Leaky Heating Oil Tanks - How Oil Tanks are Tested for Evidence Leaks, of Current or Previous Oil Spills
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Oil tank leak testing guide: this document describes the common methods used to test oil storage tanks for evidence of
leakage, either by soil testing, pressure testing of the tank, or by other tank screening measurements.
Leaking oil tanks are not only a concern as contaminants of the water supply, but
have become an increasing general
environmental concern addressed by the DEC. Leaking commercial equipment and
even simply-suspect equipment have been extremely costly to address. Such
burdens were never anticipated when the equipment was installed. While similar
regulations pertaining to residential installations are scarce, this topic is
of growing concern to home owners and home
buyers. Other steps to locate and test heating oil storage tanks at properties, both buried tanks and above ground tanks
are discussed at other documents at this website. Readers should also see OIL TANK LEAK ADVICE and OIL TANK LEAK CAUSES.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
OIL TANK LEAK TESTING - How Oil Tanks are Tested for Evidence of Leakage
Specialists and some oil companies have equipment to test buried tanks for
leaks. Both simple pressure-testing and sophisticated electronic testing are
used, mostly on commercial equipment, and more recently on residential tanks.
Testing for water in the tank is simple and can be done by any service person
using a simple chemical paste on a probe. A lot of water in the tank is a reason
to be pessimistic about its condition.
There are a number of tank testing methods currently in use, varying in risk to
the tank, cost, invasiveness, length of time to complete, and some, requiring
shutting down of the heating system during test period. See "How do you
choose the right tank testing method?" Cynthia Johnson, Fuel Oil & Oil
Heat Magazine, November 1995.
- Low-psi oil tank pressure-testing for leaks is used to test a tank for existing leaks.
- Soil testing for oil tank leaks looks for evidence of actual oil contamination in the soil. A proper soil
test is based on having located the buried tank or the site where a tank was buried, and taking
borings to a depth approximately just below the tank bottom.
- Electronic testing of oil tanks to check for leak scan also screen tanks for evidence of damage - usually this was used only on commercial jobs. Also see Mesa 2-D TEST for OIL TANK LEAKS.
- Oil tank ultrasound screening program (photo above) is offered by some oil companies who scan the bottom section of above ground oil tanks to measure the thickness of the tank steel. Tanks that pass an ultrasound screening test may be insured against future leakage.
We discuss ultrasound screening of oil tanks at
ULTRASOUND TEST for AST OIL TANKS
- Water testing in oil tanks can indicate the risk of in-tank corrosion and thus leakage - an easy first-pass which
can be used at both above ground tanks and buried oil tanks. See WATER in OIL TANKS, TEST FOR.
- Ground scanning radar or magnetic sensing is also used to locate buried steel tanks.
OIL TANK LEAK TEST: Mesa 2-D Digital Nonvolumetric Oil Tank Tightness Test
This test for oil tank tightness developed by Mesa Engineering, uses a digital probe and using ultrasound, examines frequency changes to detect a leak in the oil tank or its piping.
The Mesa 2-D Digital test includes a "U-L" frequency leak test that detects leaks in the oil tank or its piping. The Mesa 2-D test also detects vapor bubbling ("P-L" frequency leak) indicating that the oil storage tank or its piping contains a leak in the oil piping or oil filler piping portion of the system.
This is a low "negative pressure" or vacuum test using a vacuum of 60 inches of water or –2.16 psig. The manufacturer requires that test operators be certified at least every two years.
According to the developer, Mesa Engineering, a U-L frequency leak typically occurs in the oil vent pipe or fill pipe, and can often be repaired, while a P-L frequency leak usually indicates a critical system failure that means the tank will probably be taken out of service and abandoned.
Watch out: In reader correspondence we have a report of an owner's concern about an apparent "coincidence" that within two weeks following a Mesa 2-D oil tank test a catastrophic oil tank leak was found and a costly cleanup followed. Not only is the Mesa 2-D oil tank test considered "safe" (it does not expose the oil tank to high pressure or high vacuum), but a review of the Mesa 2-D tank test report for this case disclosed that the test itself detected a tank failure.
Our OPINION was that provided the test was conducted properly, the most likely explanation of the apparent coincidence was that the test had correctly detected an oil tank leak that was not previously recognized, and that had existed for a considerable time.
