A method for controlling false alarms in defect detection for water pipelines

Measurement noise and modeling uncertainties often cause false alarms when inverse wave-scattering methods are applied to detect defects in urban water supply systems, particularly when identifying incipient defects on the millimeter- to centimeter-scale in pressurized pipelines. Such false alarms undermine detection reliability, erode confidence in wave-based diagnostics, and increase operational costs. This study proposes a general false-alarm control method that can be integrated into existing inverse algorithms without requiring prior knowledge of the pipe condition. The method defines a decision threshold γ(p) corresponding to a user-specified false-alarm probability p and employs a bootstrap procedure to estimate γ(p) under small-sample conditions typical of field measurements. The method is specifically evaluated for incipient defect detection using high-frequency acoustic waves with wavelengths comparable to the pipe diameter. Numerical simulations and laboratory experiments on high-density polyethylene pipes confirm that the proposed method maintains the specified false-alarm probability even at a signal-to-noise ratio of 0 dB, accurately distinguishing false alarms and detecting true blockages as small as 5 mm in thickness and 11 cm in length within a 39.3 mm-radius pipe, using as few as ten measurements.