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Oil Tank Leaks or Oil Tank Failure Causes - oil tank leaks are caused by corrosion, damage, soil conditions, other factors InspectAPedia®  -     Causes of oil storage tank leaks or other oil tank failures in above ground or buried oil tanks Oil tank leaks that cause heating oil smells & odors, sources of heating oil odors in or at buildings Questions & answers about the causes of oil storage tank leaks

This document explains the common reasons for oil tank leaks in or from home heating oil storage tanks. Both underground tank leaks and above ground storage tank leak causes are discussed. Oil tank leaks are caused by corrosion, mechanical damage, soil conditions, other factors which are explained here.

See OIL TANK LEAK ADVICE for our detailed advice on handling leaky oil tanks as well as links to oil tank leak regulations for U.S. states and Canadian provinces. Readers should also see BOILER NOISE SMOKE ODORS for a discussion of flue gas leaks, smells, and hazards from the combustion products of oil burning heating appliances.

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OIL TANK FAILURE MECHANISMS - Fuel or Heating Oil Storage Tank Leak Failure Mechanisms

Oil tank leaks, depending on the location and size of the leak, can lead to costly environmental contamination and cleanup costs outdoors or indoors in buildings. In addition, oil tank leak smells or fumes from indoor leaks or oil spills are a source of building occupant complaints that need to be addressed.

External oil tank rust, unless very heavy, isn't highly correlated with internal rust, corrosion, and tank leaks. Most oil tank failures are due to rust perforation from the inside of the tank. This means that if you see any indications of even a pinhole or leak on an oil tank, be careful! The steel may be quite thin and can be easily punctured even though from outside it may look pretty good.

OIL TANK RUST PERFORATION - Usual Reasons for Oil Storage Tank Leaks - Rust Perforation

Underground fuel storage tanks usually fail from rust perforation from the inside of the tank, due to several effects of water inside the tank including, in the case of heating oil, combination of water with sulphur in the fuel.

So if a test shows that there is a lot of water in a buried oil tank one would be more pessimistic about its remaining life.

Water in home heating oil joins with sulphur in this case to become acidic and corrosive. It causes tank failure by rust penetration from the inside. Also, there may be a bacteria living in tanks, existing at the water/oil interface, digesting organics and excreting acids.

The corrosiveness of this activity is often most significant at the water-oil interface in the tank, which explains why some tank leaks will develop not at the very bottom of the tank (but look there too) but instead, a few inches up, along the side of the tank.

The height of this corrosion line along the sides of the inside of the oil storage tank depends on the amount of water in the tank and thus the location of the water/oil interface line on the side of the tank.

HOW WATER GETS IN to OIL TANKS - How water gets into an oil storage tank

Bad oil tank filler location

Water, enters a heating or fuel oil tank from a poorly sealed fill box which is flush with the ground or which is located below a roof edge, from missing fill pipe or vent pipe caps, from loose pipe fittings, and less commonly, from water delivered with fuel from an improperly maintained bulk storage facility.

Condensation inside oil tanks and groundwater leaks into oil tanks

In outside above-ground tanks water also often enters the fuel oil tank from condensation as temperatures change, particularly when the tank is not kept filled. Above ground tanks in cold climates may be exposed to temperature variations drawing and expelling air from a partly-empty tank. When warm moist outdoor air is drawn into a steel tank, moisture in the air may condense and accumulate in the tank.

Water can also leak into a tank from ground water when the oil level is low if the tank is damaged. [R.W. Beckett Corporation, Technical Information Bulletin, October 15, 1990.]

Delivery of bad oil

Most oil delivery companies store their product in very large storage tanks near a rail or waterway delivery point. Large oil storage facilities may deliberately keep water in the bottom of those tanks so that if the large (above ground oil storage depot tank) begins to leak, water will leak out first and thus be observed before there is a large oil spill.

