A method for using a monitoring system to maintain a volume of reprocessing fluid within a supply reservoir for a fluid circulation system (290a, 290b) of an instrument reprocessor (100), said method comprising the steps of : supplying a quantity of reprocessing fluid to the supply tank (220) from a source of reprocessing fluid (201a, 201b)； detect the amount of reprocessing fluid in the supply tank； determining whether the amount of reprocessing fluid in the supply tank is more than a predetermined amount； operate a positive displacement filling pump (210) to supply reprocessing fluid to the supply tank (220) if the amount of reprocessing fluid in the supply tank is less than a predetermined amount, where the displacement filling pump positive (210) is configured to supply a fixed volume of reprocessing fluid per stroke； monitor the amount of reprocessing fluid in the supply tank (220) as the positive displacement filling pump (210) is being operated； determining whether the amount of reprocessing fluid in the fluid reservoir (220) has increased by a re-supply volume equal to the product of the volume displaced per stroke and the number of strokes of the positive displacement filling pump (210)； and issue an alert if the amount of reprocessing fluid in the supply tank (220) has not increased by the volume of re-supply.Un método para utilizar un sistema de monitorización para mantener un volumen de fluido de reprocesamiento dentro de un depósito de suministro para un sistema de circulación de fluido (290a, 290b) de 5 un reprocesador de instrumentos (100), dicho método comprendiendo los pasos de: suministrar una cantidad de fluido de reprocesamiento al depósito de suministro (220) desde una fuente de fluido de reprocesamiento (201a, 201b)； detectar la cantidad de fluido de reprocesamiento en el depósito de suministro； determinar si la cantidad de de fluido de reprocesamiento en el depósito de suministro es más que una cantidad predeterminada； accionar una bomba de ll
