A double wall tank, otherwise known as a bunded fuel tanks or self bunded fuel tanks, offer the most effective solution to the economical and safe  storage of fuels on site.A bunded tank, by definition, is a tank within a tank. The inner tank serves as the storage for the fuel and the outer tank serves as the spill or leak containment system or as we like to call it the protective jacket. This is otherwise known as the 'bund'. The space between the inner and outer tanks serve as the bund, and are 110% of the capacity of the inner tank eliminating the need for an external spill containment system or a masonary bund wall as the chances for an overfill accident  to occur gets reduced drastically. This makes  bunded tanks as one of the most environment friendly combustabile  liquid storage options, as the risk of pollution is mitigated to a very high level.