Uncovering an Old Underground Oil Tank
iStock.com / jonathansloane

Abandoned underground heating oil tanks aren’t uncommon on older properties, but a standard home inspection won’t tell you if one is hidden on the property you’re looking to buy. An oil tank sweep is designed to locate any hidden tanks, so you don’t end up suffering the health and financial consequences of an oil leak.

The Danger of Forgotten Oil Tanks

An Excavator Grabbing a Rusty Oil Tank
iStock.com / nycshooter

Oil heating was common between the 1930s and the 1980s, particularly in the Northeast, so any home built during this time could have an oil tank somewhere on the property. While homes built before and after this period are less likely to have used oil heating, it’s still a possibility. Many real estate purchase contracts include a clause that covers oil tanks, but not all do. Some homeowners have no idea a tank is buried on their property.

If you’re unsure about the property you’re considering, having an oil tank sweep done lets you know if a tank is present so you can make an informed decision.

An underground oil tank hidden on your property is a serious issue that could leave you with expensive problems. Old tanks often contain oil that can leak for a variety of reasons, including tank corrosion and mechanical failure. Old, unmaintained tanks are especially likely to leak. Because home heating oil contains benzene, a known carcinogen, it contaminates any soil or groundwater it contacts.

Larger leaks can contaminate local aquifers and neighboring properties. Leaks can go undetected for years, gradually worsening until the homeowner discovers it by chance when they decide to build an addition, outbuilding, or in-ground pool.

Even if no oil escapes, vapors still can. These toxic gases can irritate your eyes, nose and throat, and cause headaches, dizziness, and nausea. They’re also flammable and can combust if they come into contact with an open flame or spark.

If a tank on your property leaks oil or vapors, you’ll be legally liable for the clean up, and it isn’t a job you can handle yourself. Cleaning up a leaky oil tank is a hazardous material remediation job that requires trained, certified professionals.

Beyond that, you might need to obtain a construction permit to remove the tank, have the contaminated soil shipped to an appropriate facility, and order certified laboratory tests to ensure your soil and water are safe. The cost can run from a few thousand for a small spill that was caught quickly to several hundred thousand for extensive spills. You might also end up facing lawsuits from neighbors affected by the leak.

Most homeowner’s insurance policies don’t cover oil tank leaks, so if you don’t have a separate tank insurance policy, you could end up paying out of pocket. No matter how well it’s cleaned up, an oil leak can lower your property value and make selling harder. Even if you live for years completely unaware of the old tank, if you decide to sell, there’s a good chance your potential buyer will order an oil tank sweep, and you’ll have to deal with the problem then.

What to Expect From an Oil Tank Sweep

Removing a Residential Underground Oil Tank
iStock.com / jonathansloane

Some cheaper oil tank sweep services use only a metal detector, but this isn’t very efficient. A metal detector can find metal, but it can’t tell you if that metal is an oil tank or some old hubcaps.

To ensure any oil tank on the property is found, choose a service that uses several detection methods. These services typically start with the technician performing a visual inspection of the home’s exterior and interior for signs an oil tank was used in the past.

If the house has an old oil furnace, shut off switches, an unused fill pipe and vent pipe, holes in the foundation or basement walls, or pipes protruding from the ground, it probably had or still has an oil tank. These signs also help the technician locate the tank. A fill pipe placed far from the vent pipe suggests the tank was buried in the yard rather than installed in the basement.

Next, the technician scans the ground around the perimeter of the house. Most oil tanks are buried within 15 feet of the house, so there’s no need to sweep the whole property.

One of the most common types of equipment for this step is a ground penetrating radar (GPR) system, which creates an electromagnetic signal that can detect buried objects through soil, concrete, and asphalt as far as 20 feet down. The GPR display screen shows the technician a rough image of the object, so they can tell if it’s a tank or something else.

During this stage, the technician might also physically probe the soil with a rod to feel for any buried objects. The GPR scan is often followed with a scan using a ferromagnetic (FM) detection system to confirm that the object found is metal.

If your oil tank sweep does turn up an oil tank, ask the seller if they have tank insurance they can transfer to you. If the tank isn’t covered by insurance, have it tested and insured before you close on the house. This process will reveal any leaks. Alternatively, the seller might decide to have the tank removed or sealed at their own expense, in which case you’ll need documentation of the process.

If you discover an oil tank on your property after you buy, check your real estate contract for a clause requiring the seller to disclose information about any oil tanks on the property. If you find such a clause and the seller failed to tell you about the tank, they’re in breach of contract, and you could have grounds for a lawsuit. Without this contractual obligation, though, removing or insuring the tank is your responsibility.

The health and environmental risks a forgotten heating oil tank poses shouldn’t be ignored. If you’re planning to buy or you’ve already bought an older property, an oil tank sweep will let you know if an old tank is lurking under the lawn so you can take action before you end up with an expensive mess.

Editorial Contributors
Henry Parker

Henry Parker

Henry Parker is a home improvement enthusiast who loves to share his passion and expertise with others. He writes on a variety of topics, such as painting, flooring, windows, and lawn care, to help homeowners make informed decisions and achieve their desired results. Henry strives to write high quality guides and reviews that are easy to understand and practical to follow. Whether you are looking for the best electric riding lawn mower, the easiest way to remove paint from flooring, or the signs of a bad tile job, Henry has you covered with his insightful and honest articles. Henry lives in Florida with his wife and two kids, and enjoys spending his free time on DIY projects around the house. You can find some of his work on Today’s Homeowner, where he is a regular contributor.

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