Mesa 2-D Oil Tank Test Report Example #1 - see this example of a Mesa 2-D oil tank leak test that found significant evidence of an oil tank leak. The owners reported that within two weeks a major oil leak was confirmed and a cost underground oil tank replacement and oil spill cleanup was required. The company who conducted this test, ATS Environmental Services Co., includes in their Mesa 2-D test description
MESA 2-D test results are 100% digital & computer analyzed which eliminates the chances of human error affecting test results. Many other tank test systems are analog and not computer controlled. These inferior test methods rely heavily on the testing technician listening for leaks or bubbles in the tank bottom. The MESA 2-D uses computer and digital acoustic profiling technology to evaluate the integrity of underground tank systems. The MESA 2-D test system will not damage the tank or heating system. This is not an air pressure test! MESA 2-D test system can test tanks with any level of fuel including tank that are empty.
Mesa Oil Tank Test Report Example #2 - this example of a MESA oil tank test also found that the tank was leaking. As we pointed out to the reader who contributed this oil tank test report, the test found a tank leak, called for appropriate repair action, and did not (indeed could not) indicate the extent of soil contamination that may be present.
Interpreting a MESA 2-D oil tank test report
In the example MESA 2-D oil tank leak test Mesa Oil Tank Test Report Example #2 the test company recommended that possibly leaking oil piping be inspected and repaired if found faulty (though it appears that the technician didn't think that was the problem. The company continues to indicate that if piping repairs do not stop the leak, the tank will need to be abandoned according to proper procedures.
OPINION-DF: even if the oil piping is repaired and the repairperson believes that a leak was fixed, there is a potential for significant increases in the later cost to abandon the oil tank if in fact it continues to leak, and because there can be multiple leak defects in any tank and piping system (so that fixing one may not fix them all). For that reason, a follow-up test might be appropriate.
Mesa 2-D Method with ACT v1 Water Level Sensor - test description and specifications from Mesa Engineering - web search 6/22/2010. Mesa Engineering, 5801 Dierker, Houston TX 77041 713-895-7000, [company website link in this literature is not functional]
OIL TANK LEAK TEST: PRESSURE TESTING - Oil Tank Pressure Testing Advice
Using this tank testing method the oil tank is sealed and pressurized to a low psi level, then
carefully monitored for a pressure drop, perhaps for 24 hours. This method is comparatively
quick to execute but I don't care for it. Notice (in our photo at left) that some oil tank manufacturers do not want their oil tanks pressure-tested after the tank has been installed. Details are at OIL TANK PRESSURE.
- First, if there is a pressure drop, additional testing
will be required to determine if there has been actual oil seepage into the soil. (A leak could have been
a minor one at the tank top, for example.) The additional testing is pretty-much the same as
my second method described below, so the consumer ends up paying for testing twice in this case.
- Second, even if there is not a pressure drop, I'm not sure that there hasn't been a tank
leak in the past, perhaps fixed by a plumbing repair or other method.
Some home owners balk at this test, fearing that the pressure of the test procedure will "burst" an oil
tank that is about to fail. I am doubtful that this is a legitimate concern. The pressure at which the tank
is being tested is almost certainly a much lower psi than the pressure to which the tank is subjected
while it is being filled by the oil delivery truck and driver.
OIL TANK LEAK TEST: SOIL TESTING - Soil Tests for evidence of tank leakage
We prefer this method for testing for evidence of leaks at buried oil tanks. The cost for soil testing is about the same
as the first method where buried tanks are installed.
Multiple soil borings are collected around the tank, at a depth just past the
level of the tank bottom. The soil samples are tested for petroleum product contamination.
This is
considered the definitive test for oil tank leakage, and if the tank has not leaked, it provides more reliable documentation of
that fact. More time is needed to complete the test as there is a delay for the lab work.
Consider that if you opted for the tank pressure test described earlier, and if the test showed that the tank
has leaked oil into its surrounding soil, some additional testing is going to be needed to confirm the extent of
soil contamination. It seems to me it's better to test the soil in the first place, thus also covering not only current but past conditions.
Finally, if we are told that an oil tank has been "remove" or "abandoned" at a property, we expect to be given the
documentation that outlines who did what when, and importantly, what steps were taken to assure that there was no oil leak that was
simply left for the next owner to discover and clean-up. If adequate documentation is not provided, a soil test is certainly appropriate. One
of my clients took this advice and discovered, and avoided having to pay for, a $60,000. site cleanup at the property he was buying.
OIL TANK LEAK TEST: TEST FOR WATER - Test oil tanks for presence of water
See OIL TANK WATER CONTAMINATION for detailed advice on how to remove water from oil storage tanks. Excerpts are below.
Buried tanks, such as heating oil tanks, should be tested for amount of water
present in tank bottom, and water should be pumped out. Even above-ground tanks can take on large amounts of water from roof spillage, condensation, or a bad oil delivery. (Photo at left).
