The National Oilheat Research Alliance recommends that storage tanks be replaced after 30 years of service no matter how good they look on the outside. Tanks corrode from the inside as well by “pitting” in the steel. Starting in September 2009, Oehlert Bros. started replacing tanks exclusively with Granby GreenShield tanks which are constructed with a double bottom and include a leak detection system! These tanks have a superior finish and boast warranties of up to 25 years! If your heating oil tank has been in service for more than 30 years, it is a must to replace it before it leaks and causes an expensive cleanup.