storage of Production Liquids”,
(c) except as provided in Sentence (2), API SPEC 12F, “Specification for Shop Welded Tanks for Storage of Production Liquids”,
(d) API STD 650, “Welded Tanks for Oil Storage”,
(e) CAN/ULC-S601, “Standard for Shop Fabricated Steel Aboveground Tanks for Flammable and Combustible Liquids”,
(f) CAN/ULC-S602, “Standard for Steel Aboveground Tanks for Fuel Oil and Lubricating Oil”,
(g) CAN/ULC-S603, “Standard for Steel Underground Tanks for Flammable and Combustible Liquids”,
(h) CAN/ULC-S603.1, “Standard for External Corrosion Protection Systems for Steel Underground Tanks for Flammable and Combustible Liquids”,
(i) CAN/ULC-S615, “Standard for Fibre Reinforced Plastic Underground Tanks for Flammable and Combustible Liquids”,
(j) CAN/ULC-S652, “Standard for Tank Assemblies for the Collection, Storage and Removal of Used Oil”,
(k) CAN/ULC-S653, “Aboveground Steel Contained Tank Assemblies for Flammable and Combustible Liquids”,
(l) ULC-S655, “Aboveground Protected Tank Assemblies for Flammable and Combustible Liquids”,
(m) CAN/ULC-S677, “Standard for Fire Tested Aboveground Tank Assemblies for Flammable and Combustible Liquids”, or
(n) ANSI/CAN/UL/ULC 2258, “Standard for Aboveground Nonmetallic Tanks for Fuel Oil and Other Combustible Liquids”.
(2) Tanks built in conformance with Clause (1)(a), (b) or (c) shall be
(a) used only for the storage of crude petroleum and oil field production liquids, and
(b) provided with emergency venting that
(i) conforms to API STD 2000, “Venting Atmospheric and Low-Pressure Storage Tanks”, and
(ii) is compatible with the design features of the tank.
(3) When necessitated by possible contamination of the liquid to be stored or possible rapid corrosion of the tank, storage tanks need not conform to Sentence (1), provided that they are designed and built in conformance with good engineering practice for the material being used.
(4) Atmospheric storage tanks shall not be used for the storage of flammable liquids or combustible liquids at temperatures at or above their boiling points.
(5) Atmospheric storage tanks that are installed and currently in use, that met the requirements of this Code on December 31, 2025, as it read at the time, and that continue to meet those requirements are deemed to comply with Sentence (1).
Low pressure storage tanks and pressure vessels
4.3.1.3. (1) Low pressure storage tanks shall be constructed in conformance with
(a) API STD 620, “Design and Construction of Large, Welded, Low-Pressure Storage Tanks”, or
(b) ASME BPVC, “Boiler and Pressure Vessel Code”.
(2) Pressure vessels shall be constructed in conformance with CSA B51, “Boiler, Pressure Vessel and Pressure Piping Code”.
(3) Low pressure storage tanks and pressure vessels are permitted to be used as atmospheric storage tanks.
Operating pressure
4.3.1.4. The normal operating pressure of a storage tank shall not exceed its design pressure.
Corrosion protection
4.3.1.5. Aboveground storage tanks and their integral fittings that are subject to corrosion shall be protected by any means against exposure to conditions that would initiate corrosion.
Floating roofs
4.3.1.6. Except for perimeter sealing material, floating roof assemblies or internal floating covers installed in storage tanks shall be constructed of metal or other materials and designed in conformance with one of the tank construction standards listed in this Subsection.
Identification
4.3.1.7. (1) A storage tank and its filling and emptying connections shall be identified in conformance with CFA 1990, “Using the Canadian Fuels Colour-Symbol System to Mark Equipment and Vehicles for Product Identification”.
(2) A storage tank and its filling and emptying connections that were identified in conformance with the requirements of this Code on or before December 31, 2025, as it read at the time, and that continue to meet those requirements are deemed to comply with Sentence (1).
Overfill protection
4.3.1.8. (1) Except as required in Sentences (2) and (3), a storage tank shall be prevented from being overfilled by providing
(a) continuous supervision of the filling operations by persons qualified to supervise such operations, or
(b) an overfill protection device conforming to CAN/ULC-S661, “Standard for Overfill Protection Devices for Flammable and Combustible Liquid Storage Tanks”.
(2) Except as provided in Sentence (3), tight-filled aboveground horizontal storage tanks and underground storage tanks shall be prevented from being overfilled by providing a positive shut-off device conforming to CAN/ULC-S661, “Standard for Overfill Protection Devices for Flammable and Combustible Liquid Storage Tanks”.
(3) Storage tanks that are filled remotely with used lubricating oil described in Article 4.1.2.4. shall be prevented from being overfilled by providing an overfill protection device in accordance with Clause (1)(b).
(4) Storage tanks that are installed and currently in use, that met the requirements of this Code on December 31, 2025, as it read at the time, and that continue to meet those requirements are deemed to comply with Sentences (1), (2) and (3).
Installation and use
4.3.1.9. Unless otherwise specified in this Code, a storage tank shall be installed and used in conformance with the applicable installation and use provisions of the design document to which the storage tank was built as required by this Section.
Reuse
4.3.1.10. (1) A storage tank that has been taken out of service shall not be reused for the storage of flammable liquids or combustible liquids unless it has been
(a) refurbished so as to conform to one of the standards listed in Sentence 4.3.1.2.(1),
(b) refurbished so as to conform to CAN/ULC-S676, “Standard for Refurbishing of Storage Tanks for Flammable and Combustible Liquids”, or
(c) refurbished in conformance with Sentence (2) or (3).
