Photograph of sketch of parts of a buried oil tank Buried fuel oil tanks
Advice for home owners, buyers, inspectors

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Buried oil storage tank (UST) advice for building owners & buyers:

This article explains residential and light commercial buried oil tanks or other buried heating fuel tanks: environmental concerns, defects, inspection: basic advice for home buyers and home owners where a buried oil tank is or was installed.

We discuss the risks regarding buried oil storage tanks USTs or other buried tanks. We include photographs, a field report of a severe heating oil tank leak into the building, and commentary on detecting leaks or threats of leaks at buried oil storage tanks.

This document provides sample home inspection report language which may assist in advising home owners or home buyers about the risks associated with buried oil or other fuel storage tanks at their property, and which can help explain the need for action and where more information can be obtained.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

The Buried Oil Tank RIsk: A Home Buyer's Guide to Buried Oil Tanks - The Risk of Oil Leaks Means Risk of Major Cleanup Costs

Pipe indicates buried oil tankIf you are purchasing a property where there is or was an oil storage tank that has been abandoned or removed, you should be sure to read HOME BUYERS GUIDE TO OIL TANKS.

When we observe evidence that a buried fuel storage tank is [or may have previously have been] located at a property and when no other information is known about the type, condition, or even exact location of the tank, underground tank leaks, environmental damage, local water or well contamination, and a costly cleanup are potential risks to the property owner.

See REPORTING BURIED OIL TANKS for suggestions of how to report suspected or actual evidence of USTs at a property.

Because significant site cleanup costs can be involved if an oil tank has leaked at a property, unless there is reliable documentation that the tank has been tested quite recently, it would be prudent for a home buyer to have such testing performed before purchasing the property.

Installing a new oil storage tank will involve significant expense.

There are also proper methods of "abandoning" old unused buried tanks. Requirements for reporting oil tanks at properties and for reporting heating oil leaks when they are discovered are discussed next, followed by our advice regarding tank inspection, testing, and detection. (C)Copyright trap DJ Friedman.

Before completing purchase of a property that has or had a buried oil tank you need to have either had the tank removed, abandoned in place, or tested. The discussion which follows explains the risks and gives detailed advice about what to do about buried or above ground oil tanks and tank leaks.

See REPORTING BURIED OIL TANKS for suggestions of how to report suspected or actual evidence of USTs at a property.

Summary of Oil Leak Reporting Requirements & Oil Tank Registration at Residential Properties

Oil spill in a basementThe NYS Department of Environmental Conservation, which has regulations similar to those of most U.S. states, has a program requiring the registration of buried tanks at any site storing more than 1100 gallons of heating oil.

Though specific reporting details may vary, most U.S. states have similar requirements. Requirements for gas (auto fuel), or other fuels may be different as well.

The presence of a buried (or above ground) oil storage tank at a residential property does not need to be reported to the DEC provided the onsite storage volume is less than 1100 gallons.

However, if an oil leak is detected at any fuel storage tank, indoors, outside above ground, or buried, it must be reported to the Department of Environmental Conservation within two hours. The concern is for leaks which contaminate the environment.

Tanks located where they may leak into a local waterway or into the water supply are a special environmental concerns.

Using a second U.S. state, Maryland, as example, if soil or groundwater contamination is found during oil tank (or presumably any other) excavation, the contamination must be reported to Maryland Department of the Environment immediately upon discovery.

Any residential heating oil storage tank greater than 1,100 gallons in capacity must be required to be registered with MDE.

Heating oil tank regulations vary widely in other U.S. states and in other countries. According to Project Clean Oslofjord in Norway, maintenance checks of buried oil tanks are required initially only to tanks over 3,200 liters.

For oil tanks within the regulated size range, since 1997 owners of such oil storage tanks must have the tanks checked at a frequency that depends on tank type: single- or double-bottomed steel tanks the first check is after 15 years. After the initial test, such tanks shall be checked every fifth year.

For less leak-prone fiberglass tanks (glass fibre reinforced polyester) the tanks must be pressure-tested two years after burial, and afterwards at 30 years.

OIL TANK REGULATIONS provides a detailed review of oil leak reporting requirements by U.S. state and other areas and provides links to various tank abandonment regulations

How to Find Evidence of Buried Oil Tanks at a Property

Piping indicating an abandoned oil tank

Often an astute inspector can find evidence that there is or still remains a buried oil storage tank at a property even when the fill and vent pipe have been removed and when there is no advance-notification that such a tank was ever present.

