One of the conditions of the sale of the house was that we would be responsible for replacing our oil tank. As it was 22 years old, it did need changing. I have been in a house where their oil tank leaked, and the smell of oil that remained for months after the cleanup was enough to prompt me to look into a double bottom tank with an alarm feature. If the oil breaches the first wall into the emergency reservoir, a whistle sounds to alert you. This way we don't have to worry about stinky oil, and have time to replace the tank.