The disclosed invention relates to detecting a flow condition in a fluid supply system. The invention is particularly useful for detecting flow in a toilet system. The flow detection device comprises a processor associated with a flow sensor. Predefined flow criteria are stored in a memory associated with said processor. When the processor detects flow through the fluid supply system, the processor uses the flow criteria to characterize the detected flow. If such flow complies with predefined flow conditions, a flow event is noted and an alert is issue. Such alert is configured according to predefined alert-criteria stored in a memory.