An oil truck which is filled when oil has just been delivered to the oil depot tank might in unusual circumstances pick up excessive amounts of water in the oil it obtains, thus potentially delivering it to its customers. Equipment is often used to attempt to trap and filter water in oil and other fuel delivery systems to reduce this risk.

IMPROPER OIL TANK INSTALLATION - Improper oil tank installation can cause leaks

Placing a tank in cinders or ash or acidic soil: tanks set in beds of cinders or ashes cause outside-in corrosion and leaks.

Tanks may also be damaged by being dropped or pushed into the excavated hole rather than being carefully lowered by a rope.

Burying an indoor-rated tank: That an installer would bury an indoor-rated 275-gallon tank outdoors may come as a surprise to some readers but I've been surprised at how often we've found either completely or partially buried indoor-tanks.

At least on older oil tanks (perhaps before 2000), the UL label affixed to the tank explicitly says "indoor use only" right there for the installer to read. I contacted a few manufacturers and wrote to UL to ask if it was a building code violation to bury a tank with this indoor use rating. I haven't received a reply, but interestingly, newer 275-gallon steel oil storage tank UL rating labels simply dropped the wording that indicated where the tank could be used. Our concern was that an indoor-rated tank may lack the thickness of steel or an anti-corrosion coating that a buried tank needs.

Placing an indoor-rated tank outside with no weather protection also risks water entry in the tank (from roof spillage or condensation), gelling of the oil and loss of heat in cold climates, and perhaps extra corrosion.

MECHANICAL DAMAGE - Mechanical damage to oil storage tanks

oil tanks may be damaged during their installation, such as being dropped or gouged against a rock or other item which scratches or dents the tank, increasing its vulnerability to outside corrosion.

While it's speculative (we have no field data on this item) tanks or tank piping may be damaged by vehicle traffic in some locations as well.

IMPROPER OIL TANK PIPING - Improper oil piping can cause leaks

Oil tank piping materials or connections can lead to oil leaks. If you didn't know, residential oil tanks are usually filled under pressure. The oil filler nozzle is actually linked to the top of the inlet pipe and the truck pumps into the tank at pressure - most-likely to speed the delivery process. This fill-pressure can be considerable and can cause leakage or even catastrophic tank failure and leaks into a building if the tank piping is improper or if the tank is damaged.

• At an above-ground or indoor oil storage tank a small amount of seepage around the oil filler pipe is normal - having installed oil piping the author testifies that it requires very good workmanship to avoid this seepage as the tank top thread tapping and 2" steel pipe thread tapping can be a bit crude. If oil is running down the tank onto the floor or causing an odor problem this connection needs to be re-made. Because the work can be troublesome (a filler pipe disassembly may require demolition at a house wall) it should not be done unless really needed.
• At a buried oil storage tank loose or improper oil filler connections at the top of a buried tank or anywhere in the piping run can leak onto outdoor soil (luckily usually not deep underground) or indoors in a building.
• Under-sized oil storage tank fill or vent piping can cause very serious oil leaks inside the building or outside, including catastrophic oil leaks if a (plastic) pipe breaks.
• The most catastrophic in-building oil storage tank leaks are not from rust perforation itself as such leaks are usually slow drips. Extreme indoor oil contamination occurs in more unusual and very serious circumstances when indoor oil tank has been removed from a building, for example on conversion from oil to gas heat, but the oil filler pipe was left outside and through the house wall, though no longer connected to a tank inside.
  
  In an instance in Ulster County, New York, the contractor left plywood outside nailed against the building to prevent access to the old filler pipe pending its removal. But a neighbor called her oil company with an out-of-oil "no heat" condition in very cold weather. The oil delivery driver, intending to assist in an urgent case, went to the wrong house, removed the plywood, and pumped hundreds of gallons of oil directly into the home's basement.

