Intrusion within a Simulated Water Distribution System due to Hydraulic Transients. II: Volumetric Method and Comparison of Results

A pilot-scale test rig was used to simulate intrusion behavior associated with hydraulic transient initiated by rapid valve closure in a water distribution system. In Part I, the test rig apparatus and operating conditions were described and intrusion volumes were reported based on a chemical tracer and mass balance calculations. In this paper, the experimental study is extended to determine intrusion volumes by a volumetric method that used video recordings of water fluctuations in the observation column. The results obtained using the volumetric and chemical tracer methods were compared to theoretical calculations. Intrusion volumes associated with a 12.7-mm (1/2-in.) diam orifice were evaluated in addition to 3.2 (1/8-in.) and 6.4-mm (1/4-in.) orifices. The impact of the external head on the intrusion volume was also assessed by comparing results using 0.91 (3 ft) versus 1.37 m (4.5 ft) of external head. The average intrusion volumes obtained using the volumetric approach ranged from 47.3 to 550.2 mL. These volumes were 64–298% greater than intrusion volumes determined by the chemical tracer method reported in Part I. However, the theoretical calculations indicate that the volumetric approach could underestimate intrusion volumes by as much as 50%.