Guide to Heating Oil Storage Tank Defects: How to Inspect & Report Defects in AST & UST Installations InspectAPedia® -
Example oil tank inspection report language for above ground or buried oil tanks
Oil tank location errors - where not to put the oil tank, & general warnings about buried oil tanks
Reporting that an oil tank is patched, leaky, poorly supported
Reporting oil piping defects, leaks, errors
Guidelines for home inspectors for reporting on oil storage tanks
Questions & answers about heating oil storage tank inspection, diagnosis, & repair: location, leaks, piping, regulations
This fuel oil storage tank article describes common defects & problems found at above ground and buried oil storage tanks for both above ground oil storage tanks (ASTs) and underground or buried oil storage tanks (USTs). We discuss problems with oil tank contamination by water or dirt, oil tank location and clearances, oil tank rusting and leaks, oil tank leak testing, oil tank piping, oil tank support and protection from damage, oil piping safety valves, & how to avoid trouble with oil tanks that are exposed to cold weather.
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OIL TANK DEFECTS - Reporting Oil Tank Defects by Visual Inspection
This document describes and provides home inspection report language for defects in heating oil tanks, oil piping, and other oil storage tank installation defects that can be found by visual inspection for both above ground storage tanks (ASTs) and underground oil storage tanks (USTs).
Beyond the costly problem of leaky heating oil tanks, this document lists other important safety or
oil-fired equipment operational defects in home and light commercial heating oil storage and piping systems.
This sample home inspection report language may assist home owners or home buyers in understanding
risks associated with both buried and above ground oil or other fuel storage tanks at their property.
The oil tank and oil piping inspection report language explains the need for action and indicates where
more information can be obtained.
Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
Also see OIL TANK INSPECTION REPORTS and see the oil tank report text and oil tank defect photographs at Visual Inspection of Oil Storage Tanks.
NOTICE: while example report language is provided here, reproduction of this or any of our web pages or their contents online at other websites
or in printed documents for sale is prohibited. Readers are welcome to use the text directly in home inspection reports, with citation of the website source.
OIL TANK IN GARAGE - Oil Tank in Garage - warning
The tank is in the garage. Caution: Don't hit the tank with your car - a leak could involve a costly cleanup. Some municipalities require protective caging or barriers be built around the tank
to avoid this hazard.
OIL TANK NEAR WATER - Oil Tank - nearby waterway, risks & code HAZMAT
*** Nearby waterway
or Adjacent property
(estimated within ___') formed by the
stream (or other body of water) would be contaminated should this tank leak or fall over.
The OIL TANK at this location without protection is in possible violation of NYS Building Code 1002.2b and 1002.4c
"Above ground tanks shall be provided with means to prevent accidental discharge from spreading to waterways,
OIL TANK TOO CLOSE TO FURNACE - or Boiler or Water Heater - Oil Tank Clearances from Equipment
Technical Safety Recommendation: The oil tank may be located closer than recommended
distance from the boiler. You should discuss this question with your heating service person.
Our sketch at left, courtesy of Carson Dunlop, shows the typical ten foot clearance recommended between the closest point of the oil tank and the closest point of an oil burner.
OIL TANK SAFETY CLEARANCE from heating equipment - Building and Fire Code Citations
NYS Uniform Fire Prevention and Building Code, 1/1984 Para. 1002.3b.
"--- tanks must not be closer than 5 ft to the
burner, boiler, or furnace---" Domestic Oil Burners, Burkhart, McGraw
Hill, 1969 p. 174.
Other experts suggest a minimum of 7' or 10' separation between the closest
point of the tank and boiler. "The Modern Service Manual for Residential
Oil Fired Equipment", NOTA, & National Association of Oil Heat
Managers, 1979, illustration in section on "Oil Tank and Piping".
This Audel Oil Burner Guide sketch (left) shows that the minimum ten-foot clearance rule between an oil tank and the boiler, furnace, or water heater, is an old one dating at least from 1947 in the U.S.
OIL STORAGE TANK EXPOSED TO WEATHER - Outside Oil Tank, (not buried) Exposed to Weather
Caution: As this home heating oil tank is outside, it is exposed to water entry either through
roof spillage onto the tank and splashing into the the filler or vent pipes.