(2) A storage tank is permitted to be refurbished for aboveground use in conformance with
(a) API STD 653, “Tank Inspection, Repair, Alteration, and Reconstruction”, and
(b) STI/SPFA SP031, “Standard for Repair of Shop Fabricated Aboveground Tanks for Storage of Flammable and Combustible Liquids”.
(3) A storage tank is permitted to be refurbished for underground use in conformance with CAN/ULC-S669, “Standard for Internal Retrofit Systems for Underground Tanks for Flammable and Combustible Liquids”.
(4) A riveted storage tank shall not be relocated.
(5) A refurbished storage tank that is installed and currently in use, that met the requirements of this Code on December 31, 2025, as it read at the time, that was refurbished on or before that day and that continues to meet those requirements is deemed to comply with Sentence (1).
Subsection 4.3.2. Installation of Outside Aboveground Storage Tanks
Location
4.3.2.1. (1) Every outside aboveground storage tank for the storage of flammable liquids or combustible liquids shall be located in conformance with Sentences (2) to (5) with respect to a property line or a building on the same property.
(2) Except as provided in Sentences (6) and (7), every aboveground storage tank containing stable liquids and having a working pressure of not more than 17 kPa (gauge) shall be separated from a property line or a building on the same property by distances
(a) half those in Table 4.3.2.1., where protection is provided against fire or explosion in the tank in conformance with Sentence 4.3.2.5.(2), or
(b) equal to those in Table 4.3.2.1., where protection referred to in Clause (a) is not provided.
(3) Every aboveground storage tank containing unstable liquids and having a working pressure of not more than 17 kPa (gauge) shall be separated from a property line or a building on the same property by distances
(a) equal to those in Table 4.3.2.1., but not less than 7.5 m, where protection is provided against fire or explosion in the tank in conformance with Sentence 4.3.2.5.(2), or
(b) three times those in Table 4.3.2.1., but not less than 15 m, where protection referred to in Clause (a) is not provided.
(4) Every aboveground storage tank containing boil-over liquids shall be separated from a property line or a building on the same property by distances
(a) 0.75 times those in Table 4.3.2.1., where protection is provided against fire or explosion in the tank in conformance with Sentence 4.3.2.5.(2), or
(b) equal to those in Table 4.3.2.1., where protection referred to in Clause (a) is not provided.
(5) Where a storage tank containing stable liquids or unstable liquids has a working pressure greater than 17 kPa (gauge), the distances from a property line or a building on the same property shall be those specified in Sentences (2) and (3) multiplied by 1.5, but shall be not less than 7.5 m.
(6) The minimum distance required in Sentence (2) from a storage tank containing only Class II or IIIA liquids to a building on the same property is permitted to be reduced to
(a) 1.5 m provided the tank capacity is not more than 50000 L, or
(b) zero provided the tank capacity is not more than 2500 L.
(7) The minimum distance required in Sentence (2) is permitted to be waived provided the storage tank is in conformance with ULC-S655, “Aboveground Protected Tank Assemblies for Flammable and Combustible Liquids” and has a capacity of not more than 50000 L.
(8) Where end failure of horizontal storage tanks may endanger adjacent property, the tanks shall be placed with the longitudinal axis parallel to such property.
Table 4.3.2.1.
Location of Aboveground Storage Tanks Forming Part of Article 4.3.2.1.
| Maximum Tank Capacity, L | Minimum Distance to a Property Line or to a Building on the Same Property, m |
| 250000 | 3 |
| 500000 | 4.5 |
| 2500000 | 9 |
| 5000000 | 12 |
| > 5000000 | 15 |
Spacing between storage tanks
4.3.2.2. (1) Except as required in Sentences (2) and (3) and in Article 4.3.2.3., the minimum distance between every combination of two aboveground storage tanks shall be 0.25 times the sum of their diameters, but shall be not less than 1 m.
(2) The minimum distance between any two storage tanks, neither of which has a capacity of more than 250000 L, shall be 1 m.
(3) Where either of two aboveground storage tanks contains unstable liquids, the distance required in Sentences (1) and (2) shall be doubled.
Clearances from liquefied petroleum gas cylinders and tanks
4.3.2.3. (1) The minimum separation between a flammable liquid or combustible liquid storage tank and a liquefied petroleum gas cylinder or tank shall be 6 m.
(2) Secondary containments for flammable liquid and combustible liquid storage tanks shall not contain any liquefied petroleum gas cylinder or tank, and the centre line of the secondary containment wall shall be not less than
(a) 3 m away from a liquefied petroleum gas cylinder, and
(b) 6 m away from a liquefied petroleum gas tank.
Fire department access
4.3.2.4. (1) Except as provided in Sentences (2) and (3), storage tanks for flammable liquids or combustible liquids shall be spaced so that each storage tank is accessible for firefighting purposes.
(2) An access route constructed in conformance with Subsection 3.2.5. of Division B of the Building Code shall be provided in outdoor storage areas to permit the approach of fire department vehicles to within 60 m travelling distance of any storage tank.
(3) Where firefighting access to storage tanks containing Class I or II liquids is not provided, fire extinguishing measures conforming to Sentence 4.3.2.5.(2) shall be provided.
Fire protection systems
4.3.2.5. (1) Where the diameter of a storage tank exceeds 45 m, the storage tank shall be provided with protection against fires or explosions in conformance with Sentence (2).
(2) Protection against fires or explosions required for a storage tank shall consist of fixed protection systems designed in conformance with good engineering practice such as that described in
(a) NFPA 11, “Standard for Low-, Medium-, and High-Expansion Foam”,
(b) NFPA 15, “Standard for Water Spray Fixed Systems for Fire Protection”, and
(c) NFPA 69, “Standard on Explosion Prevention Systems”.
