Heath Consultants Aqua-Scop - Manual (Page 33)

(Figure 18)
The noise of the leak should be checked with the Direct Contact Microphone
at hydrant 4 and at valve 6. Pinpointing with the Ground Microphone will
give a strong noise at point 5. However, at bend points 1, 2, and 3 a high
level of sound may be found.
Please note the effect: Different depths in the cover over the main can give
a varying intensity of the sound. It is always recommended to extend test
areas and not dig at the first strong noise.
(Figure 19)
A restriction or a reducer in the line or a partially closed valve may cause
a false leakage indication. Such cases seldom occur, but you never can
exclude them. Such noises should be checked very carefully and then the
restricted parts of the line should be eliminated if possible.
In checking the main, a leak noise is found at point 1. The next test of the
house connection results in a strong noise at 2. But here a steeply sloped
drain for wastewater is running. To eliminate this condition, the Ground
Microphone is placed at 3 and 4. If the noise at 2, 3, and 4 yield the same
instrument reading, it must be assumed that the drain is causing the sound
and the leakage is at point 1.
30