A solvent storage and depressurization system is described. The system allows a volume of solvent to be stored and used at low pressure, thereby providing safety benefits and regulatory simplicity. The system includes an external expansion tank that is located outside of an extraction facility and that contains a solvent. The system also includes an internal storage tank that is located inside of the extraction facility and that provides a solvent supply to a solvent user, such as a phytochemical extraction system. The external and internal tanks are separated and connected via a duplex manifold. The manifold allows gas below a first pressure level to pass from the external expansion tank to the internal storage tank, and allows gas above a second pressure level to pass from the internal storage tank back to the external expansion tank, wherein the second pressure level is greater than the first pressure level.