Abstract: A system for storing an organic liquid such as fuel oil comprising a tank surrounded by a containment structure forming a moat to hold any organic liquid which leaks from the tank. A drain opening is formed in the containment structure and is connected through a drain pipe to a trap. The trap houses a float actuated valve. The float actuated valve includes a valve member which has a specific gravity greater than the organic liquid fluid but less than that of water so that the float actuated valve allows water to escape from the containment structure while preventing escape of any organic liquid.