Water may also accumulate in this outside oil storage tank by condensation due to temperature changes.
Water in heating oil can cause loss of heat if it reaches the oil filter or oil burner. Water in heating oil
tanks also often leads to internal corrosion and leaks in the oil storage tank itself, possibly ending in a costly oil leak or spill.
Keep roof spillage off of the tank top by adding a roof or enclosure over or around the tank;
Test the oil tank for water presence and remove any excessive water;
Use a fuel oil additive such as 4 in 1 Hot(TM) to assist in removing moisture from the oil. Photograph courtesy of Arlene Puentes]
This is a new heating oil tank (rated for indoor use according to its UL label) located outdoors. If you click-on and enlarge Ms. Puentes' photograph
of this oil tank you will see that its top is wet from roof spillage and splash and that water runs down the side of the tank.
The fill and vent
piping on this tank appear intact from the photo but the tank and its heating oil contents have other risks which we discuss in this
oil tank inspection report sample text section.
When an indoor-use heating oil tank is located outside it is exposed to water entry either
through spillage (such as from a roof edge shown in this photo) onto the fill and vent pipes or by condensation due to temperature changes.
Water in the fuel oil or simple exposure of the oil to cold temperatures can lead to loss of heat
and resultant damage to a building by several means:
oil tank leaks caused by water in the oil tank, which will reside at the bottom of the tank, may freeze in the tank
or in the oil line, particularly for installations at which the oil line is attached to the
bottom of the tank.
oil burner damage: water can cause rusting which is pulled into the heating equipment where it clogs the filter, fuel pump, or
oil burner nozzle
heat loss: in some modern high efficiency systems a special filter is used which will stop flow completely, shutting
down the burner in response to water or debris buildup in the filter - a move to protect the equipment.
heat loss: heating oil in an outside line may "Jell" and stop flowing at cold temperatures.
Heat tape fire hazards at heating oil piping: outside tanks in cold climates exposed to jelling of the heating fuel may be (in error) fitted with
a heating tape in an attempt to avoid freeze-up in the oil line itself. This is a potential fire hazard.
Heat tapes should not be used on heating oil lines. Details are at HEAT TAPE HAZARD ON OIL TANK. Also see FREEZE-PROOF A BUILDING where we describe GFCI protection on heat tape circuits powering heat tapes for manufactured and mobile homes.
Water in oil tanks also often leads to internal corrosion and leaks in the tank itself, regardless of the tank location, though
buried tanks and indoor oil tanks are less prone to water accumulation due to in-tank condensation in response to temperature changes
than a tank located above ground outside.
Oil storage tanks usually fail from rust perforation due to combination of water inside the tank with sulphur in the fuel oil.
External rust, unless very heavy, isn't highly correlated with internal rust.
A new tank, when required, may cost more $2000. installed, including removal of the old oil tank.
When an outdoor tank is exposed to these conditions and even for an indoor tank which we suspect
has had a dose of water and sludge, we recommend regular use of a heating or fuel oil additive
to absorb water and to help break up sludge. The best solution is to locate the tank indoors or to build a
heated shelter over the outdoor tank.
How to Keep Water Out of Your Heating Oil Storage Tank and Avoid Loss of Heat
Keep the oil tank filled as near full as you can to minimize the tendency of the tank to draw in moist air
and experience in-tank moisture condensation. Don't leave the oil tank near empty over the spring or summer months.
Keeping Water Out Of Above ground Oil Tanks Located Outside
Protect the oil tank from spillage from roof runoff
Be sure that the oil tank filler opening cap is kept in place and sealed and that the oil filler cap o-ring or gasket are in good condition
Be sure that the oil storage tank vent pipe is properly capped (a straight pipe pointing up with no cap permits water entry) (and also screened against
insects which can clog the vent opening and lead to tank leaks)
In cold-weather climates, enclose the tank on all sides, giving access for inspection; route fill and vent pipes outside of the enclosure;
where needed, provide a small heat source either from the building or by electric heater or even a light bulb to prevent freeze-ups. At least one manufacturer presently sells an outdoor plastic oil tank enclosure for this purpose, though we haven't seen how they're providing a heat source to avoid oil waxing.