Subsection 4.3.3. Supports, Foundations and Anchorage for Aboveground Storage Tanks
Foundations and supports
4.3.3.1. (1) Storage tanks shall rest on the ground or on foundations, supports or piling made of concrete, masonry or steel.
(2) Tank supports shall be installed on firm foundations designed to minimize uneven settling of the tank and to minimize corrosion of the part of the tank resting on the foundation.
(3) Where the clearance below the base of the tank exceeds 300 mm, tank supports shall have a minimum fire-resistance rating of 2 h.
(4) Every aboveground storage tank shall be supported in a manner that will prevent the allowable design stress of the tank from being exceeded.
Earthquake protection
4.3.3.2. (1) In areas subject to earthquake forces, storage tanks, supports and connections shall be designed to resist such forces in conformance with
(a) Part 4 of Division B of the Building Code, and
(b) Appendix A2 of CAN/ULC-S601, “Shop Fabricated Steel Aboveground Tanks for Flammable and Combustible Liquids”.
Protection against flooding
4.3.3.3. When aboveground storage tanks are located in an area that is subject to flooding, the tanks shall be securely anchored to prevent floating.
Subsection 4.3.4. Normal and Emergency Venting for Aboveground Storage Tanks
Design and installation
4.3.4.1. (1) Atmospheric and low pressure storage tanks shall be provided with normal and emergency venting in conformance with
(a) API STD 2000, “Venting Atmospheric and Low-Pressure Storage Tanks”, or
(b) the tank design standards listed in Sentence 4.3.1.2.(1).
Unstable liquids
4.3.4.2. When unstable liquids are stored, the effects of heat or gas resulting from polymerization, decomposition, condensation or self-reactivity shall be allowed for in the determination of the total venting capacity.
Subsection 4.3.5. Vent Piping for Aboveground Storage Tanks
Materials and construction
4.3.5.1. Except at distilleries covered in Section 4.10., vent piping materials and construction shall conform to Subsections 4.5.2., 4.5.3. and 4.5.5.
Location of vent pipe outlets
4.3.5.2. (1) Normal vent pipe outlets for storage tanks of Class I liquids
(a) shall be located outside buildings not less than
(i) 3.5 m above the adjacent ground level, and
(ii) 1.5 m from any building opening, and
(b) shall discharge so that flammable vapours will not enter the building or be trapped near any part of the building.
(2) Normal vent pipe outlets for storage tanks of Class II or IIIA liquids shall discharge outside buildings not less than
(a) 2 m above the adjacent ground level, and
(b) 1.5 m from any building opening.
(3) Emergency vent outlets for storage tanks shall discharge outside buildings not less than 1.5 m from any building opening and from any combustible component of any building’s exterior wall.
Interconnection of vent piping
4.3.5.3. (1) Except as provided in Sentence (2), two or more storage tanks are permitted to be connected to a common vent pipe for normal relief venting provided the vent pipe size is designed to vent the combined vapours produced in the connected tanks without exceeding the allowable stresses of the tanks.
(2) Vent piping for storage tanks for Class I liquids shall not be connected to vent piping for storage tanks for Class II or IIIA liquids unless an effective arrangement is provided to prevent the vapours from the Class I liquids from entering the other tanks.
Subsection 4.3.6. Openings Other than Vents in Aboveground Storage Tanks
Provision of valves
4.3.6.1. (1) Each connection to an aboveground storage tank through which the liquid can normally flow shall be provided with an internal or external shut-off valve located as close as practical to the shell of the tank.
(2) Each connection to an aboveground storage tank that is below the liquid level and through which liquid does not normally flow shall be provided with a liquid-tight closing device.
Materials
4.3.6.2. (1) Valves and their connections to a storage tank shall be made of steel, except that when the chemical characteristics of the liquid stored are incompatible with steel, materials other than steel are permitted to be used.
(2) Materials for valves and their connections to a storage tank shall be suitable for the pressures, stresses and temperatures that may be expected, including those of possible fire exposure.
Openings for liquid level measurements
4.3.6.3. Openings for measuring liquid levels in storage tanks for Class I liquids shall be equipped with caps or covers which shall be opened only when measuring the liquid level.
Connections for filling and emptying
4.3.6.4. (1) Except as provided in Sentence (3), connections used as part of normal operating conditions for filling or emptying storage tanks for flammable liquids and combustible liquids shall be located
(a) outside buildings,
(b) at a location free of sources of ignition, and
(c) not less than 1.5 m away from building openings.
(2) Connections for filling or emptying storage tanks shall be kept closed to prevent leakage when not in use.
(3) A filling connection described in Sentence (1) is permitted to be located inside a building if
(a) this is made necessary
(i) by a process or activity located indoors and to which the tank is directly associated, or
(ii) for the collection of used liquids, and
(b) the fill piping is provided with means to prevent flammable vapours from returning to the building.
(4) Connections for filling or emptying storage tanks shall be provided with a spill containment device designed to catch, retain and provide for the evacuation of spilled flammable liquids or combustible liquids in conformance with CAN/ULC-S663, “Standard for Spill Containment Devices for Flammable and Combustible Liquid Aboveground Storage Tanks”.
Subsection 4.3.7. Secondary Containment for Aboveground Storage Tanks
General
4.3.7.1. (1) The area surrounding a storage tank or group of storage tanks shall be designed to accommodate accidental spillage in conformance with Subsection 4.1.6.
(2) Where barriers described in Sentence 4.1.6.1.(1) are provided to contain accidental spillage from aboveground storage tanks, they shall conform to the requirements for secondary containment in this Subsection.
