A system for adjusting the output pressure of a pressure reducing valve supplying fluid to a consumer region, comprising a controller having: a control output for providing a signal to adjust the output pressure of the pressure reducing valve; data storage means storing parameters representing a required output pressure from the pressure reducing valve in order to establish a desired minimum fluid pressure at a critical point in the consumer region in accordance with a measured value; processing means configured to process (i) data representative of the measured value and (ii) the stored parameters, so that a signal is provided from the control output in order to cause the pressure reducing valve to be adjusted to provide the required output pressure corresponding to the measured value; a pressure input for receiving an output pressure signal from an output, pressure sensor and means adapted to provide data representative of the output pressure from the pressure reducing valve; characterised in that: the controller comprises logging means to log data including data representative of the output pressure from the pressure reducing valve, with time stamp data; the controller further comprises a communications module; the system further comprises a remote data processing system; the controller is configured to use the communications module at intervals to communicate logged data to the remote data processing system; the controller is configured to use the communications module at intervals to receive parameter data from the remote data processing system; the remote data processing system is configured to receive the logged data from the controller and to transmit the parameter data to the controller at intervals; the remote data processing system is further configured to receive critical point pressure data from a critical point pressure sensor (10, P3) adjacent the critical point, the critical point pressure data including time stamp data; and the remote data processing system is further configured to calculate the parameter data to be transmitted to the controller using the logged data received from the controller and the critical point pressure data. a control output for providing a signal to adjust the output pressure of the pressure reducing valve; data storage means storing parameters representing a required output pressure from the pressure reducing valve in order to establish a desired minimum fluid pressure at a critical point in the consumer region in accordance with a measured value; processing means configured to process (i) data representative of the measured value and (ii) the stored parameters, so that a signal is provided from the control output in order to cause the pressure reducing valve to be adjusted to provide the required output pressure corresponding to the measured value; a pressure input for receiving an output pressure signal from an output, pressure sensor and means adapted to provide data representative of the output pressure from the pressure reducing valve; the controller comprises logging means to log data including data representative of the output pressure from the pressure reducing valve, with time stamp data; the controller further comprises a communications module; the system further comprises a remote data processing system; the controller is configured to use the communications module at intervals to communicate logged data to the remote data processing system; the controller is configured to use the communications module at intervals to receive parameter data from the remote data processing system; the remote data processing system is configured to receive the logged data from the controller and to transmit the parameter data to the controller at intervals; the remote data processing system is further configured to receive critical point pressure data from a critical point pressure sensor (10, P3) adjacent the critical point, the critical point pressure data including time stamp data; and the remote data processing system is further configured to calculate the parameter data to be transmitted to the controller using the logged data received from the controller and the critical point pressure data.