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SIGNAL
NULL
WITH
LOCATOR
+
AS
SHOWN
1-5/8
Figure
18:
Placement
of
Locator
while
Searching
along
a
Chain
Link
Fence
Locating
Valve
Boxes
Both
the
valve
and
its
casing,
when
iron,
provide
strong
magnetic
fields
that
make
them
easy
to
locate.
Plastic
enclosures
containing
magnets
are
easily
located
at
depths
of
6
feet
or
more.
Figure
19:
Locating
Valve
Boxes
and
Casings
Locating
Cast
‐
Iron
Pipes
As
illustrated
in
Figure
20,
cast
‐
iron
pipes
produce
the
strongest
magnetic
signals
at
their
joints.
+
or
‐
+
or
‐
1
to1
‐
1/2
Feet
Figure
20:
Signal
Patterns
Provided
by
Cast
‐
Iron
Pipes