Line Locating Reference

Line Locate Field Guide

Quick reference guide for line locating methods, utility marking codes, and field best practices. Know your approach before you dig.

Direct Connect
Best accuracy - direct connection to target line

Best For:

Metallic water lines
Gas pipes
Metal conduit
Direct access to line

Procedure:

  1. 1.Connect transmitter directly to exposed metallic line
  2. 2.Ensure good ground connection at least 10 ft away
  3. 3.Set appropriate frequency (512 Hz, 8 kHz, or 33 kHz)
  4. 4.Walk the line with receiver, following the strongest signal
  5. 5.Mark location and depth at regular intervals

💡Pro Tips:

  • •Clean connection points for best signal transfer
  • •Verify signal strength before starting trace
  • •Watch for signal bleeding to parallel utilities
  • •Use lower frequencies for deeper or longer runs
Inductive Clamp
Non-invasive signal induction onto metallic lines

Best For:

Live electrical cables
Gas lines without access
Water mains through meter
Bundled utilities

Procedure:

  1. 1.Clamp transmitter around target conductor
  2. 2.Position clamp at known access point (meter, panel, etc.)
  3. 3.Orient clamp for maximum signal coupling
  4. 4.Set receiver to matching frequency
  5. 5.Follow signal, noting depth and position

💡Pro Tips:

  • •Ensure clamp jaws are fully closed and clean
  • •May need to isolate target from parallel lines
  • •Works best on single conductors
  • •Higher frequencies for shorter, shallower runs
Induction (Broadcast)
Signal broadcast for general area scanning

Best For:

Exploratory surveys
Unknown utility locations
Multiple parallel lines
Quick scanning

Procedure:

  1. 1.Place transmitter on ground in vertical position
  2. 2.Set to active induction mode
  3. 3.Broadcast signal covers circular area
  4. 4.Scan with receiver in all directions
  5. 5.Identify and mark all detected utilities

💡Pro Tips:

  • •Signal induces on all nearby conductors
  • •Less precise than direct methods
  • •Good for initial survey work
  • •Mark everything found before detailed tracing
Sonde (Beacon)
Self-contained beacon for non-metallic lines

Best For:

Sewer camera heads
Push rods in PVC/PEX
Drain snakes
Non-conductive pipes

Procedure:

  1. 1.Attach sonde to camera head or push rod
  2. 2.Insert into target pipe/conduit
  3. 3.Sonde broadcasts its own signal
  4. 4.Use receiver in sonde mode
  5. 5.Mark sonde position and depth at intervals

💡Pro Tips:

  • •Different frequencies for different depths
  • •512 Hz for deep locations (up to 20 ft)
  • •Higher frequencies for shallow work
  • •Battery life is critical - check before use
Passive Mode
Detect existing signals on energized lines

Best For:

Live power lines
Radio frequency detection
Cathodic protection
Quick confirmation

Procedure:

  1. 1.Set receiver to passive mode (no transmitter needed)
  2. 2.Select frequency (50/60 Hz for power)
  3. 3.Scan area for ambient signals
  4. 4.Identify power, radio, and other active signals
  5. 5.Confirm with active tracing if needed

💡Pro Tips:

  • •Good for finding live electrical cables
  • •50/60 Hz power mode most common
  • •Radio mode detects cathodic protection
  • •Can't provide accurate depth info
  • •Always verify with other methods