Abstract: A tanker trailer includes tanks mounted one behind the other to a chassis using a flexible mounting system. The mounting allows individual tank movement in upward and downward directions from a rest position. Close nesting is accomplished by provided adjacent tanks with complimentary curved ends. The tanks may have progressively increasing depths from the front to the rear of the trailer. Two sight gauges disposed on a diameter passing through a volumetric center line provides a means of assessing the quantity of liquid in the tank. Alternatively, a single gauge may be used in conjunction with a level meaning device on a horizontal line intersecting the volumetric center line and the gauge. A vapour recovery system includes two volumetrically matched members mounted within the tank equidistant from the volumetric center line one of which serves as a vent pipe.