Use a heating oil additive which will help remove small amounts of water - see "Heating or Fuel Oil Additives" below.
Route oil lines from the top of the tank rather than the bottom to reduce pick-up of water from the tank bottom.
At annual service have the oil storage tank checked for water and remove water if it's found there.
[Photo courtesy of Arlene Puentes.
This photo shows an un-screened oil tank vent pipe which may also be under-sized. The 90 deg. ell at the top of the pipe nipple is incomplete
protection against water entry if roof spillage splashes on the tank top, and it lacks an insect screen. This is not an approved nor recommended
oil tank venting detail.
Keeping Water Out Of Underground Oil Storage Tanks
Extend oil tank fill and vent valves above ground level to reduce the chances of surface water entering the piping
At annual service have the oil storage tank checked for water and remove water if it's found there.
If water is found in the oil tank, and if the oil delivery company is certain that they didn't deliver water from their tank,
and if water is not entering by condensation and temperature change cycles, check the tank piping connections for leaks.
Have the tank [low] pressure tested for leaks.
Take oil piping off of the top of the buried oil tank, not the bottom.
Our sketch at left, courtesy of Carson Dunlop, shows a common buried oil tank installation except that the oil line is shown leaving the bottom of the buried oil tank.
Modern practice usually connects a pair of oil lines to the top of a buried oil tank, avoiding picking up water and sludge from the oil storage tank bottom, and avoiding the chance that a leak in piping between oil and building interior will flood the inside of the building with oil.
Tips for Using Heating or Fuel Oil Additives in the Oil Storage Tank
Heating fuel additives such as "4-in-One Hot" (TM) can
help prevent loss of heat by adding a pour point depressant which
lowers the temperature at which the heating oil will form waxes or jell, and by adding a chemical, typically an
alcohol, to remove [small amounts] of water from the oil. Such additives may also help break up sludge which tends
to clog old heating oil lines.
Some oil companies will deliver a mix of heating oil and kerosene to outdoor above ground oil tanks as a way to
avoid jelling and freeze-ups and loss of heat. It may be less costly to buy regular heating oil and put in the
appropriate pour point depressant additives at each oil delivery.
Note: these tips are not a complete oil tank installation guide. Proper installation must be
done by trained service technicians and must comply with local building codes.
It is also diagnostic to test the amount of water present in tank bottom; and water should be pumped out.
Water mixes with sulphur in the fuel, forms sulfuric acid, and corrodes through the tank.
While we've found them lasting longer, a common life expectancy of buried tanks is 10-15 years.
Ask your service person about using a fuel additive such as 4-in-1-Hot™ to help remove water.
It will also increase heating system reliability.
ENVIRONMENTAL ISSUES CONCERNING BURIED OIL TANKS: the NY Department of Environmental Conservation has a program registering
buried oil tanks at any site storing more than 1100 gallons of heating oil. Eventually this
concern may spread to smaller residential tanks. The concern is for leaks which contaminate the environment.
OIL STORAGE TANK FAILURE RATE: Oil storage tanks usually fail from rust perforation due to combination of water
inside the tank with sulphur in the fuel oil. External rust, unless very heavy, isn't highly correlated
with internal rust.
A new tank can involve significant expense.
There are also proper methods of "abandoning" old unused
buried tanks without removing them if the tanks have not leaked. Consult your heating company or local
DEC officials if you have questions regarding this topic.
In New England for a two year period [1984-5] among customers who had buried
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.
Source: Fuel Oil and Oil Heat magazine, August 1985 p.18.
OIL TANK TESTING: specialty companies and some oil companies have equipment to test tanks for leaks.
Testing for water in the tank is simple and can be done by any service person.
OIL TANK SUPPORT - Oil Tank legs need masonry piers or tank support piers are out of level
"Oil Tank legs for this outdoor tank should be supported by level and sound masonry piers to reduce the
probability of the oil tank feet sinking or tipping and causing the tank to tip over.
Tipping or falling outside above ground oil tanks risk
a fire, heating oil spill, or a "loss-of-heat" hazard.
