Why it matters
This is one of the few home issues that can become a very large environmental liability. A leak means soil and groundwater contamination, and the property owner is generally responsible for the cleanup, which can run from ten thousand to well over a hundred thousand dollars. Just as important: many insurers refuse to write or renew a policy on a home with an old or buried oil tank, or require it to be replaced or removed first, which can also affect your mortgage. Buried tanks are the bigger worry because they're hidden and hard to assess.
How to spot it
An oil tank in the basement or beside the house; fill and vent pipes poking out of the ground or an exterior wall (a sign of a possible buried tank, even if the visible tank is gone); oil staining or a petroleum smell. Ask the seller directly about the tank's age and type, and whether a buried tank was ever on the property and how it was removed, and get documentation.
What it costs
Replacing an aboveground tank runs roughly $2,500 to $5,000. A buried tank is two different jobs at two different prices. Full removal, which in Ontario must be done by a TSSA-registered petroleum contractor and involves excavation and site restoration, commonly runs $3,000 to $6,000+, with a typical 500-gallon steel tank at the upper end and a smaller, easily-accessed tank lower. Decommissioning in place, draining, cleaning, and filling the tank, runs $600 to $3,400, but it is not always an option: many jurisdictions require a tank that is out of service to be removed rather than abandoned, so confirm what your municipality and the TSSA actually permit before you budget the cheaper number. Soil testing adds a few hundred dollars. But if the tank has leaked, environmental remediation can run $10,000 to $100,000+, which is exactly why this is a before-you-buy issue, not a later one.
What to do
Address before purchase. Confirm the tank's age, type, and insurability with your broker before you remove your conditions. For a buried or suspected buried tank, get a professional tank assessment or soil test rather than assuming it's fine. Budget accordingly and use any finding as a negotiation point, or make removal a condition of the sale. Use a licensed oil-tank or environmental professional.
Education and triage, not a home inspection. Casaroo flags signs of an oil tank, a basement tank, or fill and vent pipes, from photos; a licensed tank or environmental professional confirms its condition and whether any contamination exists. We flag; we don't inspect.