User's Manual

Table Of Contents

Principle of Correlation

In the "classic" correlation process, two sensors are deployed on pipe fittings ("dry"

connection) or connected to hydrants ("wet" connection). The sensors are positioned either

side of the suspected leak position. Noise is created by the leak as it escapes from the pipe

under pressure. This noise is conducted in both directions away from the leak through the

pipe wall (as minute vibrations) and through the water column (as a pressure wave). The leak

noise travels at a constant velocity (V), which depends on the material and diameter of the

pipe, and arrives first at the sensor nearer the leak. The arrival time at each sensor is

registered. The difference (Td) between the two arrival times, combined with knowledge of the

pipe type and length, enables the leak position to be calculated by the correlator. Depending

on the environmental conditions, accuracy of leak pinpointing can be to within centimetres.

Principle of correlation: L = ½ (D-(VxTd))

Leak position

V x Td L L