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Visual Inspection of Above Ground Residential Heating Oil Storage Tanks - Above Ground Oil Tanks Used Outdoors InspectAPedia®  -   Above ground outside oil tanks Water in oil tanks - sources, problems Heating oil additives and chemicals for outdoor oil tanks

How to inspect above ground oil storage tanks (ASTs), whether above ground outdoors indoors: This article discusses the risks of heat loss or leaks when above-ground outdoor oil storage tanks are used outside. It explains how water gets into oil storage tanks no matter where they are located, above ground oil tanks, buried oil tanks, or even possibly indoor oil tanks. Photograph at page top courtesy of Arlene Puentes.

The article explains the problems caused by water in oil tanks and also the problems faced by owners of above ground oil storage tanks located in cold climates. This article is a sub-chapter of OIL TANK INSPECTIONS

This article, sketchs, and photographs give advice and example photos for the visual inspection of above ground oil tanks for leaks and damage including damaged or leaky oil storage tanks, improper oil tank piping, valves, and indoor-type oil tanks located outdoors. Sketch of an above ground outdoor oil storage tank is courtesy of Carson Dunlop.

Here are a some important indicators of tank condition that any home inspector can include when an oil storage tank is visible and accessible inside or at a building. Readers whose heating system uses an above-ground outdoor oil storage tank should be sure to also read HEATING OIL CLOUD WAX GEL POINT and OIL TANK SLUDGE.

Also see additional visibly detectable oil tank defects listed at Home Inspection Report Language Library: Visible Defects in Oil Tank Installations, Tanks, and Heating Oil Piping.

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Guide to Issues with Indoor-rated Oil Storage Tanks Used Outdoors

Problems Faced by Above Ground Outdoor Oil Storage Tanks

How Water Gets Into Oil Storage Tanks Water can enter an oil storage tank by more than one means: Water may collect in an oil storage tank, above ground or buried, or in some cases even indoors, when the oil is left at low levels in the tank for long periods, particularly in periods of cool weather or in periods of alternating warm humid and then cool weather. As temperatures change around and then in the oil tank, warm moist outside air is drawn into the oil storage tank through its vent. Moisture in the air condenses on the cool tank interior surface, and can accumulate in the tank. Water may enter an oil delivery truck by the same means as just discussed above for oil tanks. From the oil delivery truck water, along with oil, may then be pumped into the property owners oil storage tank. Some oil companies are quite diligent to avoid these problems or to include water filters on their delivery trucks. Water may enter an oil storage tank by delivery of a "bad" batch of oil from the oil delivery company. Those huge commercial oil storage depot tanks you may see, perhaps near a railroad line or a river, may be deliberately maintained with a few feet of water in the bottom of the tank so that if a leak occurs it can be discovered as escaping water before the actual oil leaks out. When an oil company truck is being filled from one of these tanks, in some conditions some of the larger tank's water can enter the oil delivery truck tank where under some circumstances it can also be pumped into the homeowner's oil tank. Water may enter an outdoor oil storage tank from roof runoff (rain or melting snow) spillage onto or near the oil filler or vent line for an oil tank. I've seen this condition both at above ground tanks which were placed under the house eaves (right where roof spillage fell onto the tank) and also at buried tanks whose filler pipe was set flush with the ground.

Problems Caused When Water Enters an Oil Storage Tank? What happens when an oil tank is outdoors? Water can enter the oil storage tank where it causes possibly serious problems for the heating equipment. 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: The photo shows an oil tank which is half buried outdoors under a deck. Was this tank intended for outdoor use at all? If so, was it intended for use when in contact with the ground? Probably not. The risk is tank rusting, water entry, oil leaks, and related problems we've already listed. In cold climates, 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. In warm, moderate, or cold climates water in the oil storage tank can cause rusting which is pulled into the heating equipment where it clogs the filter, fuel pump, or oil burner nozzle In some modern high efficiency systems a special filter is used which will stop flow completely (such as the "System 2000" heating boiler), shutting down the burner in response to water or debris buildup in the filter - a move to protect the equipment. In cold climates, heating oil in an outside oil tank supply line may "Jell" and stop flowing at cold temperatures. Fire risk: Outside above ground oil storage 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.

Outdoor oil tanks in cold climates risk loss of heat from freezing water or jelling fuel as we just cited. In the photo shown here the oil lines are taken off of the top of the oil tank so as to avoid picking up water that may be present in the tank, avoiding the icing problem. Note that no heat tapes are in use on the oil lines (good, that reduces a fire risk). It looks as if there has been some seepage around these oil lines, that the tank is old, and that one tank is being used to serve two oil-fired devices (two sets of oil lines leaving the tank). 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 fuel oil additive such as 4 in 1 Hot(TM) 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.

