Heating Oil Underground & Above ground Oil Storage Tank Life Expectancy

  • OIL TANK LIFE - CONTENTS: life expectancy of oil storage tanks, both Buried Oil Tank Life Expectancy of Underground Oil Tanks - USTs and Underground Outdoor Oil Storage Tanks (USTs) and Life Expectancy Factors. How long should an oil storage tank last & what are the main factors that affect oil storage tank life & leak risk?Above Ground Outdoor Oil Storage Tanks (ASTs) Life Expectancy - Residential indoors or outside. Above Ground Outdoor Oil Storage Tanks (ASTs) and Life Expectancy FactorsIndoor Above Ground Oil Storage Tank Life Expectancy Factors. Outdoor Above Ground Oil Storage Tank Life Expectancy Factors
  • POST a QUESTION or READ FAQs about typical oil storage tank life and factors that affect oil tank durability and leak risk

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Heating oil storage tank life expectancy:

How long do above ground or buried oil tanks last: oil storage tank life expectancy. This article provides estimates of oil storage tank life for buried oil tanks and above ground oil storage tanks.

We list the factors that affect oil tank life for buried oil tanks and different factors that impact the life of above ground oil storage tanks. How long an oil storage tank can be expected to reliably contain its oil and not to leak depends on quite a few variables, all of which we describe here.

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Buried Oil Tank Life Expectancy of Underground Oil Tanks - USTs

Photograph of - is this heating oil running across the basement floor? Notice the abandoned oil line at the furnace?This article discusses the typical life of USTs followed by a discussion of AST life.

Some things that can shorten the life of an oil tank can be avoided or corrected. The photo shows how a leak develops and appears in an indoor oil storage tank, forming a stalactite of oil and sludge hanging from the bottom of the tank.

Because an oil tank often rusts through from the inside out, the exterior of an oil tank may look fine but in fact it could be paper thin and easily punctured, even by a finger!

The life expectancy of oil tanks is helpful in planning for storage tank testing and storage tank replacement. This is a chapter of our "Heating Oil Underground & Above ground Oil Storage Tank Leaks, Testing, Problems & Solutions, Home Buyer's / Home Owner's Guide" which offers extensive free un-biased oil storage tank inspection and testing advice for property buyers and owners.

While we've found them lasting longer, a common life expectancy of buried oil tanks is 10-15 years. At about 20 years, the risk of leaks from buried steel oil tanks becomes significant. Leaks can occur earlier if a tank was damaged at installation or was not properly piped.

Even if you think the tank is ok, young, and not leaking, buried oil tanks, should be tested for water in the tank bottom. Water should be pumped out since it corrodes the tank and leads to leaks. Oil tank leaks can also be due to damage at time of installation, improper installation, corrosive soils, or piping defects. If the tank is to remain in use, ask your fuel supplier about using an additive or other methods to help remove water.

Life Expectancy of Buried Oil Storage Tanks - Residential

Buried oil tank schematic Carson Dunlop AssociatesIn New England for a two year period [1984-5] among customers who had buried heating oil tanks (16% of total customers) surveyors found an average of 1.7 tank leaks per thousand customers.

They also found 2.5 fuel line leaks per 1000 customers.[4] This finding that twice as many heating oil system leaks occurred in the fuel piping is consistent with the Maryland study reported below.

A 1986 Maryland study found a 40% leak rate in petroleum product storage tanks (oil, gas, kerosene, waste oil) of which oil piping caused 82% of all leaks, and location (urban vs rural) and soil conditions were important factors in leak occurrence.[3]

We do not have similar data for buried gas tanks in residential application.

Also see OIL TANK LEAKS & SMELLS. Sketch of a buried heating oil tank installation is provided courtesy of Carson Dunlop Associates.

