Product Manual

4-5
Distances transmitted for the sounds of water leaks are a function of the pipe
diameter as well as the pipe material (see table below).
Pipe Material and Diameter Typical Max. Distance for
Transmission of Leak Sounds
6 inch Cast Iron Pipe 600 to 1000 feet
12 inch Cast Iron Pipe 400 to 800 feet
24 inch Cast Iron Pipe 200 to 400 feet
6 inch AC Pipe 400 to 800 feet
12 inch AC Pipe 300 to 500 feet
24 inch AC Pipe 100 to 300 feet
6 inch PVC Pipe 200 to 300 feet
12 inch PVC Pipe 100 to 200 feet
24 inch PVC Pipe 50 to 100 feet
Thus knowledge of the pipe material and diameter is important to knowing how
far the sounds of a leak may be transmitted along the pipe walls. If the leak is in
a 6 inch cast iron water line, the LD-12 user will listen first at the hydrants and
main valves. If the LD-12 user hears nothing at the first location, he moves 500
to 600 feet to another hydrant or main valve. If the leak is in a 24 inch PVC pipe
however, the LD-12 user cannot simply listen at only hydrants and main valves
and be assured that there are no leaks within 500 to 600 feet. In this case, the LD-
12 user must check at every possible curb stop and valve, or the user may even
“ground mike” the entire length of the 24 inch PVC pipe.
Water Leak Surveys
If there is no obvious evidence of a major water leak, like water surfacing or very
loud leak sounds at the hydrants, but the area is experiencing abnormally large
water losses, then a "water leak survey" may be needed. The water leak survey is
usually done with only the magnet base attached to the sensor, and it initially is
conducted only at the hydrants and the main valves (see Figure 4-6).