Heating or Fuel Oil Additives for Outdoor Oil Tanks

In cold climates, heating or fuel oil additives for above-ground outdoor oil tanks 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. I've used a product called "4-in-One Hot" which contains both a sludge break-up chemical and alcohol to help remove water from the heating oil. Such additives may indeed help break up sludge which tends to clog old heating oil lines. But I'd cite two warnings about using heating oil additives and chemicals for outdoor oil tanks:

1. No oil additive is going to remove a large quantity of water from an oil tank. Measure the amount of water present. If it's inches, your oil company can pump the water out (leaving the heating oil intact).
   
   
2. Oil additives that break up sludge might in some circumstances precipitate frequent clogging of the oil filter installed at your heating boiler or furnace since an increased amount of debris is being freed and sent along the oil lines. If you find that your boiler stops working shortly after receiving an oil delivery, check to see if the problem was a clogged oil filter. That would suggest that your tank has a lot of debris and that the debris or sludge were being stirred up whenever oil was delivered. Discuss this concern with your heating service contractor.

Pour point depressants for heating oil tanks are about the same as similar products used by owners of diesel fuel powered automobiles and trucks in cold climates, but except in dire emergency I would not recommend substituting one for the other as there are some differences in these fuels and chemicals.

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.

See HEATING OIL CLOUD WAX GEL POINT for details about heating oil waxing or jelling.

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ABOVE GROUND OIL TANK INSPECTIONS
  INSPECT VISIBLE OIL TANKS
  OIL FILL & VENT
  OIL TANK SUPPORT
  ABANDONED INDOOR OIL TANKS
  ABOVEGROUND OUTDOORS
    Indoor Tanks Used Outside
    How Water Enters Oil Tanks
    Problems of Water in Oil Tanks
    Additives for Outdoor Oil Tanks
  OIL TANK HISTORY REVIEW
OIL TANK LEAK ADVICE

LEAK CAUSES various causes of oil tank leaks
LEAK TESTING alternative ways to test oil tanks for leakage
WATER in OIL TANKS how it gets there, how to get it out, what problems it causes
TESTING COs who can test oil tanks for leaks or soil for evidence of oil leakage in the past
OIL TANK CHECKLIST This oil company's checklist they give to their delivery drivers and which is then completed and passed on to homeowners summarizes the oil industry's views of leaky oil tank warnings.

• 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
• Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors

More Information on Building Diagnostic Inspections and Repairs

• 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]
• Above Ground Oil Tanks: Visual Inspection of Oil Storage Tanks for evidence of leaks, damage, improper piping - photos and text
• Above Ground Oil Tanks Checklist, an Oil Company's advice
• Above Ground Tanks UL Standards, UL Tank Listing Standards, guidance for home owners, buyers, and inspectors
• Buried Oil Tanks - Finding How to Find Buried Oil Tanks and "Nearly Hidden" and Leaky Oil Tanks - photos and text.
• Buried Fuel tank - Advice - Buried FUEL Tank - GAS or OIL advice for home buyers, inspection report language
• Environmental Issues & Regulations for Oil Tanks, Registration, Abandonment, Leak Reporting
• Home Inspection Report Language Library: Buried Oil Tanks, Basic home buyer advice - home inspection report language suggestions
• Home Inspection Report Language Library: Visible Defects in Oil Tank Installations, Tanks, and Heating Oil Piping
• Home Inspection Report Language Library: Gas Fuel Piping or Tank Faults Basic advice - home inspection report language suggestions
• Home Inspection Report Language Library: Oil Tanks text file list © Oil and Other Storage Tank Leaks, Testing, Abandonment, Inspection - UST home inspection report language files - Reference List
• Indoor Environment Website Indoor Building Environmental Hazard Detection, Testing, Repair, & Prevention - Main Web Page
• Leaky Heating Oil Tanks - Advice for Home Owners or Buyers: caused 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
• Leak or Failure Rates for Home Heating Oil Tanks
• Legal Issues Regarding Buried Oil Storage Tanks K.S. Rea, Attorney, summary from ASHI Chapter Seminar.
• Primer on Petroleum Bulk Storage Tanks & Petroleum Contamination of Property Paul H. Ciminello, ASHI Tech. Journal, Vol.3 No.1 Spring 1993, p 35-39
• 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
• Web Link Exchange: Contact Us to list your website or contact information for oil tank testing, tank corrosion research, oil industry experts

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