810DX 9/9/2008 REV D
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Figure 7-2: Adjacent Utilities - Position of Ground Lead
Move Ground Away From Pipe
7.3 Deep Utility -
Signals picked up by the Receiver from deeply buried utilities are weaker and
not as directionally distinct as those from pipes closer to the surface. In addition, the signal
strength will only change by small increments in relation to moving the Receiver antenna.
Using the Inductive (Indirect) Method of coupling signal to the utility may be difficult if the target
utility is buried 20 feet (6 m) or more. For best results, use the Direct (Conductive) Connection
method.
7.4 Tracing Long Runs -
Signals picked up by the Receiver becomes weaker the farther away
from the Transmitter coupling point, especially on long runs. To get a stronger signal, move the
Transmitter coupling point closer to the Receiver or improve the ground connection. If it is
necessary to use the Inductive mode, the tracing job will be easier if an assistant follows behind
with the Transmitter.
7.5 Locating a Service Lateral -
After tracing the main, go back and locate the service laterals
off the main. Service laterals are easiest to find using the Inductive Mode. Two operators are
required for this procedure. Operator 1 remains stationary holding the Receiver as if to trace the
main. Operator 2 carries the Transmitter, holding it parallel to the main line and maintaining a
minimum of 100 ft. (30 m) between himself and the Receiver. He/she walks parallel to and 5 feet
(1.5 m) from the main on the side he expects to find the service laterals. See Figure 7-3. The
Receiver signal strength will increase as Operator 2 crosses over the service lateral with the
Transmitter. Each time the signal strength increases, Operator 1 signals Operator 2 and marks
the lateral locations on the ground.
7.6 Locating a Bend or Dead End -
While tracing a line, you may find that the signal strength
drops off suddenly, and that there is no distinct reading when the Receiver antenna is moved left
or right. Stand in place and continue sweeping the antenna from side to side but at the same time
slowly pivot your body.
If you find a pivot angle at which the signal strength picks up again, it means you have located a
bend and can resume tracing in the new direction. See Figure 7-4.
If you pivot all the way around (360 degrees), without getting any noticeable signal strength, it
means you have reached a dead end. See Figure 7-5.
7.7 Valves, Manhole Cover, T’s and Risers -
If the signal strength suddenly increases and then
falls back while tracing a pipe you may have probably passed over a buried valve, access cover,
T, or riser.