In fact, water can
accumulate in indoor or outdoor above ground oil storage tanks too, either from exposure to varying
temperatures (in-tank condensation) or from the occasional
delivery of bad oil which contains excessive water content.
A neat way to look for a history of water in the heating oil storage tank is to check the
oil filter canister itself. Many oil burners are protected by a heating oil filter
installed either at the tank or at the oil burner. (Every heating boiler burning oil
should have one of these filters installed to protect the equipment.)
If the oil tank has a high level of water, especially if the oil lines run to the oil burner from
the bottom of the oil tank, some of that water will have been making its way to
the oil burner where, en route, it is (usually) trapped in the oil filter. If you open an oil
filter container and see that its metal parts are rusted, or that there is a lot of rusty sludge
in the bottom of the filter holding canister, the oil tank needs to be checked further for water
The oil service technician can check the level of water in an oil tank by putting some "oil finder paste" on the
bottom of a stick or probe which is inserted into the tank and to its bottom. The paste changes color in the presence
of water, showing, by the length of color change on the probe, the depth of water in the bottom of the tank. Obviously this
trick is much easier if the tank is outside than indoors where a basement ceiling can make probing the oil tank difficult.
Ask your oil service company to perform this test.
Alternatively, if an underground oil storage tank also needs an oil tank tightness test or oil tank leak test, the Mesa 2-D TEST for OIL TANK LEAKS can also detect water leakage into the tank.
While we've found them
lasting longer, a common life expectancy of buried oil tanks is 10-15 years. We
do not have the same data for gas tanks. Life may be similar.
If the tank is to
remain in use, ask your fuel supplier about using an additive
or other methods to help remove water. Warning: on some older oil tanks which had a lot
of sludge in the tank, as the de-watering additive (such as "4-in-1-HOT (TM)") was added to the
tank we found an increase in the debris making its way to the heating oil filter. You should inspect
the filter cartridge for water and debris and have it changed more frequently until this question
is closed. It's more trouble but the end result is a more reliable oil storage tank and heating system.
See OIL TANK WATER CONTAMINATION for detailed advice on how to remove water from oil storage tanks.
OIL TANK LEAK TEST: Ultrasound testing of above ground oil tanks for tank leak risk
Oil tank ultrasound screening program (photo above) is offered by some oil companies who scan the bottom section of above ground oil tanks to measure the thickness of the tank steel. Tanks that pass an ultrasound screening test may be insured against future leakage.
The oil company technician uses an ultrasound scanner to make twelve thickness measurements on the lower portion of the oil tank and records the thickness at each location. Typical oil tank thickness readings on an older above-ground indoor oil tank may range from 0.105 to 0.185 inches in thickness.
If all 12 sample point thicknesses exceed 0.100" the oil tank "passes" and the dealer offers $1000. insurance for a year as part of the fee. Our photo (above) shows an oil tank sonogram in process for the author, conducted by Nash Brothers Oil Company, Hyde Park, NY
Watch out: observing some above ground oil tank tests using the ultrasound screening program makes us nervous. It is inconvenient for the technician to both observe the instrument readings and then climb out of the position shown in our photo (above) to write down the data.
As a result we have seen tank test technicians "memorize" ten or 20 readings and then write them down by recollection of the "ballpark" figures. This is reasonable in that the technician is really just looking for any readings that cross the threshold of unacceptable tank steel thickness.
But it remains inaccurate and risks oil tank test data errors or skewing by operator error. Further, if the test finds steel thickness readings close to the threshold of acceptability, we recommend that additional "spot checks" be taken of the tank's thickness in that area, rather than simply screening the tank bottom at larger spatial intervals.
See WATER in OIL TANKS for added
suggestions for finding and removing water from oil storage tanks.
OIL TANK TESTING STANDARDS
U.S. & Canadian Standards groups and authorities pertaining to oil or other fuel storage tanks and tank testing include
- ASTM
- ASTM #-1739 - 95 (2002) Standard Guide for Risk-Based Corrective Action Applied at Petroleum Release Sites, quoting from ASTM:
1.1 This is a guide to risk-based corrective action (RBCA), which is a consistent decision-making process for the assessment and response to a petroleum release, based on the protection of human health and the environment. Sites with petroleum release vary greatly in terms of complexity, physical and chemical characteristics, and in the risk that they may pose to human health and the environment. The RBCA process recognizes this diversity, and uses a tiered approach where corrective action activities are tailored to site-specific conditions and risks. While the RBCA process is not limited to a particular class of compounds, this guide emphasizes the application of RBCA to petroleum product releases through the use of the examples. Ecological risk assessment, as discussed in this guide, is a qualitative evaluation of the actual or potential impacts to environmental (nonhuman) receptors. There may be circumstances under which a more detailed ecological risk assessment is necessary (see Ref (1).
