Failures and leaks are normally modelled separately, with failure models used to prioritise pipes for refurbishment or estimate remaining service life, and leak models to estimate leakage flow rates. In this study, a conceptual model for the combined development of pipe failures and their leakage rates over time is proposed. The model includes different phases of the failure development process, from the initiation of a weak point in the pipe wall to leak discovery and repair.
The conceptual model was calibrated on the observed impact of time and pressure on pipe failure rates in the city of Auckland, New Zealand. It was then used to predict the impact of pressure management on the failure rate of a typical pressure zone over time. The results show a pronounced drop in the failure rate on implementation of pressure management, which correspond to observations from the field. However, the model then predicts that the reduced failure rate will only be sustained for a certain period. After this period, the leakage rate will increase again to approximately pre pressure management levels, but still significantly lower than it would have been without it. Further work is required to verify the model predictions against field data.
