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Above-Ground Oil Tanks

Fill valve on rusty oil tank

In many regions across Canada—particularly in Quebec and the Atlantic provinces—above ground oil tanks are still being used to heat institutional and commercial properties, in addition to private homes.

While mostly a safe and effective heating method, above ground oil tanks present a number of risks, among them:

  • Fire
  • Theft
  • Tank, line or fitting failures
  • Oil leaks and spills due to wear and tear or over fill

Over time, oil tanks can deteriorate due to water damage that causes internal corrosion, resulting in oil leaks and spills that pose potential pollution and environmental risks. A leaking tank can contaminate wells and drinking water, soil and groundwater, storm water drains, sewers and drainage ditches, as well as streams, rivers and lakes. It can also cause unpleasant odours and lead to health problems in neighbouring homes and businesses.

When a leakage occurs, oil remediation is not only difficult, it is expensive. To help prevent oil leaks and spills, protect the environment and avoid unnecessary costs, it is important to understand the risks associated with oil tanks, ensure installations are done correctly, and take the appropriate steps to monitor and maintain the tanks.

The following are best practices for the care, maintenance and replacement of above ground heating oil tanks.

A full 275-gallon tank weighs over 2,000 pounds… one litre of leaked oil can contaminate up to one million litres of drinking water.

Inspection and Maintenance

To prevent costly and environmentally damaging leaks or spills, be sure you follow local regulations and codes of practice. Schedule a maintenance check-up by a Certified Oil Burner Mechanic in the fall before the peak heating season. Check the tanks in the spring to ensure there was no damage from the harsh winter weather, and inspect the tank throughout the year.

Inspection and maintenance steps include:

  • Check the bottom of the tank for holes or rough areas that may indicate holes are forming—pinholes can cause a slow leak resulting in a significant loss of oil. Also check the fuel delivery line, valves, piping and fittings.
  • Check for water in the tank by applying a water-finding paste to a clean stick (minimum 4 feet long) and dipping it into the tank through the filler pipe. The outside bottom corner of the tank beside the oil supply line will slowly turn black if there is water corrosion.
  • Remove snow from beneath outdoor tanks following a storm and carefully clean off the fittings and oil line to prevent a build-up of snow or ice.
  • Protect exposed oil lines with a durable hard plastic cover (PVC or similar) over the line between the tank and the building to prevent damage by falling ice, snow or vandalism.
  • Check the vent whistle which increases in pitch as the oil level nears the top to warn that the fuel is approaching capacity, a common source of spills.
  • Install an oil safety valve/anti-siphon valve to automatically shut-off the flow of oil from a tank if the line between the valve and oil burner is broken or severed, and prevent oil from being siphoned out of the tank.
  • Check the stability of the tank—this can be done by your oil company. If the metal legs become loose or the pad they are sitting on cracks, the tank can topple and potentially rupture.
  • Have the oil tank cleaned out at least every 10 years. Water and sludge can lead to internal corrosion and cause leaks.

Tank Replacement and Installation

Choose an interior tank if possible to avoid exposure to external elements. It is also easier to detect leaks or early warnings of a leak on interior tanks.

Outdoor oil tanks are exposed to extreme temperatures, ice, snow, rain, condensation, vandalism, and can be damaged by severe weather if not properly protected. Snow storms, ice falling from roofs and eaves, and freezing rain that can bring down tree limbs can puncture tanks and sever supply line connections, causing a spill or leak.

When installing an outdoor tank, be sure it is not positioned under the building eaves, and that there is room around the tank for a full inspection. Here are additional best practices for tank replacement and installation.

Oil tank purchase

Look for a label on the top or side the new oil tank, providing information on the manufacturer, date of manufacture, and that it meets Underwriters’ Laboratories of Canada (ULC) or Canadian Standards Association (CSA) standards of construction and/or the National Standard of Canada (CAN4-S602-M81).

Longer lasting tanks

Choose from double walled tanks, fibreglass tanks, composite plastic/metal tanks, lined tanks, and heavier walled 2.5 mm (12 gauge) steel tanks. Double wall tanks with 110% containment volume and an alarm if the inner wall is perforated are recommended.

