Exterior above ground oil tanks have to be well supported in order to avoid the oil tank tipping over and causing an environmental hazard. The exterior oil tank should be installed on a firm pad. A cement pad with footings is best but a thick cement pad is much safer then having the tank rest on individual blocks which create a point load. When an oil tank is installed on blocks the individual blocks can sink and move under the weight of the tank and due to settling and compacting soils. The oil tank supply lines should also be protected from damage. There have been cases where these lines have been broken and damaged by falling ice an snow. Also oil tanks that are installed in the interior of a basement or crawl space should be on a firm foundation and the legs should be in good condition as not to allow the oil tank to tip over. The last thing that any home owner wants is to have the tank tip over and leak. It can cause injuy and a great deal of expensive environmental damage.