Waste water assessment apparatus, comprising: transceiver circuitry configured to periodically transmit microwave signals through a wall of a closed conduit channelling waste water away from property and for receiving reflections (70, 75, 80) of the microwave signals, from within the closed conduit, that have passed through the wall of the closed conduit; and processing circuitry configured to: process the one or more reflections of the microwave signals to determine a distance between the transceiver circuitry and a surface of the waste water flowing in the closed conduit; determine that the determined distance has been constant for a period of time; distinguish between a constant determined distance corresponding with a steady flow of waste water in the closed conduit and a constant determined distance corresponding with a blockage in the closed conduit by determining that there is a blockage in the closed conduit if the period of time is longer than a threshold period of time; and cause a user to be alerted as to a presence of a blockage in response to the processing circuitry determining that the determined distance between the transceiver circuitry and the surface of the waste water has been constant for the period of time longer than the threshold period of time. transceiver circuitry configured to periodically transmit microwave signals through a wall of a closed conduit channelling waste water away from property and for receiving reflections (70, 75, 80) of the microwave signals, from within the closed conduit, that have passed through the wall of the closed conduit; and processing circuitry configured to: process the one or more reflections of the microwave signals to determine a distance between the transceiver circuitry and a surface of the waste water flowing in the closed conduit; determine that the determined distance has been constant for a period of time; distinguish between a constant determined distance corresponding with a steady flow of waste water in the closed conduit and a constant determined distance corresponding with a blockage in the closed conduit by determining that there is a blockage in the closed conduit if the period of time is longer than a threshold period of time; and cause a user to be alerted as to a presence of a blockage in response to the processing circuitry determining that the determined distance between the transceiver circuitry and the surface of the waste water has been constant for the period of time longer than the threshold period of time. process the one or more reflections of the microwave signals to determine a distance between the transceiver circuitry and a surface of the waste water flowing in the closed conduit; determine that the determined distance has been constant for a period of time; distinguish between a constant determined distance corresponding with a steady flow of waste water in the closed conduit and a constant determined distance corresponding with a blockage in the closed conduit by determining that there is a blockage in the closed conduit if the period of time is longer than a threshold period of time; and cause a user to be alerted as to a presence of a blockage in response to the processing circuitry determining that the determined distance between the transceiver circuitry and the surface of the waste water has been constant for the period of time longer than the threshold period of time.