Abstract: The interior of the tank of a tank truck or a tank wagon, is cleaned using a selectively removable sprayhead and the built-in delivery pump of the tank vehicle. A removable sprayhead is inserted into the interior of the tank through a manhole and connected, via the delivery pump, to an external storage source of a solvent or cleaning solution. The solvent is, for example, a mixture including a chlorinated aliphatic compound and an aromatic compound, both compounds having a freezing point below 60.degree. C. The solvent is then pumped into the tank, and the hoses normally carried with the tank truck are connected so that the delivery pump can be used to recirculate the solvent through the tank. The solvent is recirculated until the tank is clean at which time it is pumped back into its original storage tank so that it can be reused.