OIL TANK SOIL CONDITIONS - Soil conditions as a contributor to buried oil tank failure

If a soil is acidic and particularly in areas where there is also a lot of groundwater or surface or roof runoff around a buried oil tank, the corrosivitiy of the soil may be a factor in oil tank external corrosion and ultimate leakage

Manufacturing defects: such as defects in the coating of a steel tank to be buried or poorly-welded seams may result in underground oil leakage. I have not seen reports of this occurrence - this may be a theoretical rather than a significant risk.

Health Hazards of Exposure to Heating Oil Fumes

OSHA's position is that heating oil fumes are a nuisance and may not pose a hazard to a healthy individual. Our field investigation experience as well as a review of oil spill guidelines from several sources provide anecdotal and other evidence that the elderly, infants, or people who are in fragile health, as well as people who suffer from multiple chemical sensitivity, allergies, asthma, and some other respiratory conditions may experience more serious symptoms including asthma attacks and other complaints.

Several U.S. states including the Connecticut department of health provides a fact sheet on home heating oil spills that includes the advice that homeowners should avoid both breathing heating oil fumes and skin contact with heating oil. The Wisconsin Department of Health Services offers similar advice. The US ATSDR (Agency for Toxic Substances and Disease Registry) also provides a Public Health Statement for Fuel Oils and related documents including Heating Oil Exposure Health Effects and ATSDRs section on Heating Oil Chemical Properties.

A typical No. 2 home heating oil MSDS document includes the hazard identification information for home heating oil that we list below. The same document provides information about toxicity levels - the exposure necessary for serious medical effects to be at risk or to actually occur.

• Eye contact with heating oil: Contact with eyes may cause mild irritation. Flush with clean water for at least 15 minutes.
• Skin contact with heating oil: Practically non-toxic following a single acute exposure; may cause skin irritation with prolonged or repeated contact; liquid may be absorbed through the skin in toxic amounts if large areas of skin are repeatedly exposed. Remove contaminated clothing, wash with soap and water or waterless hand cleaner; seek medical attention of skin redness develops.
• Inhalation of heating oil [presumably refers to liquid inhalation?]: excessive exposure may cause irritation of the nose, throat, lungs, and respiratory tract. Central nervous system (brain) effects may include headache, dizziness, loss of balance and coordination, unconsciousness, coma, respiratory failure, and death.
  
  MOVE TO FRESH AIR - provide artificial respiration (CPR) if necessary - seek immediate medical help.
• Ingestion of heating oil: major threat occurs from vomiting and breathing liquid drops into the lungs; aspiration [presumably of liquid heating oil drops] can lead to chemical pneumonia (fluid in the lungs), severe lung damage, respiratory failure, or death.
  
  DO NOT INDUCE VOMITING - seek immediate medical help.
  
  Ingestion of heating oil may also cause gastrointestinal disturbances, irritation, nausea, vomiting, diarrhea, central nervous system (brain) effects similar to alcohol intoxication, and in severe cases of heating oil ingestion, effects may lead to tremors, convulsions, loss of consciousness, coma, respiratory arrest, and death.
• Flue gases produced by burning heating oil in an area without adequate ventilation [presumably also where a chimney is not venting properly] may result in hazardous levels of combustion products, including carbon monoxide, and inadequate oxygen levels that can cause unconsciousness, suffocation, and death.
• Carcinogenicity of heating oil: [cancer risk from home heating oil exposure]: similar products have caused skin cancer and systemic toxicity in laboratory animals following repeated applications. The significance of these results to human exposure has not been determined.

Exposure Limits for No. 2 Home Heating Oil

The following workplace exposure limit for heating oil is quoted from ATSDR.

The Occupational Safety and Health Administration (OSHA) and the Air Force Office of Safety and Health (AFOSH) regulate levels of petroleum products in the private sector and Air Force workplaces, respectively.

The maximum allowable amount of petroleum products in the workroom air during an 8-hour workday, 40-hour workweek, is 400 parts of petroleum distillates (naphtha) per million parts of air, or more simply stated, 400 ppm.

