loudness of a leak heard on an asphalt street or a concrete
slab depends upon the size of the leak, water pressure,
and depth of the pipe. Hard, dry materials like asphalt,
concrete, rock, and compacted soil transmit sounds better
than wet clay, sand, or loose soil. The sounds travel further
on iron and steel pipes than on PVC pipes or Poly pipes.
Before listening on the asphalt or concrete over the
pipe, always listen at hydrants, valves, and meters
within 100 200 ft. of the suspected leak area:
at a hydrant with the magnet base
hydrant, valve or meter is loudest? Leak is closest to
Mark out the locations of the pipes
and listen directly over them:
with the LD-18 directly over the pipe
At the spot no. 1, do you hear the leak? If Yes,
than the LD-18 hears the leak too. Hold the Mute
Switch closed and let the LD-18 listen for
30 60 seconds or longer until the Minimum
Noise Level becomes constant. Press the SAVE
button while still holding the Mute Switch.
Repeat this exact same process for 5 10 spots
directly over the pipe. Spots can be spaced 6 inches
apart or 3 feet apart, but the LD-18 has to be able
to hear the leak.
Each time the SAVE button is pressed (while the
Mute Switch is closed), the Minimum Noise
Level is recorded in the LD-18s memory and a
file number is assigned. Press FILE to see the
File List, and press FILE again to see the GRAPH:
With the Minimum Noise Levels saved at
5 10 spots directly over the pipe, examine
the GRAPH by pressing FILE twice:
Noise Level at each spot is the actual leak sound, and where
it reaches a peak is where the leak is pinpointed.
Band Pass Filters (HI and LO Filters) and Notch Filters (Off,
50 Hz, 60 Hz) are used for removing extraneous continuous
noises like AC hum (60 Hz in USA), motors, air conditioners,
wind, and traffic. Extraneous noises can interfere with the
LD-18s ability to hear the leak sounds.
The Noise Reduction function removes intermittent
noises like footsteps, passing cars, and dogs barking.
Choose Lv.3 (3.0 sec.) to remove the longest lasting
intermittent noises, up to 3.0 seconds long. Intermittent
noises longer than 3.0 seconds cannot be removed.