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How do I know if my underground heating oil tank is leaking?

Many residents use heating oil to heat their homes and, unfortunately, most residential heating oil tanks are 50-70 years old. Leaks can occur when tanks get this old, but there are some simple ways to determine if your tank is leaking:

Track your oil use. If your furnace seems to be using unexpected/unexplained more fuel oil consumption and the weather hasn’t justified an increase, your tank may be leaking.

Sometimes a tank will contain oil and water, or primarily water (the water will settle to the bottom; the oil will float on top). To check for water, put a small amount of water-reactive paste on the end of a tape measure and insert it into the storage tank. If water is present, the paste will change color. Any amount of water present should be investigated further because if water is getting in through a hole in the tank, oil is almost certain to be getting out.

During the summer, when you’re not using your furnace, turn off your furnace, measure the level of oil in your fuel tank using a tape measure or some other measuring device. After a few weeks, measure it again. If the level is lower, then the tank is probably leaking.

If you smell oil around the tank, near your property’s catch basins or in your basement, the oil may have leaked from your tank. It may also have infiltrated to the bedding area of nearby underground pipes and found a drainage course into the groundwater or surface water. Residential heating oil is dyed a red color which makes it easily identifiable.

What if my tank has a leak?

If you find that your tank has a leak, you should take immediate action to stop the leak. Call Seattle Tank Services and we can assist you.

No longer using your tank and have an abandoned heating oil tank?

If you have switched from home heating oil to natural gas or electricity as a means of heating your home, and your heating oil tank is no longer in use, then it’s a good idea to have it decommissioned. It is especially a good idea if you plan on selling the house. Often, home buyers and lending institutions require assurance that the property being sold is not contaminated; and the best way to do that is to remove the tank and sample the surrounding soil. If removal isn’t possible, and you don’t expect to sell the house, you can decommission your home heating oil tank by “close your tank in place” by pumping out the oil, triple rinsing it, and filling the tank with inert solid material.

Have all unused heating oil removed from your tank

The Washington State Department of Ecology strongly recommends that you have all unused heating oil removed from your tank. Removing the unused oil is the easiest, least costly, and single-most important action you can take to prevent contamination of soil and groundwater. After the heating oil has been pumped out of your tank, you should think about having your tank removed or “closed in place.”

What is the life expectancy of underground oil tanks?

While some underground heating oil tanks have lasted longer, a common life expectancy of buried underground oil tanks is approximately 10-15 years. The odds of a leak happening increase, as the tank gets older. Even small, slow leaks can pose a significant risk to the environment if they go undiscovered for a long time. The best way to avoid potential problems associated with a leaking tank is to have your tank taken out of the ground and have a new tank installed, either underground or aboveground.

What is an “abandoned” underground storage tank?

Many underground storage tanks are no longer being used, rendered obsolete by piped-in natural gas or electric baseboard heat or heat pumps. An underground storage tank that is no longer in use is considered “abandoned.”

What should be done with an abandoned underground storage tank?

The Washington State Department of Ecology recommends and many Local Fire Departments require permanent closure for abandoned underground storage tanks. The process of permanently closing a tank is referred to as “decommissioning.” A tank may be decommissioned by filling it with an inert material such as slurry, foam, sand or by removing it from the ground. Decommissioning also involves removing heating oil and sludge from the tank.

Many underground storage tanks have been abandoned with oil still in them. You should consider arranging to have any remaining oil removed from the abandoned tank if you do not immediately decommission it. This will help prevent possible contamination of soil and groundwater.

Why should I decommission my abandoned underground storage tank?

Abandoned underground storage tanks are a potential source of contamination of the soil and groundwater. They should be de-commissioned whenever they are no longer used or whenever there are questions about their structural integrity or about their ability to hold product without leaking.

Under the Model Toxics Control Act, a tank owner may be held liable for contamination caused by a leak.

Many times the tank does not become an issue until the homeowner decides to sell their home and at that time has an inspection done on their home. These inspections are often done one to two weeks before closing. Before finalizing the sale of a house, lending institutions and home buyers may want sellers to remove or decommission the abandoned heating oil tank.

For more information on Seattle’s new oil tank laws, click here.

Is there a problem if I have an abandoned tank on my property?

Discovering an abandoned tank on your property doesn’t mean that it has leaked or caused an environmental problem. Even a leaking abandoned tank does not necessarily pose a health risk because most leaks are usually small and localized. Although most abandoned underground oil storage tanks do not cause major environmental problems or health risks, ignoring an abandoned oil tank is not recommended. Even if it has not yet caused a problem, it could in the future.

Dealing with your tank now may prevent or at least minimize future problems and expense. Some abandoned heating oil tanks have leaked heating oil, resulting in contaminated soil and groundwater and expensive cleanups. Leaking oil can migrate into a basement or crawl space of your home and, although unlikely, the fumes from the oil could cause a fire or health risk.

How do I know to locate or know if I have an oil tank on my property?

Most underground residential tanks are easy to find. If you have trouble locating your tank, try following the fuel lines from the house, locating the tank vent pipes, or use a hand probe or metal detector. All oil tanks must have a fill and vent pipe. Capped pipes coming in the basement furnace walls are another sign. If you’re still not sure call Seattle Tank Services and we can offer easy to understand oil tank location tips over the phone. If you need more help, we will bring our high powered metal detecting equipment to locate any abandoned underground heating oil tank or home heating fuel lines on your property.

How do I know if the previous owners had the tank decommissioned?

Call Seattle Tank Services 206-938-2280 and we can check for you.

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