Learn the basics of heating oil tanks below and see more from the information page. Also see the history of heating oil use in Oregon, ways to identify oil tanks on your property, our page on ‘How to read the “Underground Storage Tank” permit on portlandmaps.com’, oil tank decommissioning FAQ, oil tank search FAQ, how to search for tank permits.


Oil tanks, or heating oil tanks, are steel tanks which hold home heating oil #2 (diesel fuel with red dye so it can be taxes differently than fuel used for driving).

These tanks are often underground outside or above ground in a garage or basement. When buried, the tanks are cylindrical. The tanks you can see on the back of a house or in a basement are ovaloid shaped. Most underground storage tanks (USTs) are 660 or 330 gallons, most above ground storage tanks (ASTs) are 275 gallons. Chart: tank size


When in-use, these tanks connect to the furnace with one or two supply lines. Older tanks had a dedicated return line but ‘newer’ oil burning furnaces worked with only one line.

The furnace turns the fuel into a mist and ignites it, the resulting hot air/fuel mix then gets circulated into the ducts of the home. The ‘oil in the air’ is what gives heating oil the enveloping feeling that some say makes it feel warmer than other types of heating. If you are aware, you can recognize a home that has oil heat by the feel on your skin.


These residential heating oil tanks can rust over time and oil can leak into the soil. If there is a large amount of leakage it can threaten the health of people living nearby.

The Oregon Department of Environmental Quality (DEQ) has issued guidelines on the decommissioning of these tanks and approves certification for properly decommissioned tanks.

Without a certification from the DEQ buyers are finding it difficult to get a loan or financing.

Getting a certification of decommissioning from the DEQ is what home buyers want.


Washington and Oregon oil tanks were both common. Oil tanks in Vancouver and the suburbs of Portland is to be expected.

The oil tanks are usually 10′ or so away from the home. Commonly near a chimney or natural gas meter. Jack at Rush Locates has seen tanks 30′ away from homes before and in very strange places over his many years of oil tank work. Just because there is one tank doesn’t mean there isn’t another one.

ASTs or above ground storage tanks are regulated differently than USTs or underground storage tanks. If these tanks are 10% or more underground then they count as a buried tank, hence they will normally rest on legs or raised blocks. Indoor oil tanks can happen in basements, crawlspace, garages, or even what was once the outside. The DEQ considers a surface spill to be over 50 gallons. When the oil tank is indoors you’ll notice well before 50 gallons have leak out.

Need more info on a Portland Oil Tank? Call us today at 503-939-9585