Oil tanks installed outdoors are prone to weathering and leaking. Fuel oil is primarily used for heating homes. Homeowners who have changed to gas, solar, or other sources for heating often replace their furnaces but leave the rusting oil tank in the yard. Temperature changes from night to day and season to season can cause internal condensation of water and internal corrosion.
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Storing fuel in an outdoor tank poses several problems. Water can enter the tank through condensation via the vent pipe or splashing from roof runoff. Significant moisture can affect the heating equipment indoors. Corrosion and water in the oil will lead to clogged filters and shutdown heating equipment. Corrosion can also lead to seepage or leaks.
In cold climates, the oil can gel in the lines. Water in the tank can freeze and completely block oil flow.
Inspecting Outdoor Tanks
Often, tanks rated for indoor use are placed outside. They look nearly identical and caution should be used when purchasing a tank for outdoor use. In many areas, environmental regulations require a containment pool or dike to be built around the oil tank to contain any possible spills.
If the tank appears unblemished and there are no signs of seepage around pipe fittings or elsewhere, check the date of installation. Outdoor tanks are not meant to last more than about 20 years and should be replaced as frequently as every 10 years depending on the environment.
Paint blemishes and light rust show aging. Heavy rust and scaling indicate the metal is getting thin and the tank may have to be replaced. The oil provider can pressure test the tank to see if it is leaking. Another option, particularly for underground tanks, is to have the soil tested for contamination. Look for leaks and spills at pipe joints and fittings. Dead or wilted vegetation can indicate a leak.
Large amounts of water measured in the bottom of your tank should be pumped out by the oil provider. Small amounts of water can be removed with additives that use alcohol to make the water soluble in the oil.
Gelling in cold climates can be lessened by adding "pour point depressants." These work by lowering the temperature at which the oil turns to a gel or wax.