Apparatus and method are disclosed for purging a vehicle tank compartment to permit access for repair, or maintenance without environmental pollution or hazard to workmen entering the tank. In accordance with the invention an elongated cylindrical storage tank is tilted about its horizontal axis, to form a reservoir for purge water. The tank is connectable as by flexible hoses to fill and drain connections for a tank compartment of a truck, rail car, or other bulk liquid vehicle. Purge water is pumped from the storage tank at a level above the lower tilted end of the elongated tank and vapor displaced from the tank compartment by the water is recovered through a vapor recovery system. Desirably, the compartment is filled until it overflows into the vapor recovery line. Water is returned to the storage tank at a position near the upwardly tilted end. The tilted arrangement permits gravity separation and accumulation of minor amounts of light hydrocarbons, such as diesel fuel or gasoline at an upper separation zone formed by the upwardly tilted end. A similar separation zone or volume for accumulation of rust particles, sludge and the like is formed at the lower tilted end. Hydrocarbons lighter than water are flushed from the tilted upper end of the reservoir tank by adding water to the reservoir tank so that it overflows through a line connected to a separator tank. Heavy particles from the lower tilted end are removed through a cleanout line entering near the lower tilted end of the reservoir tank. Water may also be removed from the tank to lower the water level at the upper tilted end to increase the surface area of the separation zone for accumulation of such lighter hydrocarbons.
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