This repair/maintenance item should not be deferred. This is usually
an inexpensive item to correct."
[Photo courtesy of Arlene Puentes]
See OIL TANK SUPPORT for full details about proper support and protection for above ground oil storage tanks.
OIL TANK LEAKY/PATCHED - Oil Tank Leaky/Patched - replace soon
"The oil tank is very likely to have to be replaced soon if not immediately - the tank was leaking and
a "patch" has been strapped to the tank bottom.
Removing old tanks and installing are placement oil tank will involve significant expense.
WARNING: serious and costly oil tank spillage can occur at any moment, but especially when this oil storage tank is being filled."
Defects in oil fill or vent piping are much more serious than you may think. That little drip of oil onto the basement floor is just a clue - but when your heating equipment is running, air drawn into the oil line at that same leak point can lead poor or dirty oil burner operation, a dangerous puffback, or loss of heat and related building damage. And defects in the oil fill and vent piping can lead to catastrophic indoor or outdoor oil spills (as we explain at OIL TANK PRESSURE).
Please see our detailed articles about heating oil piping inspection and defects beginning at OIL TANK PIPING & PIPING DEFECTS. Details and subtopics are at:
MISSING SAFETY CONTROLS & SWITCHES at the Oil Tank & Oil Burner: Electrical shutoff switches for heat and oil line shut off valves
Oil heating equipment safety controls are discussed in detail at FIRE SAFETY CONTROLS where we provide more information on oil heat equipment electrical switches and on the fusible-link oil supply piping valve, check valve, or related controls that help prevent pumping heating oil onto a building fire as well as avoiding other oil piping problems.
Questions & Answers regarding this article
Questions & answers about heating oil storage tank inspection, diagnosis, & repair: location, leaks, piping, regulations
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Additional technical contributors & reference sources for this article are listed below.
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Arlene Puentes, an ASHI home inspector in Kingston, NY, contributed the example photograph of an outdoor aboveground oil tank. Ms. Puentes can be contacted at ap@octoberhome.com
Dave Ferris - M&S Environmental Systems, Dutchess County, New York. Mr. Ferris was an HVAC expert. Personal communication to DJF 1987. Remove the firematic or fusible oil supply line valve on return oil-line side - in case of fire if this one closes first the pump continues to run, blows its seal, and sprays oil all over the fire. Proper installation is to have a fusible link valve only on the supply side, and to install a check valve on the return line to prevent back-siphonage from the tank.
Audels Oil Burner Guide, Installation, Servicing, Repairing, Frank D. Graham, 1940's edition (obsolete). Updated versions of this guide are available in various editions, 1947, 1950, 1955, 1958, 1959, 1962, 1965, 1967, and at prices from around $3.00 to nearly $70.00 - useful for simple, clear, but not current, explanation of how heating equipment works. The original retail price was $1.00.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Oil Tanks - The Oil Storage Tank Information Website: Buried or Above Ground Oil Tank Inspection, Testing, Cleanup, Abandonment of Oil Tanks
Abandon a Buried Oil Tank, How To - Abandoning Commercial Underground Tanks, Russ Brauksieck, ASHI Tech. Journal, Vol.3 No.1 Spring 1993, P. 40-41 [Reprint]
Petroleum Bulk Storage J. Sibblies, NY State DEC, Advice to Home Owners and Home Inspectors about Oil Storage Tanks - summary from ASHI Chapter Seminar.
Septic Tank inspection, testing, diagnosis, repair
OIL TANK FAILURE CAUSES - Oil Tank Failure Causes - oil tank leaks are caused by corrosion, damage, soil conditions, other factors
TANK FAILURE RATES - Oil Tank Failure Rates - Oil Tank Leak Probability as a Function of Tank Age, Location, Condition, Soil Conditions and Other Factors
OIL TANK TESTING - - How Oil Tanks are Tested for Evidence Leaks, of Current or Previous Oil Spills
National Association of Oil Heat Service Managers, PO Box 380, Elmwood Park, NJ 07407
"Homeowners Guide to Fuel Storage," Agway Energy Products, Verbank, NY, November 1990
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