Our photo at left was taken in the basement of a home in Portland Maine built around 1900. We see the following items:

Not shown in the photo was a new oil tank installed in this basement.

With just the evidence at hand, we don't know if the prior oil tank which was served by these oil lines was indoors or outdoors. In fact, following the floor cut to the building foundation wall it was easily apparent that the original lines had penetrated the foundation wall to head outside.

This home was previously served by an outdoor underground oil tank or UST.

We still haven't determined if the old oil tank has been properly abandoned or removed - further investigation is in order.

Visual Evidence of Buried Oil Tanks Previously in Use, Possibly Abandoned at a Site

There are many visual clues that will tell us that an oil tank has been in use and abandoned at a property.

Study the photographs that follow for more examples of how to look for evidence of a buried oil tank.

For older properties in areas where use of oil as a heating fuel was common, inspect the building grounds for oil fill or vent pipes. Sometimes an oil filler may be distant from the home, depending on where it was convenient to bury an oil tank; sometimes the oil vent pipe may be nowhere near the oil filler pipe.

Sometimes unscrupulous sellers or agents remove the fill or vent piping from a buried oil tank, taking no other action to properly abandon in place or remove the tank. Don't be afraid to lift flat stones or paint or coffee cans that may be marking an old oil tank filler or vent pipe.

For below-ground oil tanks or USTs, a visual inspection inside of the in-building equipment, foundation walls, and surrounding area may disclose abandoned oil lines, marks where such lines were present, or older gauges or valves used with an outdoor buried oil tank.

For above-ground tanks, a simple visual inspection of the tank and its piping, can give you and idea of the risks involved. Look for obvious leaks such as oil stains on the ground or floor under or around the tank and around the oil fired equipment. Remember to look under the oil tank at its bottom, as most leaks occur in the lower portion of the tank.

Non-Visual Evidence of Buried Oil Tanks Previously in Use, Possibly Abandoned at a Site

Buried Tanks: Look at the property before deciding to hire a tank testing company for professional inspection and testing. You can obtain basic information such as the age (property and tank), tank location, and type of oil tank. From a previous use, a buried oil tank may be present or may have been present at a property even if it is now served by an indoor, above ground oil tank or even by LP or natural gas.

So don't assume that because you don't see a tank that none was ever used or present at a property.

Make a visual site inspection for clues suggesting that one or more tanks is or was present.

Even when there are no direct visual clues, contextual inspecting and thinking about the history of a building may still suggest that it had or may have had a buried oil tank with sufficient probability that it is worth further investigation to search for a buried tank, or for records indicating that an oil tank has previously been removed. These include:

More on How to Find Oil Storage Tanks at a Property:

Field Report: Photo Tour of Severe Oil Leak into an Older Home

Outdoor site photo showing the filler pipe for a buried oil storage tank or UST of unknown size (C)  and  ASHI inspector Lawrence Transue Dec 2017These photographs of severe leakage of heating oil into a home were provided courtesy of ASHI home inspector Lawrence Transue. Mr. Transue is a certified ASHI home inspector and holds other construction credentials as well.

The inspector was engaged to inspect this Pennsylvania property approximately a week after the home had received an oil delivery.

The home, being sold as part of an estate, had been unoccupied for an unknown period of time. At the time of the home inspection this home was 64 years old.

The inspector wrote (2017/12/09):

Here are photos I took today - this home has a leaky buried oil tank. The sump pit was filled with home heating oil and, remarkably, the fireplace clean out opening was also filled with oil.

The home is part of an estate. The estate executor came for the inspection. Oil was delivered to the home last week.

Thanks to these photographs and information from the inspector we have an opportunity to learn about a severe oil tank leak into a building.

Our photograph above shows the heating oil storage tank fill pipe, feeding an underground storage tank of undetermined size, possibly 550 gallons.

In the oil filler photo above there is one possible clue presaging trouble.

No oil tank vent pipe is visible. Perhaps there is a vent line and opening nearby but out of the range of this photograph.

Watch out: if a heating oil storage tank is not properly vented there is a good chance that it can be burst or leak during an oil delivery. See OIL FILL & VENT PIPING for details.

Oil storage tanks are normally filled rapidly (about 50 gallons per minute) and at pressure.

Normally a heating oil delivery driver will not deliver oil to a tank that she or he suspects is un-sound.

