Experimental evidence of backflow phenomenon in a pressurized pipe

According to a recent survey [1], approximately 20% of the waterborne illnesses between 1971 and 1998 must be attributed to distribution system deficiencies, e.g., backflow at connections, pathogen entry along buried infrastructure during period of low pressure. As an example, non-potable water can be drawn into distribution systems during transients, if a pathway exists and the pressure in the pipe system is lower than the external one. This paper shows an intrusion process through a leak in a laboratory pipe during a transient event. The leak discharges into an external constant level tank that simulates an aquifer (a possible source of potential threat to public health). To provide a simultaneous overview of the kinematics of the unsteady-state flow field, simultaneous measurements of instantaneous velocity profiles and pressure are carried out in the most attractive sections of the system.