1.2 The decision process described in this guide integrates risk and exposure assessment practices, as suggested by the United States Environmental Protection Agency (USEPA), with site assessment activities and remedial measure selection to ensure that the chosen action is protective of human health and the environment. The following general sequence of events is prescribed in RBCA, once the process is triggered by the suspicion or confirmation of petroleum release: ...
- ASTM - www.astm.org
- CSA Standards - Canada
- NFPA
- NFPA 30: Flammable and Combustible Liquids COde (2008)
- NFPA 31: Standard for the Installation of Oil-Burning Equipment (2006)
- NFPA 54: National Fuel Gas Code (2009)
- NFPA 58: Liquefied Petroleum Gas Code (2008)
- NFPA 101: Life Safety Code (2009)
- NFPA 225: Model Manufactured Home Installation Standard
- NFPA 329: Handling Underground Releases of Flammable and Combustible Liquid
- UL & UL-Canada
- Aboveground Tanks, ULC-S601, -S630, ULC/ORD-C142.18, ULC-S653
- Protective Coating for Underground Steel Tanks, ULC-S616, CAN/ULC-S603.1
- Storage Cabinets for Flammable Liquid Containers, ULC/ORD-C1275
- Bulk Containers, Nonmetallic, for Combustible and Non-combustible Liquids {containers-Tanks}, ULC/ORD-C142.14
- Tanks for Used Oil, ULC-S652
- Tanks for Heating and / or Generator Fuels, Aboveground, CAN/ULC-S602
- Underground Tanks, ULC-S615, 603, CAN/ULC-S603.1
- Anode Assemblies, Underground Tank Protection, ULC-S618
- Shop Fabricated Steel Aboveground Tanks For Flammable and Combustible Liquids, CAN/ULC-S601
- Aboveground Steel Tanks for Fuel Oil and Lubricating Oil, CAN/ULC-S602
- Underground Tanks, ULC-S615, Steel Underground Tanks for Flammable and Combustible Liquids, ULC-S615
- External corrosion Protection Systems for Steel Underground Tanks for Flammable and Combustible Liquids, CAN/ULC-S603.1
- Aboveground Steel contained Tank Assemblies for Flammable and Combustible Liquids, CAN/ULC-S653
- Tank Assemblies for the Collection, Storage and Removal of Used Oil, CAN/ULC-S652
- Hose and Hose assemblies for Flammable and Combustible Liquids, CAN/ULC-S612
- Hose Nozzle Valves for Flammable and Combustible Liquids, CAN/ULC-S620
- Non-metallic Underground Piping for Flammable and Combustible Liquids, CAN/ULC-S660
- Double Containment Fibre Reinforced Plastic Linings for Flammable and Combustible Liquid Storage Tanks, ULC/ORD-C58.4
- US EPA
A discussion of methods for finding evidence of previous or current buried tanks
at properties is at BURIED OIL TANKS, FINDING
More detail about the chances that an oil tank is leaking or about to leak is at TANK FAILURE RATES.
More detail about the causes of oil tank leaks, both buried and above ground tanks,
is at OIL TANK FAILURE CAUSES.
Regulations governing tank leak reporting and tank abandonment as well as the registration
of oil tanks at properties is at OIL TANK REGULATIONS
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- ATS Environmental Engineering, Advanced Tank Services Co., 800-440-TANK / 800-440-8265 - http://www.atsenvironmental.com/Mesa.htm - web search 07/24/2010
- Yamada Pumps, 800 990-7867, is a leading producer of
industrial equipment since 1905, and of fluid handling products
for over 60 years. Yamada America supports pump requirements for North, Central, and South America and has an assembly facility in the U.S. in Arlington Heights, IL. Special thanks to David Hollen, Applications & Technical Support, 847 631-9200 ext. 218, for technical consulting regarding pump selection and capacity.
- Boyles Law: this simple gas law explains the relation between pressure and volume when either of those changes - P1 • V1 = P2 • V2 A nice online calculator for Boyles Law simple pressure and volume change operations is provided by 1728 Software Systems and can be found online at www.1728.com/boyle.htm
- "Chapter 2, Operating Your Heating Oil Tank", Main Department of Environmental Protection, maine.gov/dep/rwm/ust/pdf/hotdoc2.pdf and see maine.gov/dep/rwm/ust/ for Maine's basic guide to oil storage tanks and maine.gov/dep/rwm/ust/statutesrules.htm for Maine's UST stautes and rules.
