Product Manual

Figure 4-8 Leak Survey at a Meter
Filtering Out Extraneous Noises
Often there are extraneous noises at a water leak job site, like traffic, wind, AC
hum, etc., that can make leak detection difficult, particularly water leak pinpoint-
ing on the street. The 200 Hz filter or the 400 Hz filter may be effective at reduc-
ing the interference from these extraneous noises.
Step 15 feet away from the water line to an area of the street pavement identical
in surface to that over the water line but without any water lines or other utilities
anywhere beneath it. Listen to the extraneous noises with the ground microphone
on the street, and if it is windy, block the wind's flow around the sensor cable
with your body. Try the 200 Hz filter and listen to whether the extraneous noises
are reduced or eliminated; if not, try the 400 Hz filter. If either filter has reduced
or eliminated the extraneous noises, use that filter and resume leak pinpointing
over the water line.
This method is also very effective when the leak is very small, or very quiet, and
the LD-12 user is not even certain that what he hears is the leak. In this situation,
move 15 feet away from the water line and listen. If you hear the same sounds as
before, then you were not hearing the sounds of a water leak.
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