Things you should know about heating-oil tanks


Steel oil tanks corrode from the inside out due to action by microbes.

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Microbes are living organisms so small they can only be seen under a microscope. They are found practically everywhere, in the air and water.

Water from condensation inside a tank gives rise to both aerobic and anaerobic bacteria. The oil becomes both a food source and a welcome environment for the microbes to grow and multiply. This growth forms into a sludge that sits at the bottom of the tank.

The sludge is both acidic and corrosive, attacking the metal tank. It can also be sucked up by the home's furnace, leading to corrosion in the fuel lines and the burners of the furnace.

Prevention of bacterial growth requires regular water removal, filtration and/or the treatment of the tank with additives.

Condensation occurs more frequently on tanks situated outside a home, due to constant changes in temperature. A tank exposed to the sun often incurs more condensation than those that sit in the shade.


Steel tanks should be replaced every 15 years. Tanks manufactured within the past 10 years have a plaque attached, noting the year of manufacture. If a plaque cannot be found, it is likely to be more than 10 years old and caution should be taken.


If outside, the tank should be mounted on a concrete slab and vegetation kept away. A homeowner should occasionally check the ground beneath the tank for signs of oil. The smell of diesel fumes in the house or in the area where the tank is located should be a red flag to homeowners that something is amiss. On smelling such fumes, the homeowner should call in a licensed professional to diagnose and remediate the problem.


While very rare, there may still be some oil tanks buried in the ground. While many have been decommissioned, they can still be dangerous. They can fill with water and slowly leak into the soil. Some have been known to rust and collapse, resulting in a sinkhole on the property.


Even after cancelling oil delivery service, homeowners should ensure that the filler tube of an oil tank is removed along with the tank. Problems occur when an oil company mistakenly delivers a load of oil to a house after a tank has been removed. A few hundred litres of oil pumped into a newly renovated basement can cause tens of thousands of dollars in damage. A temporary solution is to affix or adorn a filler cap with warnings of the tank's removal.

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