- "Roles of Passivation and Galvanic Effects in Localized CO2 Corrosion of Mild Steel," Jiabin Han, Yang Yang, Srdjan Nesic and Bruce N Brown
Institute for Corrosion and Multiphase Technology,
Department of Chemical and Biomolecular Engineering,
Ohio University
342 West State Street,
Athens, Ohio 45701,
A galvanic mechanism of localized CO2 corrosion was explored to explain a “mesa” type of localized CO2 corrosion. Localized corrosion of mild steel in a deaerated environment dominated by CO2 can be caused by local defects in the corrosion product film/scale covered surface. After the film is locally damaged, the bare surface, usually small in relation to the film covered surrounding area, corrodes one or more orders of magnitude faster than the film protected area. It was found that the open circuit potential (OCP) of the two surfaces is different, a higher OCP at the film covered surface (cathode) and a lower OCP at the bared surface (anode). The OCP difference between the anode and cathode drives the localized corrosion. The causes for this OCP difference between these surfaces were investigated. Studies using potentiodynamic sweeps have shown the passivation of the carbon steel surface, which was developed at higher pH under the FeCO3 film. Cyclic polarization experiments reconfirmed the passivation phenomenon. The nature of the passivation was further explored by a depassivation experiment. The passive film dissolution or depassivation may help detach FeCO3 film from substrate steel bulk and cause it to be removed more easily. These results have been combined into a 2-D galvanic mechanism, which can be used to explain the “mesa” localized CO2 corrosion for mild steel.
Key Words: Localized CO2 corrosion, galvanic mechanism, mesa attack, potentiodynamic, cyclic polarization, self-passivation, depassivation, passivation
- Mesa Engineering, 5801 Dierker, Houston, TX 77041, Tel: (713) 895-7000
E-mail: charlie@atsenvironmental.com,
URL: www.mesatest.com [NOT a functional URL - autoforwards to atsenvironmental.com - Tel: (816) 443-2494
- Nash Brothers Oil Company, located in Hyde Park, NY, (845) 229-8695, offers oil delivery and oil heating services in the New York Hudson Valley area.
- OIL TANK REGULATIONS lists oil tank regulations for all U.S. states and protectorates as well as Federal and some Canadian authorities on oil tank regulation and leak reporting
- "Development Of A Tank Test Method For A National Survey Of Underground Storage Tanks" U.S. EPA - text file at http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=2000ZF9E.txt
- "Review of Effectiveness of Static Tank Testing (UST#50A)", U.S. EPA, Waste oils; Storage tanks; Leak detection; Static tests; Estimating; Leakage; Statistical analysis; Standard error; Standard deviation; Error analysis; Confidence limits; Underground storage;, http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=100006YB.txt
- "Evaluation Of Volumetric Leak Detection Methods For Underground Fuel Storage Tanks Volume 1 {ust #34}", U.S. EPA, http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=2000954I.txt
- "Standard Test Procedures for Evaluating Leak Detection Methods: Nonvolumetric Tank Tightness Testing Methods", U.S. EPA, http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=10001BVL.txt - web search 07/24/2010
- "[Fuel Storage] Tank Corrosion Study", U.S. EPA report on gasoline and oil tank corrosion, James H. Pim, P.E., John M. Searing, Suffolk County DOHS, 15 Horseblock Place, Farmingville Long Island, NY 11728, November 1988, for the Office of Underground Storage Tanks, U.S. EPA. ATTN: David O'Brien. The report presents a study of 500 underground storage tanks spanning 24 February 1987 and September 1 1988 and summarizes earlier reports on this same study. Tank sizes ranged from 175 gallons to 50,000 gallons, and oil tank ages ranged from two years to 70 years old. All 500 oil storage tanks were constructed of welded steel, and 12 other tanks that were other than plain steel were also examined. Summary [with minor edits for clarity by DJF]
The major conclusions [were] summarized as follows:
- Size is more important than age in predicting oil storage tank failures
- In general, small tanks are much more likely to perforate than large tanks due to thinner walls found in smaller oil storage tanks
- Compared to external corrosion, internal corrosion is insignificant [in the underground oil storage tanks examined - warning from DF: the opposite is probably the case regarding above ground storage tanks].
- Fuel oil tanks are just as susceptible to leak perforation as gasoline tanks of the same size
- Existing fuel storage tanks are in worse shape than is demonstrated by storage tank testing
- Storage tanks to not always leak immediately on perforation
- Thanks to reader R.I. for discussing an underground oil tank failure and related tank tests that had been performed - June 2010
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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