(3) A storage tank conforming to Sentence 4.3.7.4.(2) shall be considered as conforming to this Subsection provided it is used and maintained in conformance with Articles 4.3.7.8. and 4.3.7.9.
Construction
4.3.7.2. (1) The base and walls of a secondary containment shall be made of noncombustible materials, and shall be designed, constructed and maintained to
(a) withstand full hydrostatic head, and
(b) provide a permeability of not more than 10-6 cm/s to the flammable liquids or combustible liquids contained in the storage tanks.
(2) A membrane providing the level of impermeability required in Clause (1)(b) shall
(a) conform to CAN/ULC-S668, “Standard for Liners Used for Secondary Containment of Aboveground Flammable and Combustible Liquid Tanks”, and
(b) be installed in accordance with the manufacturer’s instructions.
(3) A membrane that is installed and currently in use, that met the requirements of this Code on December 31, 2025, as it read at the time, and that continues to meet those requirements is deemed to comply with Clause (2)(a).
(4) Except as provided in Sentence (5), openings shall not be permitted in a secondary containment.
(5) Where piping passes through a secondary containment, such passages shall conform to Sentences (1) and (2).
Capacity
4.3.7.3. (1) Except as permitted in Sentence (3), a secondary containment for a single storage tank shall have a volumetric capacity of not less than 110% of the capacity of the tank.
(2) Except as permitted in Sentence (3), a secondary containment for more than one storage tank shall have a volumetric capacity of not less than the sum of
(a) the capacity of the largest storage tank located in the contained space, and
(b) 10% of the greater of
(i) the capacity specified in Clause (a), or
(ii) the aggregate capacity of all other storage tanks located in the contained space.
(3) When the secondary containment is designed to prevent the entry of precipitation and water used for firefighting purposes into the contained space, it shall have a volumetric capacity of not less than the capacity of the largest storage tank located in the contained space.
Clearances
4.3.7.4. (1) Except as provided in Sentence (2), no part of a secondary containment wall shall be less than 1.5 m from a storage tank shell.
(2) The distance required in Sentence (1) is permitted to be waived, provided the storage tank
(a) has a capacity of not more than 50000 L and is constructed in accordance with
(i) CAN/ULC-S652, “Standard for Tank Assemblies for the Collection, Storage and Removal of Used Oil”, CAN/ULC-S653, “Aboveground Steel Contained Tank Assemblies for Flammable and Combustible Liquids”, or CAN/ULC-S677, “Standard for Fire Tested Aboveground Tank Assemblies for Flammable and Combustible Liquids”, incorporating secondary containment, or
(ii) CAN/ULC-S601, “Shop Fabricated Steel Aboveground Tanks for Flammable and Combustible Liquids”, for double-walled storage tanks, or
(b) conforms to ULC-S655, “Aboveground Protected Tank Assemblies for Flammable and Combustible Liquids”.
(3) Aboveground storage tanks shall be protected by posts or guardrails where they are exposed to potential collision damage.
(4) Secondary containment walls that are installed and currently in use, that met the requirements of this Code on December 31, 2025, as it read at the time, and that continue to meet those requirements are deemed to comply with Sentences (1), (2) and (3).
Access to storage tanks and ancillary equipment
4.3.7.5. (1) A secondary containment shall permit
(a) access to storage tanks, valves and ancillary equipment,
(b) egress from the contained space, and
(c) access for firefighting as specified in Article 4.3.2.4.
(2) Where a storage tank contains Class I liquids, provisions shall be made for the normal operation of valves and for access to the storage tank roof without entering the contained space created by the secondary containment when
(a) the average height of the secondary containment exceeds 3.5 m, measured from the ground level of the interior of the contained area, or
(b) the distance between the tank shell and the top inside edge of the secondary containment wall is less than the height of this wall.
Emergency venting
4.3.7.6. Where the secondary containment is not open to the atmosphere, emergency venting shall be provided to relieve any buildup of internal pressure in the contained space when exposed to heat or fire.
Leak detection
4.3.7.7. Where the contained space created by the secondary containment is not accessible for an internal visual examination and the secondary containment is not sloped so as to permit liquid to flow to a specific location that can be monitored, a monitoring device shall be provided to indicate the loss of integrity of the secondary containment.
Drainage
4.3.7.8. (1) Liquids, debris and precipitation shall not accumulate in the contained space created by the secondary containment.
(2) Provisions shall be made for removing liquid from the secondary containment in conformance with Subsection 4.1.6.
(3) Controls for the liquid removal system required in Sentence (2) shall be
(a) normally closed,
(b) accessible under fire exposure conditions, and
(c) located so they can be operated from outside the contained space.
Use of secondary containment
4.3.7.9. The contained space created by a secondary containment shall not be used for storage purposes.
Subsection 4.3.8. Installation of Underground Storage Tanks
Construction
4.3.8.1. (1) Storage tanks installed underground shall be of double-walled construction and shall be built in conformance with the underground storage tank standards identified in Sentence 4.3.1.2.(1).
(2) Underground storage tanks that are installed and currently in use, that met the requirements of this Code on December 31, 2025, as it read at the time, and that do not comply with Sentence (1) may remain in-service if the tanks continue to meet those requirements and are not leaking.
Location
4.3.8.2. (1) Underground storage tanks shall be located so that loads from building foundations and supports are not transmitted to the tank and the foundations of buildings will not be undermined during excavation.
(2) Underground storage tanks shall be separated by a horizontal distance of not less than
(a) 600 mm from adjacent underground tanks or structures,
(b) 1 m from a building foundation or a street line, and
(c) 1.5 m from other property lines.