Tank installation

Hire a professional contractor to install the tank in accordance with installation standards (CAN/CSA-B139) and the National Fire Code. Installation by a trained installer will also validate any warranty.

CAN/CSA-B139 applies to above-ground storage tanks that have a maximum individual capacity of 2,500 litres (550 gallons) and a maximum aggregate capacity of 5,000 litres (1,100 gallons). Above ground installations over 2,500 litres are covered by the National Fire Code of Canada and Canadian Council of Ministers of the Environment Environmental Code. Storage tank installation may also be governed by the authority having jurisdiction.


  • Install bottom outlet tanks with a decline of ¼ inch per foot of tank length to ensure water is removed and the feed line does not freeze.
  • Install exterior tanks downgrade of domestic drinking water.
  • Position exterior tanks so a spill will drain away from the building foundation.
  • Position all tanks to allow room for visual inspection of the top, bottom, sides and ends, and the application of protective coatings to all areas of the tank.


  • Install a used or refurbished tank.
  • Drop or drag a tank.
  • Install exterior tanks directly under eaves to protect from falling snow, ice, and drips.

Interior tanks

In addition to the points above, follow these guidelines for interior tanks:

  • Place on a concrete floor to provide a stable, level base.
  • Locate the tank on the lowest floor of the building, or if in a garage, protected from possible impact.
  • Install interior tanks at least 12 inches from the wall.
  • Install tanks at least 5 feet (1.5 metres) from fuel fired appliances (check with local municipal building code authorities for variances in this requirement).
  • If there are multiple tanks, ensure they are at least 12 inches from each other.

Oil transfer

Avoid transferring product from an old tank to a new tank.


Install padlocks fitted to the filler pipe on exterior and interior oil tanks with exposed filler pipes to avoid theft of oil from the tank.

Valve protectors

Prevent exterior access with valve protectors bolted on to cover the fittings/valves.


Use a locked fence of wire mesh or heavy timber fabric to protect the oil tank from flying objects and malicious damage.

Drip trays/Catch-pits

Reduce the risks of fire and pollution with a catch-pit, or place a drip tray under the tank. The catch-pit or drip tray should be constructed of an impermeable material such as concrete, non-porous engineering bricks on a concrete base, or solid steel, and have the capacity to hold the contents of the tank(s) plus 10%.

Fusible links

Install a fusible link to automatically close the oil supply in case of fire.

Life Span

Ecclesiastical Insurance recommends the following life spans for oil tanks:
Type of Tank Replacement Indoor Replacement Outdoor
Steel, 14 gauge (2.0 mm), single wall; end or top outlet 15 years 10 years
Steel, 14 gauge (2.0 mm), single wall; bottom outlet 20 years 15 years
Steel, 12 gauge (2.3 mm), single wall; end or top outlet 20 years 15 years
Steel, 12 gauge (2.3 mm), single wall; bottom outlet 25 years 20 years
Steel, double walled, 110% containment 30 years 25 years
Fibreglass, single or double wall 30 years 30 years
Galvanized steel with liner (eg. Roth) 30 years 30 years

Some provinces and territories have their own guidelines and these should be consulted before replacing any tank.


If a leak occurs, immediately take all reasonable steps to stop the leak and prevent further damage. Report any leaks to your fuel supplier or burner service company. Spills over a specific number of litres have to be reported to the Department of Environment having jurisdiction in the province. When in doubt, always report a spill to your local authority or Department of Environment.

By understanding the risks and taking the appropriate steps to manage them, we can help reduce the potential of an oil spill and the significant losses that result—monetary, environmental and the hardship that results from a disruption to your services and your communities of interest.

This advice or information is provided in good faith and is based upon our understanding of current law and practice. Neither Ecclesiastical Insurance Office plc nor its subsidiaries accepts any liability whatsoever for any errors or omissions which may result in injury, loss or damage, including consequential or financial loss. It is the responsibility of the Insured or any other person to ensure that they comply with their statutory obligations and any interpretation or implementation of the above is at the sole discretion of the Insured or other party who may read these notes.

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