Drainage circuit for draining liquid coming from a power plant of a rotorcraft, the circuit incorporating an appliance for monitoring an excessive flow of the liquid

A drainage circuit for passing a flow of a liquid, the circuit comprising at least one upstream duct for collecting the liquid in hydraulic communication with a downstream duct for discharging the liquid to outside the drainage circuit, the drainage circuit being fitted with at least one monitoring device for monitoring an excessive flow of liquid by implementing at least one monitoring appliance having at least one monitoring duct interposed between the upstream duct and the downstream duct and fitted with retaining means for retaining part of the liquid inside a chamber beyond an acceptable threshold for the flow of the liquid through the monitoring duct, the monitoring device including warning means concerning a quantity of liquid captured by the retaining means, wherein the chamber is arranged to receive a spillway of the liquid captured by the retaining means leading to a reserve formed by a container external to the monitoring circuit and fitted with indicator means for visually indicating warning information about the quantity of liquid contained in the reserve.