Ground cover
4.3.8.3. (1) Except as required in Sentences (2) to (4), underground storage tanks shall be installed with not less than 600 mm of ground cover over the tank.
(2) Except as required in Sentence (3), storage tanks subjected to vehicular traffic shall be installed not less than 1 m below finished ground level.
(3) Either a 150 mm reinforced concrete slab or a 200 mm unreinforced concrete slab over not less than 450 mm of sand is permitted in lieu of the protection described in Sentence (2) provided the slab extends at least 300 mm beyond the storage tank.
(4) Where subsurface conditions make it impracticable to install a storage tank totally below adjacent ground level, an underground storage tank shall be installed so that at least
(a) 75% of its mass is below adjacent ground level, provided there is not less than 600 mm of ground cover over the portion of the tank above adjacent ground level, or
(b) 50% of its mass is below adjacent ground level, provided there is not less than 1 m of ground cover over the portion of the tank above adjacent ground level.
Damage repair
4.3.8.4. (1) Underground storage tanks that are in the process of being installed shall be inspected and any damage to the tank shell, protective coating, fittings or anodes shall be repaired before they are lowered into the excavation.
(2) Damage to storage tank shells shall not be repaired on site.
Damage prevention
4.3.8.5. (1) Underground storage tanks shall be lowered into the excavation by the use of lifting lugs and hooks and, where necessary, spreader bars to prevent damage to the tank shell, protective coating, fittings or anodes.
(2) Any method of handling that might result in damage to the protective coating of the tank shall not be used.
Installation
4.3.8.6. (1) Underground steel storage tanks shall be installed in conformance with Appendix A of CAN/ULC-S603.1, “Standard for External Corrosion Protection Systems for Steel Underground Tanks for Flammable and Combustible Liquids”.
(2) Underground reinforced plastic storage tanks shall be installed in conformance with Appendix B of CAN/ULC-S615, “Standard for Fibre Reinforced Plastic Underground Tanks for Flammable and Combustible Liquids”.
(3) Underground storage tanks shall not be placed in direct contact with concrete slabs but shall be separated by not less than 150 mm of sand or other suitable reinforced material to evenly distribute the weight of the tank on the supporting base.
Filling
4.3.8.7. (1) Flammable liquids or combustible liquids shall not be placed in an underground storage tank until
(a) the fill pipe and vent line have been installed in the tank, and
(b) all other openings have been sealed.
Spillage
4.3.8.8. If a spillage occurs, the escaped liquid and all soil contaminated by the spill shall be removed in conformance with Subsection 4.1.6.
Anchorage
4.3.8.9. (1) Underground storage tanks shall be protected against hydrostatic forces which can cause the uplift of the tanks once they are empty.
(2) Where anchors and ground straps are used to resist the uplift forces referred to in Sentence (1), they shall be
(a) electrically isolated from the tank, and
(b) installed in such a manner that they do not damage the tank’s shell, protective coating, fittings or anodes.
Subsection 4.3.9. Sumps
Installation
4.3.9.1. (1) A dispenser sump shall be provided under a dispenser, unless the dispenser is located on top of an aboveground storage tank.
(2) A spill containment sump shall be provided at every underground storage tank fill point.
(3) A transition sump shall be provided for all mechanical pipe connections located below grade.
(4) A turbine sump shall be provided for all turbine pump assemblies located below grade or above grade where they are not readily visible.
(5) In addition to the requirements of Article 4.3.9.2., the sumps referred to in Sentences (1) to (4) shall be installed in conformance with the sump manufacturer’s instructions.
Construction
4.3.9.2. Sumps required by Article 4.3.9.1. shall be constructed in accordance with CAN/ULC-S664, “Standard for Containment Sumps, Sump Fittings, and Accessories for Flammable and Combustible Liquids”.
Leak detection monitoring
4.3.9.3. Where dispenser sumps, turbine sumps and transition sumps referred to in Article 4.3.9.1. are used in underground applications, they shall be provided with an electronic monitoring device to indicate the presence of liquid.
Subsection 4.3.10. Corrosion Protection of Underground Steel Storage Tanks
Corrosion protection
4.3.10.1. (1) Underground steel storage tanks and integral fittings subject to corrosion shall be
(a) protected in conformance with CAN/ULC-S603.1, “Standard for External Corrosion Protection Systems for Steel Underground Tanks for Flammable and Combustible Liquids”, or
(b) protected by impressed current in conformance with NACE SP0285, “Corrosion Control of Underground Storage Tank Systems by Cathodic Protection”.
Subsection 4.3.11. Vents for Underground Storage Tanks
Vent design
4.3.11.1. Underground storage tanks shall be provided with vent openings and piping of sufficient cross-sectional area designed to vent the tanks during the maximum filling or withdrawal rate without causing the allowable stress for the tank to be exceeded.
Materials and construction
4.3.11.2. Except at distilleries covered in Section 4.10, vent piping materials and construction shall conform to Subsections 4.5.2., 4.5.3. and 4.5.5.
Installation
4.3.11.3. (1) Vent pipe outlets from underground storage tanks for Class I liquids
(a) shall be located outside buildings higher than the fill pipe openings but not less than
(i) 3.5 m above the adjacent ground level,
(ii) 1.5 m from any building opening, and
(iii) 7.5 m from any dispenser, and
(b) shall discharge so that flammable vapours will not enter building openings or be trapped near any part of the building.
(2) Vent pipe outlets from underground storage tanks for Class II or IIIA liquids shall be located outside buildings at a height that is above the fill pipe opening but not less than 2 m above finished ground level.
