Methods and apparatus for monitoring a fluid conduit system for leaks

A fluid conduit system e.g. the hot and cold water system of a domestic dwelling supplied via a main valve 5 from a source 15 is monitored for leaks by a pressure monitor 2 downstream of valve 4 when no fluid is being withdrawn. A shunt valve 6 is proved in a replenishment path across the main valve, both valves 4 and 6 being actuated under the control of control unit 1. The flow rate capacity of the shunt replenishment path is much less than that through main valve 5. After main and shunt valves 4 and 6 are closed and no fluid is being drawn off from the system, the time taken for the pressure to drop to a predetermined value is measured whereupon the shunt valve 6 is opened and the time taken for the pressure to rise to a higher predetermined value is measured. The leakage volume flowrate is calculated from the two time periods and the two pressures together with known constants for the conduit system.