Severe leakage of home heating oil into the basement of a Pennsylvania  home (C)  and  ASHI inspector Lawrence Transue Dec 2017But in this case we speculate that no one knew the condition of the tank, nor had leaks been reported to the oil company. Details are at OIL TANK PRESSURE.

In our second oil spill photo from the same home we see heating oil puddled on the basement floor. Notice also that oil has wicked up into the bottom of wood paneling (red arrows).

Watch out: also - estate managers handling an unoccupied home in freezing climates will want to have the home inspected regularly to protect it from costly damage from loss of heat or plumbing leaks.

A home buyer purchasing a home with an oil storage tank of unknown condition needs to have the tank inspected and probably tested.

A leaky oil storage tank must be emptied and the spill cleaned-up - usually a costly procedure.

It is also possible that there is a bit of subsidence over the oil tank.

If so, that also might be a warning sign of a pending tank collapse, especially at an older property.

Watch out: cleaning up spilled oil from a basement floor can be troublesome but it's most-often feasible.

Below is indicator that this property may be facing such a cost: the sump pit is filled with heating oil.

Heating oil filling the sump pit of this home after an oil tank underground leak (C)  and  ASHI inspector Lawrence Transue Dec 2017

If heating oil has entered this sump pit, apparently by flowing under the building foundation, footings, and floor slab, then this leak is going to be very costly to remediate. State regulations might require removal of the floor slab in order to remove oil-contaminated soil.

Below is another indication that heating oil may have passed under the foundation and floor slab of this home: opening the chimney cleanout at floor level the inspector found that the well in the chimney base was filled with heating oil.

Heating oil spilling out of a chimney base cleanout into the home basement after a severe oil tank leak shortly after an oil delivery (C)  and  ASHI inspector Lawrence Transue Dec 2017

In the photograph our right-pointing arrow suggests that so much oil entered the chimney base that it has overflowed onto the interior floor. (Based on the other photographs of this oil spill shown above, we don't think the oil moved in the opposite direction: across the floor and into the chimney base.)

Watch out: Oil storage tank leaks must be reported under the laws of almost every U.S. state. Regulations concerning oil tank leak reporting, abandonment, cleanup, are at OIL TANK LEAK REPORTING REGULATIONS - ALL

Could this leaky oil tank have been discovered before this catastrophic in-home oil spill?

Maybe. Or as Mark Cramer, Tampa home inspector says "... it depends." When a home is unoccupied for a long time there is a greater chance trouble develops before anyone notices it.

I've seen water leaks from roof and surface runoff that enter a chimney base from outside. I've also seen leaks into a basement from water collecting in the excavation made to install the buried oil tank.

So it' s not a complete surprise to see this significant oil leak showing up from a badly-leaking UST whose oil seeps under the foundation,under the basement slab, into a sump pit, and also into the chimney cleanout and base.

One can but wonder how long the tank was leaking before it was, perhaps, broken open during the last oil fill (if that's what happened).

Lawrence Transue is a Pennsylvania building scientist and consultant, a certified ASHI home inspector, a Licensed Pesticide Applicator, a BPI Building Analyst & Envelope Professional, with 18 Years of Home Inspection Experience. He can be reached by Telephone: 610.417.0763, by Email: as well as at his WEBSITE and at FACEBOOK

Oil Tank Inspection Report Language: Standard, Concise "Buried Tank" Home Inspection Report Language for Buried Oil Tanks

Even if we are told that a tank has been "removed" or "abandoned" we need to review the documentation to gain confidence that the tank abandonment in place or tank removal were done properly and that proper inspections and (where appropriate) tests were performed to assure that the site is not contaminated.

Ultimate cleanup costs where buried oil tank leaks were discovered at properties we have examined have varied between $8,000. and $675,000. in site cleanup costs. We issue a warning to the property buyer or owner. This warning has led to further site investigation, tank testing, and savings in avoiding costly surprises for our clients.

A buried fuel tank [heating oil storage tank] [LP gas storage tank] [unknown type of fuel storage tank] is [was, or appears to have been] installed at this property. Such components are not inspected during a home or building inspection unless specific prior test arrangements have been made for advice by an appropriate expert. Some general advice is below.

[For clients in New York, you should call the US Department of Environmental Conservation (DEC) for advice in this matter. The Southern New York area office is in New Paltz, NY, at 914-255-5453. For clients in other states or provinces, call your local department of environmental protection for advice.]