(3) Vent pipes from underground storage tanks for flammable liquids or combustible liquids shall not be obstructed by any device that may cause excessive back pressure, except that vent pipes from underground storage tanks for Class II or IIIA liquids are permitted to be fitted with return bends, coarse screens or other devices to minimize the entry of foreign material.
(4) Vent piping shall enter the storage tank through the top of the tank and shall not extend into the tank more than 25 mm.
(5) Vent piping shall be
(a) installed so that any nominally horizontal run shall slope towards the storage tank,
(b) constructed without traps,
(c) adequately supported to prevent sagging, and
(d) where necessary, protected against mechanical damage.
(6) Vent piping shall be tested for leaks at the commissioning stage in conformance with Clause 4.4.1.2.(1)(a).
(7) Vent piping with operational vent alarms that are installed and currently in use, that met the requirements of this Code on December 31, 2025, as it read at the time, and that continue to meet those requirements are deemed to comply with Sentence (4).
Interconnection of vent pipes
4.3.11.4. (1) Except as permitted in Sentence (2), where vent piping connects two or more storage tanks, pipe sizes shall be designed to vent the combined vapours produced in the connected underground storage tanks without exceeding the allowable stresses of the tanks when being filled simultaneously.
(2) Where it is not possible to fill the connected storage tanks referred to in Sentence (1) simultaneously, or where the connected vents have a vapour recovery system, the vent piping shall be sized to accommodate the maximum vapour flow possible in the system.
(3) Vent piping for an underground storage tank containing a Class I liquid shall not be connected to the vent piping for a storage tank containing a Class II or IIIA liquid unless an effective method is provided to prevent the vapours from the Class I liquid storage tank from entering the other tank.
Subsection 4.3.12. Openings Other than Vents in Underground Storage Tanks
Connections
4.3.12.1. Connections for all openings in underground storage tanks shall be liquid- and vapour-tight.
Openings for measuring liquid level
4.3.12.2. Openings for measuring liquid levels in underground storage tanks if independent of the fill pipe shall be equipped with a vapour-tight cap or cover which shall be opened only when measuring the liquid level.
Fill piping and discharge piping
4.3.12.3. (1) Fill piping and discharge piping shall enter underground storage tanks only through the top of the tank and discharge piping used in suction systems shall be sloped toward the storage tanks.
(2) The fill point of an underground storage tank shall not be located higher than the discharge point of the tank’s vent.
(3) Except as provided in Sentence (5), connections used as part of normal operating conditions for filling or emptying storage tanks for flammable liquids and combustible liquids shall be located
(a) outside buildings,
(b) at a location free of sources of ignition, and
(c) not less than 1.5 m away from building openings.
(4) Connections for filling or emptying storage tanks described in Sentence (3) shall be kept closed to prevent leakage when not in use.
(5) A filling connection described in Sentence (3) is permitted to be located inside a building if
(a) this is made necessary
(i) by a process or activity located indoors and to which the storage tank is directly associated, or
(ii) for the collection of used liquids, and
(b) the fill piping is provided with means to prevent flammable vapours from returning to the building.
(6) If a fill piping system has an offset component from the fill point on the storage tank, all fill pipes shall be
(a) double-walled,
(b) sloped to the storage tank, and
(c) electronically monitored for leak detection in conformance with Section 4.4.
(7) Where the fill point is below the normal liquid level in the storage tank
(a) the fill line shall be equipped with a manual or automatic valve located at the fill point to prevent spillage when the fill cap is removed, and
(b) if the storage tank contains flammable liquids or combustible liquids, the fill line drop tube shall be equipped with a method to prevent siphoning of the tank’s content should a leak occur in the fill line.
(8) Fill piping systems that are installed and currently in use, that met the requirements of this Code on December 31, 2025, as it read at the time, and that continue to meet those requirements are deemed to comply with Sentences (6) and (7).
Subsection 4.3.13. Installation of Storage Tanks inside Buildings
Occupancy
4.3.13.1. (1) Except as provided in Article 4.3.13.2., storage tanks located inside buildings shall conform to Subsections 4.3.13. to 4.3.15. and be permitted in
(a) industrial occupancies, and
(b) occupancies other than industrial occupancies where combustible liquids are stored and used as fuel for oil-burning equipment, emergency generators and fire pumps.
Stationary combustion engines
4.3.13.2. Installations using Class I liquids as fuel supplies for stationary engines inside buildings shall conform to NFPA 37, “Installation and Use of Stationary Combustion Engines and Gas Turbines”.
Maximum static head
4.3.13.3. The static head imposed on a storage tank inside a building shall not exceed 70 kPa (gauge) at the bottom of the tank when the vent or fill pipe is filled with liquid unless the tank is designed for greater pressures.
Maximum quantities and location
4.3.13.4. (1) Except as provided in Subsection 4.2.8. and in Sentence (2), storage tanks for flammable liquids or combustible liquids shall be
(a) located in dedicated storage rooms conforming to Subsection 4.3.14., and
(b) located in conformance with Tables 4.3.13.4.A. and 4.3.13.4.B.
(2) When quantities greater than those permitted for incidental use in Subsection 4.2.8. are required for special process operations, storage tanks for flammable liquids or combustible liquids are permitted to be located outside of a storage room referred to in Sentence (1), provided that
(a) total quantities per fire compartment are not more than one-half the quantities permitted in Table 4.3.13.4.A.,
(b) they are located on the first storey, and
(c) the installation conforms to Articles 4.3.13.9. to 4.3.13.12. and 4.3.14.5.
(3) Table 4.3.13.4.A. does not apply to the storage of distilled beverage alcohol.
Table 4.3.13.4.A.