Underground Outdoor Oil Storage Tanks (USTs) and Life Expectancy Factors

Photograph of an oil tank filler pipe placed at grade level.
  • Exposure of the oil tank filler to water entry or surface runoff (as shown in the photograph): some oil tank installers or homeowners insist on installing the tank filler flush with or even below ground level, perhaps for aesthetic reasons. This detail increases the risk of snow melt or surface runoff entering the oil storage tank, particularly if the filler cap is left off or if its o-ring or gasket seal is not perfect.
  • Wrong tank type for buried use: smaller oil tanks which have been buried, such as a 250g or 275g tank, especially if more than 10 years old, are suspect: we have not ever found one of these that was labeled as approved for outdoor below-ground use. If you have a buried oil tank in this size range further investigation is warranted.
  • Mechanical damage to the tank during installation, such as scraping its protective coating (if there was one), or omission of any protective coating on the buried tank. Damage might occur for example, by scraping the tank with equipment used to move it, or by setting the tank into a hole atop a rock or other debris. Fiberglass or plastic tanks may be more vulnerable to serious mechanical damage during installation.
  • Mechanical damage to buried oil tanks & tank piping due to vehicle traffic passing over or near the tank, causing movement, flexing soils or flexing tank and piping
  • Damage to oil storage tank when fill & vent piping are struck by vehicles outside, causing bends or cracks where those pipes connect to the top of the oil storage tank (this can happen to both buried and above ground oil tanks)
  • Corrosive soils - soil corrosivity may be a significant factor in buried steel oil tank life in areas of soils with a high corrosivity index. Plastic or fiberglass tanks are less likely to be affected by soil corrosivity. But oil tank piping and piping connections will be impacted by soil corrosion and are a principal source of leaks. Burying copper or brass oil tank piping & fittings touching or in close proximity to other buried pipes such as a galvanized iron water pipe can also cause corrosion.[3]
  • Conductive soils - clay soils that are more conductive than sandy soils increase the exposure of the buried oil storage tank to electrical currents, especially in urban areas or where there are electrical grounding or wiring faults. Electrical current exposure can increase oil tank corrosion and can exacerbate galvanic corrosion already going on. [3]
  • Amount of ground water in soil: wet soils increase the risk of corrosion on buried steel tanks and increase the risk of leaks into a damaged (or poorly plumbed) tank for both steel and plastic/fiberglass oil storage tanks.
  • Defective oil storage tank welds

Life Expectancy of Above Ground Oil Storage Tanks - indoors or outside

Duplex AST oil tank installation (C) D FriedmanWe suspect that there is a wide variation in indoor above ground and outdoor above ground oil tank life due to the considerable variation in both the quality and thickness of oil tank steel (older tanks seem to have been a heavier gauge steel), as well as other factors in oil storage tank life.

We have seen indoor oil tanks easily in good condition that are 60 years old or older, and we have found failures in newer oil storage tanks that may have been made of thinner or cheaper steel and that did not last as long as the original ones.

Rather than guess at oil tank condition, we suggest that if your home has an older above ground oil storage tank, ten years old or older, you should

  • Inspect heating oil fill & vent piping & oil distribution piping with great care - most oil tank system leaks appear to occur at piping connections.[3] Details are
  • Inspect the oil storage tanks themselves. Make a simple visual inspection of the oil tanks and piping for leaks; light external rust is not usually a problem - oil tanks usually corrode and leak from the inside, and usually in the bottom 1/4 of the tank; See these articles:
Photograph of an above ground oil tank with minor leaks. Photograph of an above ground oil tank which may be in serious trouble.
  • If the oil tank is leaking, such in the photographs above, don't ignore it. The first tank shown here (above left) has seepage at its fill and vent fittings, a rather typical and trivial problem which is hard to avoid unless meticulous sealant application is used during assembly of the fill and vent piping - the machining at the tank top and on larger diameter piping is often a bit rough.

    The second tank (above right) is an older oil tank which shows the same seepage around the tank top fittings.
    But what about those oil stains on the lower left tank body? The tank may be leaking at its seams or from perforations. Further investigation is warranted.
    See Leaky Heating Oil Tanks - Advice for Home Owners or Buyers: causes of leaks in oil tanks, oil tank testing alternatives, what to do about leaky tanks: D. J. Friedman, ASHI Tech. Journal, Vol.2 No.1, Winter, 1992 p. 42-43 Illus
  • Have the oil tank steel tested for soundness -
    See OIL TANK LEAK TEST METHODS - if the tank is not sound, have it replaced.
  • If there is evidence of water or sludge in the oil tank, ask your oil company to pump out sludge or water;
  • If heating oil tank sludge has been clogging the heating equipment oil filters, double the oil filter size and quantity (install two filters in parallel) so that you can get from one annual heat service call to the next without a no-heat call due to clogged oil filter. If sludge has clogged oil piping lines it may be possible to clean them but replacement is often necessary.
  • If you have to install a new oil tank and there is not room to place a tank indoors, we recommend building a cover over the oil tank to protect it from weather and to permit heating the tank enclosure just enough to keep it above 35 degF.

