An oil tank can leak due to:
- failure of the tank body
- damage to equipment on the tank such as sight gauges
- damage to or wear-and-tear of fuel feed lines
- failure of components at the boiler end of the system, such as flexible hoses
Metal tanks can rust through, often at their bases. Plastic tanks can split due to inherent defect, age or wear-and-tear. Oil leaks can happen when oil is delivered.