Indoor Tank Storage in Industrial Occupancies Forming Part of Article 4.3.13.4.
| Class of Liquid | Storage Level | Maximum Quantity per Storage Room(1), L |
One or More Tanks
Protected Storage(2)Maximum Quantity per Storage Room(1), L
One or More Tanks
Unprotected StorageClass IFirst storey4000025000Class IStoreys above the first storey7500Not permittedClass IBasementNot permittedNot permittedClasses II and IIIAFirst storey200000100000Classes II and IIIAStoreys above the first storey20000Not permittedClasses II and IIIABasement20000Not permitted
Notes to Table 4.3.13.4.A.:
(1) See Subsection 4.3.14.
(2) See Article 4.2.7.6.
Table 4.3.13.4.B.
Indoor Tank Storage in Occupancies Using Oil-Burning Equipment, Emergency Generators and Fire Pumps Forming Part of Article 4.3.13.4.
| Class of Liquid | Storage Level | Quantity per Protected Storage Room(1), L Individual Tank | Quantity per Protected Storage Room(1), L Aggregate |
| Classes II and IIIA | First storey(2) | > 2500(3) | 200000 |
| Classes II and IIIA | First storey(2) | > 20000(4) | 200000 |
| Classes II and IIIA | Basement and storeys above the first storey | > 2500(3) | 20000 |
| Classes II and IIIA | Basement and storeys above the first storey | > 20000(4) | 45000 |
Notes to Table 4.3.13.4.B.:
(1) See Article 4.2.7.6.
(2) For industrial occupancies where the tanks are located in a separate storage room from the equipment, refer to Table 4.3.13.4.A.
(3) See Sentence 4.3.13.5.(1).
(4) See Sentence 4.3.13.5.(2).
Storage tank construction
4.3.13.5. (1) Storage tanks with an individual capacity exceeding 2500 L but not exceeding 20000 L that are used in conformance with Table 4.3.13.4.B. shall be
(a) of double-walled construction in conformance with CAN/ULC-S601, “Shop Fabricated Steel Aboveground Tanks for Flammable and Combustible Liquids”, and
(b) monitored for leakage in conformance with Sentence 4.4.2.1.(7).
(2) Storage tanks with an individual capacity exceeding 20000 L that are used in conformance with Table 4.3.13.4.B. shall
(a) conform to ULC-S655, “Aboveground Protected Tank Assemblies for Flammable and Combustible Liquids”, and
(b) be monitored for leakage in conformance with Sentence 4.4.2.1.(7).
Piping systems
4.3.13.6. Piping systems serving oil-burning equipment, diesel-engine-driven emergency generators and fire pumps shall conform to CSA B139, “Installation Code for Oil-Burning Equipment”.
Fire compartments
4.3.13.7. Fire compartments regulated by this Subsection shall be separated from the remainder of the building by a fire separation having a fire-resistance rating of not less than 2 h.
Mixed storage
4.3.13.8. When two or more classes of liquids are stored in a single storage room referred to in Sentence 4.3.13.4.(1), the total quantity permitted for each class of liquid shall be calculated as follows:
qI / QI + (qII + IIIA) / (QII + IIIA) ≤ 1
where
qI = actual quantity of Class I liquids present, in litres,
qII + IIIA = actual quantity of Class II and IIIA liquids present, in litres
QI = maximum quantity of Class I liquids permitted in Table 4.3.13.4.A., in litres, and
QII + IIIA = maximum quantity of Class II and IIIA liquids permitted in Table 4.3.13.4.A., in litres.
Storage tanks outside storage rooms
4.3.13.9. (1) Where storage tanks for flammable liquids or combustible liquids are located outside of storage rooms conforming to Subsection 4.3.14.
(a) provision shall be made to contain a spill equal to at least 100% of the volume of the largest storage tank, or to drain away spilled flammable liquids or combustible liquids, in conformance with Subsection 4.1.6.,
(b) the area in which the storage tank is located shall be ventilated in conformance with Subsection 4.1.7., where designated a Class 1, Zone 0, 1 or 2 hazardous location under the Electrical Safety Code made under the Electricity Act, 1998, and
(c) all electrical equipment and wiring in the vicinity of the storage tank and the exterior vent shall be installed in conformance with Subsection 4.1.4.
Vents
4.3.13.10. (1) Except as provided in Sentence (2), normal and emergency vents for storage tanks in buildings shall be provided in conformance with Subsections 4.3.4. and 4.3.5.
(2) The use of weak roof-to-side shell seams, designed to rupture before the allowable design stress of the storage tank is reached, shall not be permitted as a means of emergency venting of storage tanks inside buildings.
Supports, foundations and anchorage
4.3.13.11. (1) Except as provided in Sentence (2), where storage tanks for flammable liquids or combustible liquids are installed inside buildings, the supports, foundations and anchorage for such storage tanks shall be in conformance with Subsection 4.3.3.
(2) Where a storage tank is suspended, rather than supported on a foundation, supports shall be designed and installed in conformance with good engineering practice.
Bonding and grounding
4.3.13.12. Where storage tanks for flammable liquids or combustible liquids are installed inside buildings, tanks, piping and discharge equipment shall be bonded and grounded.
Subsection 4.3.14. Rooms for Storage Tanks
Design and construction
4.3.14.1. (1) Rooms for storage tanks inside buildings, referred to in Sentence 4.3.13.4.(1), shall be
(a) separated from the rest of the building by a fire separation having a fire-resistance rating of at least 2 h,
(b) designed to contain a spill equal to at least 100% of the volume of the largest storage tank or to drain away spilled flammable liquids or combustible liquids,
(c) made liquid-tight where the walls join the floor,
(d) used for no other purposes than the storage and handling of flammable liquids or combustible liquids, and
(e) provided with natural or mechanical ventilation in conformance with Subsection 4.1.7.