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OIL TANK FAILURE CAUSES
  OIL TANK LEAK or FAILURE MECHANISMS
  OIL TANK RUST PERFORATION
  HOW WATER GETS IN
  IMPROPER OIL TANK INSTALLATION
  MECHANICAL DAMAGE to OIL TANKS
  IMPROPER OIL TANK PIPING
  SOIL CONDITIONS IMPACT ON OIL TANKS

• "Toxicological profile for fuel oils", U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry (ATSDR) Atlanta, GA 1995. - http://www.atsdr.cdc.gov/toxprofiles/tp75.html
• Public Health Statement for Fuel Oils, ATSDR, (the full document original source can be found at http://www.atsdr.cdc.gov/toxprofiles/phs75.html). An excerpt from this document is just below. ATSDR,
  Division of Toxicology, 1600 Clifton Road NE, Mailstop F-32, Atlanta, GA 30333 888-422-8737.
• Heating Oil Exposure Health Effects - The ATSDR section on health effects of exposure to heating oil see-ATSDR
• Heating Oil Chemical Properties - ATSDR
• Potential for Human Exposure to Heating Oil - ATSDR

  1.5 How can fuel oils affect my health?

  We know very little of the human health effects caused by fuel oils. Daily use of a kerosene stove for cooking should not cause any breathing problems for most people. People who use kerosene stoves to cook do not have more colds than people who have other types of stoves. Breathing moderate amounts of deodorized kerosene (fuel oil no. 1) has been shown to slightly affect the ability to smell and to cause a taste sensation. Numerous case-studies have reported accidental poisoning in children as the result of drinking kerosene. These accidents are probably much more frequent in areas where kerosene is commonly used for cooking and heating. Drinking kerosene may cause vomiting, diarrhea, swelling of the stomach, stomach cramps, coughing, drowsiness, restlessness, irritability, and unconsciousness; also, it may be difficult to breathe, and breathing may be painful. Coughing, pneumonia, and difficult or painful breathing after drinking kerosene suggest that kerosene has entered the lungs. In addition, drinking large amounts of kerosene can put you into a coma, cause convulsions, and may even cause death. When kerosene gets on your skin for short periods, it can make your skin itchy, red, and sore; sometimes blisters may occur and your skin may peel.

  Breathing fuel oil no. 1 vapor for periods as short as 1 hour may make you feel nauseous, increase your blood pressure, be irritating to your eyes, or make your eyes bloodshot. Breathing kerosene or JP-5 vapors can also affect your nervous system. Some of the effects that have been noted in case studies include headache, light-headedness, anorexia (loss of appetite), poor coordination, and difficulty concentrating. Breathing diesel fuel vapors for a long time may damage your kidneys, increase your blood pressure, or lower your blood's ability to clot. Constant skin contact (for example, washing) with diesel fuel may also damage your kidneys.

  It appears that repeated contact with fuel oils can cause skin cancer in mice and may cause liver cancer in mice. However, there is some conflicting information. Further, the fuel oils were tested only on mice. We do not know if fuel oils can cause cancer in humans. The International Agency for Research on Cancer (IARC) has determined that residual (heavy) fuel oils and marine diesel fuel are possibly carcinogenic to humans (Group 2B classification). In addition, IARC considers that there is not enough information (Group 3 classification) available to determine if distillate (light) fuel oils or distillate (light) diesel fuels cause cancer. They have also determined that occupational exposures to fuel oils during petroleum refining are probably carcinogenic to humans (Group 2A classification). We do not know if fuel oils can cause birth defects or if they affect reproduction.

• "Home Heating Oil Spills, Fact Sheet", Connecticut Department of Public Health
• "Home Heating Oil Spills", Wisconsin Department of Health, at http://dhs.wisconsin.gov/eh/Air/fs/Oilspill.htm
• MSDS for No. 2 Home Heating Oil - provided by Hess Oil Company

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