Improved Model for Contaminant Intrusion Induced by Negative Pressure Events in Water Distribution Systems

Untreated water can intrude into water distribution systems through pipe cracks and/or openings when negative pressure events occur inside drinking water pipelines. It is important to determine the magnitude of the possible intrusion event. To estimate the intrusion flow rate more accurately, the effects of surrounding soil must be considered. In this paper, an analytical relationship is derived by combining the seepage in soil and the flow through an orifice for predicting the intrusion flow rate for a circular orifice under steady-state conditions. The effect of the pipeline on reducing the flow area is incorporated in the model. An experimental study that simulates a buried pipeline was carried out to validate the accuracy of the improved model, and the analytical results fit well with the experimental results.