Clearances
4.3.14.2. A minimum clear space of 550 mm shall be maintained between the walls of a room described in Article 4.3.14.1. and the sides of any storage tanks within the room.
Explosion venting
4.3.14.3. Where Class IA or IB liquids are dispensed within a storage room, the room shall be designed to prevent critical structural and mechanical damage from an internal explosion in conformance with NFPA 68, “Standard on Explosion Protection by Deflagration Venting”.
Placards
4.3.14.4. (1) Placards conforming to Article 3.2.7.14., identifying the liquids stored as flammable liquids or combustible liquids and the capacities of the storage tanks, shall be posted in a conspicuous location outside of the room, and that information shall be included in the fire safety plan required in Article 4.1.5.5.
(2) Placards that are installed and currently in use, that met the requirements of this Code on December 31, 2025, as it read at the time, and that continue to meet those requirements are deemed to comply with Sentence (1).
Hose stations and portable extinguishers
4.3.14.5. (1) In buildings not required to be equipped with a standpipe and hose system by the Building Code, hose stations conforming to Articles 3.2.9.2. to 3.2.9.7. of Division B of the Building Code, as it read on August 21, 2000, shall be provided in the vicinity of the storage room, such that all parts of the room are within reach of a hose stream.
(2) Portable extinguishers for Class B fires shall be provided in conformance with Section 6.2.
Subsection 4.3.15. Openings Other than Vents in Storage Tanks inside Buildings
Connections
4.3.15.1. (1) Connections for all openings in storage tanks in buildings shall be liquid- and vapour-tight.
(2) Connections to storage tanks through which liquid can flow shall be provided with valves located as close as practicable to the tank.
(3) Connections for filling or emptying storage tanks shall be provided with a spill containment device in accordance with Sentence 4.3.6.4.(4).
Openings for liquid level measurement
4.3.15.2. (1) Openings that are independent of the fill pipe and are used for measuring the liquid level in storage tanks containing Class I or II liquids shall be equipped with a vapour-tight cap which shall be opened only when measuring the liquid level.
(2) Openings referred to in Sentence (1) shall be protected against overflow and vapour pressure by means of a spring-loaded check valve.
Subsection 4.3.16. Out of Service
Underground storage tanks
4.3.16.1. (1) The removal, abandonment in place, disposal or temporary taking out of service of an underground storage tank shall be in conformance with
(a) NFPA 30, “Flammable and Combustible Liquids Code”,
(b) API RP 1604, “Closure of Underground Petroleum Storage Tanks”, or
(c) CCME PN 1326, “Environmental Code of Practice for Aboveground and Underground Storage Tank Systems Containing Petroleum and Allied Petroleum Products”.
(2) Where a storage tank has been out of service for more than 12 months, the tank and piping shall be tested for leakage in conformance with Section 4.4.
(3) Underground storage tanks that were abandoned in place or temporarily taken out of service, that met the requirements of this Code on December 31, 2025, as it read at the time, and that continue to meet those requirements are deemed to comply with Sentence (1).
Removal
4.3.16.2. (1) In addition to the requirements of Article 4.3.16.1., when underground storage tanks have no further use or have been out of service for two years or longer, such tanks, together with connected piping and dispensers, shall
(a) have all flammable liquids and combustible liquids removed from them,
(b) be purged of vapours, and
(c) except as permitted in Article 4.3.16.3., be removed from the ground.
(2) If contaminated, soil surrounding the storage tanks described in Sentence (1) shall be replaced with clean fill.
Abandonment in place
4.3.16.3. (1) In addition to the requirements of Articles 4.3.16.1. and 4.3.16.2., where the Chief Fire Official determines that it is impractical to remove an underground storage tank described in Sentence 4.3.16.2.(1), such tank shall be filled with an inert material.
(2) In addition to the requirements of Articles 4.3.16.1. and 4.3.16.2., where the Chief Fire Official determines that it is impractical to remove underground piping described in Sentence 4.3.16.2.(1), such piping shall have the ends permanently sealed by capping or plugging.
Aboveground storage tanks
4.3.16.4. (1) When an aboveground storage tank will be out of service or unsupervised for a period not exceeding 180 days, the piping from the tank shall be capped or the valves that are necessary to achieve similar isolation of the tank shall be closed and securely locked.
(2) Where a storage tank referred to in Sentence (1) contains flammable liquids or combustible liquids, the liquid level in the tank shall be measured and compared with subsequent readings taken at intervals not greater than one month.
(3) When an aboveground storage tank will be out of service or unsupervised for a period exceeding 180 days
(a) all liquid and vapours shall be removed from the storage tank and its connected piping, and
(b) the storage tank markings shall clearly indicate that the tank is empty.
Disposal
4.3.16.5. Where a storage tank is to be permanently disposed of, sufficient openings shall be cut in the tank to render it unfit for further use.
Underground piping systems
4.3.16.6. (1) The removal, abandonment in place, disposal or temporary taking out of service of an underground piping system shall be in conformance with
(a) NFPA 30, “Flammable and Combustible Liquids Code”,
(b) API RP 1604, “Closure of Underground Petroleum Storage Tanks”, or
(c) CCME PN 1326, “Environmental Code of Practice for Aboveground and Underground Storage Tank Systems Containing Petroleum and Allied Petroleum Products”.
Corrosion protection
4.3.16.7. Corrosion protection systems shall be maintained in operating condition when a storage tank is temporarily out of service and during seasonal shutdowns.