Oil tank taking water (C) Daniel Friedman How Water Gets Into Above-Ground Oil Tanks

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This article explains how water gets into above-ground oil tanks. This article series explains the problems caused by water accumulation in oil tanks, how water gets into the oil tank, how to measure water in the oil tank, how to remove water from oil storage tanks regardless of whether the oil tank is indoors, outdoors above ground, or buried, and how to prevent water from getting into an oil storage tank.

We explain how to test for or visually check for water in a buried or above-ground oil storage tank, and how to get water out of an oil tank. Extensive free un-biased oil storage tank inspection and testing advice for property buyers and owners is provided at this website.

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How Does Water Enter an Above-Ground Oil Storage Tank

Missing oil filler caps (C) Daniel Friedman

Sources of water entry into above ground oil storage tanks are similar to the underground oil tank water leak sources listed at BURIED OIL TANK WATER ENTRY. Here we list additional ways that water may leak into an above-ground oil storage tank besides the ones in that earlier list for buried tanks. [Paraphrased, edited, and expanded from R.W. Beckett]:

[Click to enlarge any image]

  • Water may enter an above-ground oil storage tank from a fill pipe that is not properly capped, sealed, and located out of the roof edge drip line.

    Our photo (left) of an outdoor oil storage tank shows that the oil tank vent is not protected against water entry, and worse, though you can't see it in this closeup photo), this outdoor oil tank was located close to the building (the usual practice) placing it right under the drip line of the roof.

    Whenever gutters overflowed (which is common), water splashing on the oil tank to was at risk of entering the tank through this vent pipe.

Water may enter an above-ground oil storage tank from a vent pipe that is not capped, shielded from water entry, and located away from roof edges. Note that water spilling on to the top of an outdoor oil storage tank can splash-up and enter the oil tank through the vent pipe even if the pipe has a rain cap installed.

Above ground oil storage tank (C) Carson Dunlop Associates

  • Outdoor above-ground oil storage tank water condensation occurs when a partially-filled oil tank is exposed to variations in outdoor temperature. Oil in the tank and the tank steel itself are warmed by sunlight and higher daytime temperatures.

    The above-ground oil tank illustration (left) is provided courtesy of Carson Dunlop Associates.

    At higher temperatures both air inside the free area in the oil storage tank and the oil itself expand in volume, pushing air out of the oil storage tank.

    As temperatures fall after sundown or in night time temperatures, both air and oil volume in the oil tank are reduced in volume.

    This volume reduction of air and oil inside the oil tank will draw night-time air into the oil tank through the oil tank vent pipe opening. When that incoming air is high in moisture, moisture will condense on the oil tank interior walls, accumulating on the oil tank bottom (water is heavier than oil).

    When the quantity of water on the oil tank bottom is great enough to reach the oil supply piping (for oil tanks whose piping is attached through the oil tank top), or when it reaches an oil supply line outlet at the tank bottom (for oil tanks piped off of the tank bottom), water enters the heating system oil burner, leading to lockout or loss of heat.

Home buyers should be sure to review OIL TANK LEAK TEST METHODS - Leaky Heating Oil Tanks - How Oil Tanks are Tested for Evidence Leaks, of Current or Previous Oil Spills and TankLegal Issues - Home Buyers and Home Owners Guide to Leaky Heating Oil Tanks - What to Do About & When to Report Oil Tank Leaks. Leaky Heating Oil Tanks.

Home owners who have old oil tanks above ground or any age oil tank below ground should also be sure to review OIL TANK ABANDONING PROCEDURE - Abandoning Commercial vs. Residential Underground Oil Storage Tanks (UST) - Procedures & Regulations A separate website addresses Septic Tanks.

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