To provide a magnetic-disk glass substrate manufacturing method that can reduce the inner diameter dimensional error. In one example, content generated in a first user device is received from the first user device. The system consists of a structure inserted in line with the fixture’s drain, whether directly affixed to the drain or to a pipe leading from the drain. When the acquired distance is equal to or more than the predetermined distance and the destination is a specific point, the determination is based on the end of the route. The height of the compensating reservoir above the tank ensures that the filter is protected from immersion in tank fluid and deaeration is ensured at normal working inclinations of the tank.