Watch out: old buried fuel storage tanks at a property may be of un-known use, un-known fuel, un-known condition, and they may be quite dangerous. Hazards include sudden collapse (someone walking over the tank could be injured), and even explosion.

Two workers died when a backyard fuel tank exploded in Westchester County, New York in 2015. Initial reports indicated that the type of fuel storage tank was un-known, possibly oil, LP gas, or liquid gasoline. On 7 May 2015, two workers who were removing the tank, located in Hastings-on-Hudson, were killed as the tank exploded and flew 75 feet through the air.

An environmental consultant cited in a New York Times report posed that the tank probably contained gasoline and that explosive fumes may have been ignited by a spark from a hand-tool or by static electricity during the tank removal. - The New York Times, 8 may 2015 cited at REFERENCES.

Test The Oil Storage Tank: Basic Advice about Testing Buried Oil Tanks

Hire an expert to find hidden or buried tanks, abandoned tanks, or to test existing tanks: Specialty companies and some oil companies have equipment to test buried tanks for leaks. Tanks and soil around and below tanks are tested for evidence of leakage using:

Common oil tank leak tests listed below can tell you if a tank has already leaked and can help assess the chances of an upcoming oil tank leak. The tests are listed here and are discussed in more detail in the document at "More Reading" below.

I advise home buyers to have a soil test performed rather than a pressure test of an existing oil tank, since even if the tank is not currently leaking we would prefer an assurance that it didn't leak before, say from a plumbing connection that was repaired.

OIL TANK LEAK TEST METHODS discusses oil tank testing options and procedures in more detail.

Oil Storage Tank Failure Mechanisms: a Summary of Fuel or Heating Oil Storage Tank Failure Mechanisms and Tank Leak Rates

A basic understanding of why oil tanks leak can help you assess the chances that a given tank at a property has already leaked or is likely to leak soon.

Oil tanks can fail and produce costly oil leaks for more reasons than you might think. Water in the tank, not external rust, is the most common culprit.

But other leak causes include mechanical damage that gouges a tank while it's being buried, oil fill, vent, or supply piping errors that leak oil, corrosive soil conditions, manufacturing defects, weather conditions contributing to in-tank condensation, and delivery of bad oil that is contaminated with water.

OIL TANK FAILURE CAUSES - "Oil Tank Leaks or Oil Tank Failure Causes - oil tank leaks are caused by corrosion, damage, soil conditions, other factors". This document discusses the causes of above ground and underground oil tank leaks in detail.

Oil Tank Failure Rates

If an underground oil tank at a property is 15-20 years old the chances of a leak are high and you need to have the tank tested.

Even if the tank is not leaking now and has not already leaked, if there is an old, buried steel tank at a property you should plan on replacing it before it leaks not afterwards.

OIL TANK FAILURE DATA - Oil Tank Failure Rates - Oil Tank Leak Probability as a Function of Tank Age, Location, Condition, Soil Conditions and Other Factors. This document describes rate or frequency of oil tank leaks or oil storage tank failures, focused on underground storage tanks or USTs.

Oil Storage Tank Removal or Abandonment: Summary of Tank Removal or Abandonment

Oil Tank still OK: Even if a buried oil tank at a property is shown not to have leaked and even if it's less than 10 years old, if the tank is not a special lower-risk unit (fiberglass, plastic, or multi-wall) I advise clients to plan to abandon the tank before it has leaked, substituting a near term big expense for a later term major expense.

Oil Tank Leak Insurance: Oil tank leak insurance has been offered by some oil companies but you'll find them unlikely to write a policy at all on an older high-risk installation.

Oil Tank No Longer in Use If a fuel storage tank is not to be used, for example if you've converted to another fuel, oil tank removal or oil storage tank "abandonment" can involve significant expense.

"Oil Tank Removal" means just that, the tank is excavated, emptied, cleaned, and removed from the property - leaving a large hole to be filled-in.

"Oil Tank Abandonment" means that a tank is left in place, cut open, emptied, cleaned, has its piping removed, and usually filled-in with an approved filler. A proper abandonment procedure involves pumping out remaining fuel, confirming that there has been no leakage, and filling the tank with an approved filler, or removing it entirely.

Typical tank fillers include sand or special foam products to avoid future use or future collapse. These measures, if required, will involve significant expense.

The Oil Tank Leaked: If a tank has leaked the leak must be reported (in most jurisdictions) even if was a small leak, and the tank needs to be removed. Any oil-contaminated soil must be removed as well and taken to an approved waste site.


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