    We prefer to avoid outdoor tanks because of the risk loss of heat due to water, ice, or fuel waxing, OR because the owner has to pay more for heat by having to burn kerosene mix or add pour point depressants at each oil fill-up)
    if you have to to to an outdoor tank, enclose it and give it a little heat is the best installation.

Thanks to reader Robert Frank for suggesting a discussion of indoor oil storage tank life.

Above Ground Oil Storage Tanks (ASTs) and Life Expectancy Factors

Indoor Above Ground Oil Storage Tank Life Expectancy Factors

Indoor oil storage tank leak points (C) Carson Dunlop AssociatesWe discuss the inspection of above ground oil storage tanks in detail at ABOVE GROUND OIL TANK (AST) GUIDE.

Sketch at left of leak points at an indoor oil storage tank is provided courtesy of Carson Dunlop Associates.

Here are trouble signs for ASTs:

  • Visible oil seepage (see the seepage and leak notes discussed above at indoor oil tanks)
  • Water accumulating inside the oil storage tank from bad oil deliveries or from wide temperature swings and in-tank condensation. Test the tank for water and remove water from the oil tank by pumping (large amounts) or by absorbing chemicals or pads (small amounts of water).
  • Poorly-made or corroded or damaged plumbing connections or oil piping. Inspect and correct any leaky fittings. Look for under-sized vent piping or both fill and vent piping that are smaller than 2" in nominal diameter.
  • Defective oil storage tank welds
  • Mechanical damage to oil storage tank fill & vent piping or to the oil tank where such piping connects, such as being struck by vehicles outside, causing bends or cracks where those pipes connect to the top of the oil storage tank (this can happen to both buried and above ground oil tanks)

Outdoor Above-ground Oil Storage Tank (AST) Life include the following:

Above ground oil tank outside (C) D Friedman
  • Exposure of the oil storage tank to wider temperature swings, especially in cold and humid climates can increase in-tank condensation
  • Exposure of the tank filler or vent pipes to rain, especially to roof runoff for tanks mounted under the eaves of a home and especially if a proper cap is not kept on the tank filler pipe or if the vent pipe is not properly installed and shielded.
  • External oil tank rust due to exposure to the weather. Many small tanks, 250g or 275g, were never rated for outdoor use, as you may easily ready by examining the embossed UL label affixed to most tanks.

    Manufacturers of newer oil storage tanks in this size range appear to have removed this "indoor use only" wording from the UL label, as you can see in the photo shown here. We have not learned whether the standard was changed, the tanks were changed, or simply the label was changed. An outdoor tank should be protected from the weather and in freezing climates should be given shelter and warmth.
  • Improper oil tank installation / installation of improper oil tank type: two AST oil tank photos above shows an old, indoor-oil tank which was moved outside and placed onto the soil surface below a deck, and then was half buried. What is this tank, a buried tank or an above ground tank? It was not rated for outdoor use at all and is at extra risk of leakage due to placement of the tank body directly in contact with the soil.
  • Improper oil storage tank supports, such as failure to keep the outdoor tank off of the ground, to install it at the proper pitch and direction of pitch, and to install it on level, secure piers can lead to a tank tipping over, ripping open an oil line, and obvious catastrophes of oil spillage and heat loss.
Photograph of a modern oil storage tank listing label. Photograph of a half buried outdoor oil storage tank.

Questions or comments about Heating Oil Storage Tank Life

Questions & answers or comments about typical oil storage tank life and factors that affect oil tank durability and leak risk

Question: I've seen claims that oil storage tanks last even up to 40 years - who's right?

Oil tank float up (C) D Friedman

I refer to one of your article on your website (above on this page), which I am curious and very much want to know more. Are there justification to that?

Or it depends on other parameters such as weather and soil conditions? Some websites mentioned that such tank can last even up to 40 years. - M.A., PUB, Singapore National Water Agency

Our InspectAPedia photo of an abandoned "buried" oil tank shown at left is an example of a buried oil storage tank that had a very long and leakproof life - until it was abandoned, forgotten, and left empty. Worse the tank had been buried alongside a waterway - a stream in Rhinebeck, NY.

