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Tank Information

Underground oil tanks were routinely installed at house built between 1945 and 1975.  Any house built prior to 1975 is suspected of having or having had an underground oil tank on the property.  Older "historic" homes (built pre-1950) may have been converted from a coal furnace to an oil furnace in the 1950's when fuel oil became readily available. 

Fuel Storage tanks are cylindrical with their long axes oriented parallel to the ground surface.  They are typically buried 1.5 to 2.5 feet below the land surface and are filled through a two inch galvanized steel pipe.  Fill pipes have either a lockable flip cap or a brass cap that screws into a galvanized steel collar.  These pipes may be flush with the ground or they may stick up a few inches.  Bushes and landscaping often conceal fill pipes of out-of-use oil tanks. 

Fill pipes are typically within twelve feet of the house foundation and go directly down into the tank.  If an addition has been added to the house, it is possible that an out of use fill pipe could be located under or partially under the added addition. 

Because fill pipes commonly stick up above the ground surface, many property owners have unscrewed or cut off these pipes below the ground surface when the tank is taken out-of-use.  Unscrewed and cut-off fill pipes are rarely sealed properly and allow water to enter the tank. 

Vent pipes often remain at the site long after the tank is out of use.

Vent pipes are commonly present and visible even if the fill pipes have been removed.  These pipes are made of 1 to 2 inch galvanized steel pipe that has a mushroom shaped cap covering the "open" end (top) of the pipe.  (Occasionally, the pipe may simply have series of galvanized steel elbows that turn the pipe opening downward.) 

Usually the vent pipe is plumbed away from the tank and comes out of the ground vertically next to the house foundation.  (Most vent pipes do not identify the exact location of an underground tank because they do not go vertically into the top of the tank.) 

Vent pipes typically stick up 6 inches to 1.5 feet above the ground surface.  Vent pipes were not always installed on underground tanks.  Occasionally, the vent pipe is located a foot or two from the fill pipe.  These vent pipes do go directly into the top of the tank.  In rare occasions, the vent pipe is constructed of PVC. 

Depth buried:  1.5 to 2.5 feet below land surface

Tank sizes:
  • 270 gallon: 
    • typically 36 inches (3 feet) in diameter and 60 inches long (5 feet)
    • Other dimensions have been observed but are uncommon. 
  • 550 gallon tank:  either
    • 42 inches (3.5 feet) in diameter and 92 inches long (7.7 feet)
    • or
    • 46 inches (3.8 feet) in diameter and 74 inches long (6.2 feet)
    • Other dimensions have been observed but are uncommon. 
  • 1000 gallon:  We don't see many of these.  Dimensions vary. 
    • They can be anywhere from 7.7 feet to 12 feet long. 

Note: The State defines tanks larger than 1100 gallons as commercial tanks even if they were used to heat a single family residence.  Commercial tanks are subject to different assessment and cleanup requirements. 

Tank construction material:  thin gauge, uncoated steel ( slightly thicker than a US quarter).

After tank removal, numerous holes are usually discovered in the heavily corroded tanks.

Note the fill pipe, the horizontal vent pipe line, and the 2 copper fuel supply lines coming out of the top of the tank.

Tank locations on the property:  Fairly Random!  
There is no common location that tanks were installed on properties (front yard, back yard, side yard).  The tank is sometimes located near the crawl space access but not always. 

Most underground tanks are located between 4 to 10 feet away from the house foundation. Apparently, underground tanks were installed after the house foundation was poured.  Therefore, most tanks are far enough away from the house foundation for them to be safely removed.  To adequately protect the house foundation, aggressively contaminated soil excavation may not be possible.  Please see our Contamination Cleanup Page.   

Apparently, no tank installations were conducted with tank removal, replacement, or contamination cleanup in mind. 

Tank orientation:  Usually the long axis of the tank is either parallel or perpendicular to the house foundation.  Beyond that generalization, the orientation is random (parallel or perpendicular).

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