Repeat this process at 5–10 locations directly above the pipe. The spots may be spaced as close as 6 inches or as far as 3 feet apart, but the LD-18 must still be able to detect the leak.
Pinpoint Water Leaks with the LD-18
1. The loudness of a leak on an asphalt street or concrete slab depends on factors such as leak size, water pressure, and pipe depth. Hard, dense materials like asphalt, concrete, rock, and compacted soil transmit sound more effectively than wet clay, sand, or loose soil. Likewise, leak sounds travel farther through iron and steel pipes than through PVC or polyethylene pipes.
Example 1: Iron Pipe, 75 Psi, 10 GPM Leak, 5 ft. Depth
Example 2: PVC Pipe, 50 Psi, 1 GPM Leak, 3 ft. Depth
2. 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:
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- Listening at a hydrant withe the magnet base
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- Which hydrant, valve or meter is loudest? Leak is closest to the loudest
3. Mark out the locations of the pipes and listen directly over them:
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- Listening with the LD-18 directly over the pipe
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- Mark the spot on the ground
4. At spot no. 1, do you hear the leak? If ‘Yes,’ then the LD-18 hears it as well. Hold the Mute Switch and allow the LD-18 to listen for 30–60 seconds, or longer, until the Minimum Noise Level stabilizes. While still holding the Mute Switch, press the SAVE button.
5. Each time you press the SAVE button (while holding the Mute Switch), the LD-18 records the Minimum Noise Level and assigns it a file number. Press FILE once to view the File List, and press FILE again to display the GRAPH.
6. With the Minimum Noise Levels saved at 5 – 10 spots directly over the pipe, examine the GRAPH by pressing FILE twice:
The Minimum Noise Level at each spot is the actual leak sound, and where it reaches a peak is where the leak is pinpointed.
7. The 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-18’s ability to hear the leak sounds.
8. 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.