A PVC or HDPE sewer lateral carries no current and reflects no radio, so once it is buried the only way to find it from the surface is to push a sonde along it or to dig. Tracer wire solves that: an insulated copper or copper-clad steel conductor laid in the trench beside the pipe, brought to the surface at a cleanout or an access box, and left there so a locator can energise it years later and follow the pipe’s route. Many codes now require it on new plastic laterals. This guide covers what it is, how to use it and why it so often does not work when it is needed.
Quick answer: tracer wire is a buried conductor that follows the pipe and ends at an accessible terminal, usually at the cleanout riser or a small ground box. To trace the pipe, clip a line-tracing transmitter’s lead to the wire’s end and its ground lead to a stake, select a frequency, and follow the energised wire with the receiver in line mode, marking the route and reading depth. It fails when the wire was never installed, was broken during backfill or later digging, has corroded at a splice or a terminal, or was never brought to the surface. Test it with a continuity check before relying on it.
What tracer wire is
Insulated solid copper, typically 10 to 14 gauge, or copper-clad steel for strength, with a thick jacket rated for direct burial. Green is the conventional colour for sewer tracer wire. It is laid in the trench on or beside the pipe, taped to it at intervals so it stays with the pipe, and continued to an access point. Splices are made with waterproof connectors rated for burial; a twisted and taped splice corrodes within a few years. The marking colour code uses green for sewer in the same way.
Where it is required
Codes and utility standards increasingly require tracer wire on non-metallic laterals, and many municipalities require it for any new sewer connection. Older plastic laterals mostly have none. Where a lateral was installed in the last decade or two under a permit, a wire may exist; where it was installed earlier or without a permit, assume not. Permits and inspections cover where the requirement is checked.
Finding the end
The wire should terminate at the cleanout riser, taped or clipped to it just below the cap, or in a small access box at grade near the foundation or the property line. Look inside the cleanout riser and around its base. If the wire was never brought up, it may be found with a passive sweep in radio mode if it is long enough, or not at all. Cleanout access covers finding the riser.
Testing it
Before tracing, check that the wire is continuous. If both ends are accessible, a multimeter across them shows continuity. If only one end is accessible, a transmitter connected to it and a receiver walked along the expected route show where the signal stops, which is where the wire is broken or ends. A wire that reads open at the terminal is broken somewhere and will trace only to the break.
Energising and tracing
Clip the transmitter’s signal lead to the bare end of the wire and its ground lead to a stake pushed into damp soil a few metres away, at right angles to the expected route. Select a low or medium frequency for a long run, since low frequencies travel further and bleed less onto neighbouring conductors. Set the receiver to the same frequency in line mode and walk from the terminal along the peak, marking the route every few feet and reading depth where it matters. Sonde locating vs line tracing covers the technique and multi-frequency locators the frequency choice.
What a trace tells you
The route of the wire, which is the route of the pipe if the wire was taped to it. The depth of the wire, which is close to the pipe’s depth. Where the wire ends or breaks. It does not show the pipe’s condition, joints or defects, which need the camera. A trace before the camera inspection tells the inspector where the line goes; the camera then tells them what it is like. Tracing a lateral across a yard covers combining the two.
Why tracer wire fails
Never installed, despite the requirement. Broken by the backfill machine or by a later landscaper. Corroded through at a splice made with the wrong connector. Terminal corroded or buried under a new patio. Pulled off the pipe during installation so it traces a route the pipe does not follow. A wire that fails any test is a wire that cannot be trusted, and the sonde in the camera becomes the route-finding tool. Locating the camera underground is the fallback.
Installing it properly
For anyone laying a new lateral: use burial-rated wire, tape it to the pipe every few feet, make every splice with a waterproof direct-burial connector, bring it up at the cleanout and leave a foot of slack, and terminate it in a way that leaves bare copper accessible under the cap. Test continuity before backfill and again after. Record it on the as-built. A wire installed this way is found in thirty years.
Tracer wire and the sonde
A lateral with working tracer wire can be traced in minutes without a camera; a lateral without it needs the sonde pushed along and located at intervals. Both give the route. The wire is faster and does not need pipe access; the sonde also gives a camera picture. An inspector with both uses the wire to plan and the sonde to confirm. Locator compatibility covers receivers that do both jobs.
Common questions
What is tracer wire on a sewer line?
An insulated conductor buried alongside a plastic pipe and brought to the surface so a locator can energise it later and follow the pipe’s route.
How do I find the end of the tracer wire?
Inside or beside the cleanout riser, or in a small access box near the foundation. If it was never brought up, it may not be findable.
Can a 512 Hz sewer camera locator trace tracer wire?
Only if the receiver has line-tracing frequencies and a matching transmitter. A sonde-only receiver cannot energise a wire.
Related guides
See building lateral basics, how to use a sewer camera, and the camera head sizes guide.