This oil tank was subjected to very wet soil conditions over several decades, apparently without leaking oil into the environment. But we can't promise the same performance for all buried tanks. It depends ...

Reply: how long do buried oil tanks last ? ... It depends

Underground oil tank being transported (C) D FriedmanThankyou for the interesting oil tank life question. A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem or factors that might affect the life of a specific oil tank when at a specific site or oil tank, even before any actual tests for evidence of oil tank leakage. That said, here are some things to consider:

  • The data we reported above on oil tank leak rates was based on industry surveys of oil tank age and leak report rates in an area of the U.S. where natural gas is not readily available, where oil heat is most commonly used, and therefore where there was a large population of oil storage tanks.

    I agree completely that in certain other environments (cited below) an oil tank may have a longer life than in the north eastern area of the United States.
  • The actual life of an oil tank in ground is widely affected by local conditions: soil acidity, water levels, even a scrape or damage during installation. I photographed the oil tank in the back of the delivery truck (above left) as it was being transported - the tank rolled and smashed from side-to-side during its trip to the jobsite. That banging around could easily have damaged an anti-corrosion protective coating on the tank. Worse, an "indoor-use-rated" oil tank that is installed outdoors, especially buried, is likely be of thinner steel and lack a protective coating against soil moisture and corrosive agents.
  • An area of wet soils or soils with other than a neutral pH are more of a challenge to oil tank life as are soils that are more conductive (clays, for example) where in urban areas there may be stray electrical currents adding to corrosive factors for the oil tank or its piping fittings.
  • The age or generation, and date of manufacture of oil storage tanks can in at least some cases affect the probable durability of the tank. Oil storage tanks produced several decades ago may have used thicker steel than modern tanks; certainly I've personally observed newer above-ground storage tanks that are made of steel that I could dent with my hand - not something I could (nor would try to) do at oil tanks I've inspected dating from the 1960 and 1970's.
  • The oil tank life is also affected by what's put into it - oil deliveries containing water, for example, will certainly shorten the tank life. Some conditions that increase the chances of receiving water along with oil during a heating oil or fuel oil delivery including what's going on at the oil storage depot.
    • Oil delivery trucks are typically filled from a large oil storage depot tank, often by a river or railroad (via which oil is delivered). Oil storage depots may deliberately keep some water in the bottom of those large storage tanks so that if a tank starts to leak the leak is discovered early - in the form of less-polluting water. But if the depot tank is near-empty OR if the tank happens to be receiving a shipment of oil being pumped into itself at the same time that the oil delivery truck is obtaining a fill-up, the truck may pick up some water mixed into its own tank.
  • So in the U.S. in Arizona and the dry Southwest, in Central Mexico, Saudi Arabia, or some areas of mainland China where soils are very dry, an oil tank buried in dry ground could certainly have a much longer life than the same tank buried in New England in the U.S.

If you have reason to need an oil storage tank that is resistant to corrosion damage, take a look at some of the fiberglass and other plastic alternatives as well as (more costly) multi-walled oil storage tanks that are required in some jurisdictions and applications.

What is the Legal Definition of "... up to xxx..." Claims in Advertising?

Watch out: about "up to" claims.

Finally, whenever you see someone claiming "... up to ..." you don't really know what to make of such remarks. "Average life of an oil storage tank" is nothing like "... up to... " life. "Up to" after all, could include one single instance of an oil storage tank that was reported to be 40 or 60 or some other age. And meaningless.

Consulting with an advertising attorney in 2010 we learned that there is a legal definition of "up to" claims - at least in advertising case law. You can claim "up to" for a product if 10 percent of the product meets that standard. So if one oil tank lasted for 40 years somewhere but another nine in the same test set all failed in the first month of service (certainly not really likely), the tank "expert" could still claim that his oil tank installations lasted "up to 40 years".

I appreciate the question and welcome reports of oil tank life from folks in other countries and environments. We are dedicated to making our information as accurate, complete, useful, and unbiased as possible: we very much welcome critique, questions, or content suggestions for our web articles. Working together and exchanging information makes us better informed than any individual can be working alone.

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information for the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website.



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