A pipe stopper assembly includes a stopper fitting defining a fitting channel, the stopper fitting configured to be mounted to a pipeline; and a pipe stopper positioned in the fitting channel and comprising an expandable stopper body and a pressure assembly, the expandable stopper body configurable in an expanded configuration and a contracted configuration, the pressure assembly configurable in an open configuration and a closed configuration; wherein, in the open configuration, the expandable stopper body is biased to the expanded configuration, and in the closed configuration, the expandable stopper body is biased to the contracted configuration; and wherein, in the expanded configuration, fluid is prohibited from flowing through the fitting channel, and in the contracted configuration, fluid is permitted to flow through the fitting channel.