A single sonde locate answers one question: where is the camera now. Tracing a lateral answers a bigger one: where does the pipe go. The route of a lateral across a yard decides where a patio can be built, which tree is the problem, where a repair crew will trench and whether the line really goes to the street or to a tank nobody mentioned. Tracing it is a series of locates joined into a line, and with a camera and a receiver it takes less than an hour for a typical house. This guide covers the method and what to do with the result.
Quick answer: enter at the cleanout and push the head a few feet past the foundation; locate the sonde and mark the point with the counter reading and depth. Push on ten to fifteen feet, locate and mark again, and repeat to the main or the property line, closing the interval where the route turns and at any junction the camera shows. Join the marks with paint or string, photograph the whole route against the house, and sketch it with distances and depths. Use the camera’s picture at each stop to note material changes and defects by distance so the map carries the condition as well as the route.
Why trace the whole line
A repair at one point needs one locate; everything else needs the route. A buyer wants to know whether the lateral runs under the garage slab or the lawn. A landscaper or a pool builder needs the strip that cannot be dug or planted. A repair crew choosing between a spot repair and a liner needs to know how the pipe runs between the two pits. A homeowner installing a cleanout needs the line’s position at the foundation. Inspection before landscaping and before building an ADU are two of the cases.
Setting up
Enter at the cleanout nearest the house or at a pulled toilet, zero the counter at the pipe mouth, and have the receiver, paint or flags, a tape measure and a notebook to hand. Two people make this fast: one on the rod and monitor, one walking the receiver. The two-person workflow covers the division and cleanout entry the setup.
The first locate
Push the head until it is just outside the foundation, a few feet past where the pipe leaves the house, and stop. Locate the sonde from four directions, mark the centre, read the depth and write the counter reading and the depth beside the mark. This first point anchors the route and tells you where the pipe exits the house, which is often not where anyone assumed. Marking a dig covers the locate.
The interval
Push on ten to fifteen feet by the counter and locate again. On a straight run that interval is enough; where the camera picture shows a bend or the receiver’s peak has moved off the line predicted by the previous two marks, halve the interval and locate more often until the turn is defined. Mark each point with the counter reading so the marks can be matched to the footage later.
Junctions and features
Where the camera shows a wye, a tee or a cleanout fitting, stop and locate it; it is a feature worth having on the map and it may be where a branch from another part of the house, an outbuilding or a neighbour joins. Where the material changes, note the distance. Where there is a defect, locate it precisely and mark it in a way that distinguishes it from a route mark, since it is the point a repair will be dug at. The terminology names the features.
Depth along the run
Read depth at each locate and write it down. A lateral falls toward the main, and the depths should increase steadily; a depth that does not fit the trend is a belly or a locate distorted by metal or soil, and both are worth noting. Typical depths, depth limits and metal interference cover the readings.
The end of the run
Continue to the main if the reel reaches it, locating the last point as close to the street as possible, or to the property line where the utility takes over. The camera’s view of the tap is the end of the inspection; the last locate is the end of the map. If the line ends at a tank, a cesspool or anything other than the main, the trace has just found something important. Private lateral responsibility covers the boundary question.
Joining the dots
Paint a line or lay string between the marks, following the curve the points describe, in green for sewer. Photograph the whole route from an upper window or a ladder if possible, and from the street, with the house in frame. The photographs are the map that survives the paint.
The sketch
Draw the house outline and the route on a page, with each locate’s distance from the cleanout and its depth, the features and defects, the material changes and the end point. Add measurements from two or three route points to fixed references such as house corners and the kerb, so the route can be re-established without the camera. This sketch goes in the house file and with the inspection report. What a report should include has a place for it.
Without a camera
A lateral can be traced without a camera by pushing a sonde on a drain cable or by energising tracer wire where it exists; the route is found but the condition is not. Flushable sondes and tracer wire cover those methods, and sonde locating vs line tracing the difference.
Common questions
How do I find where my sewer line runs in the yard?
Push a sonde camera along it and locate the head every ten to fifteen feet from the surface, marking each point, then join the marks.
How long does it take to trace a sewer lateral?
Under an hour for a typical residential lateral with two people, longer alone or where the route turns often.
Why does the depth change along the trace?
The lateral falls toward the main, so depth should increase steadily. A depth that breaks the trend is a belly or a distorted locate; note it.
Related guides
See building lateral basics, measuring lateral length, and how lateral launch cameras work.