Trenchless Sewer Repair: How It Works and When It Does Not

What is trenchless sewer repair, and what are the two methods?

Trenchless sewer repair uses the old pipe as the route for the new one. Instead of a trench the full length of the lateral, the crew works from a pit at each end, sometimes from an existing cleanout.

Pipe bursting pulls a cone shaped head through the old line on a steel cable. The head splits the clay or cast iron outward into the soil and drags a new HDPE pipe in right behind it. What you end up with is fused plastic with no joints, so there is nothing left for roots to pry open. CIPP lining, short for cured in place pipe, pushes a resin soaked tube into the old pipe, inflates it tight against the wall, and cures the resin hard. The old pipe stays in the ground as a shell and the liner becomes the working pipe.

A federal fact sheet on pipe bursting puts it at 4 to 24 inch pipe with a practical pull of about 750 feet, far more than any house lateral needs, and notes the head typically moves about 100 feet an hour. Read the EPA fact sheet on pipe bursting.

What does the camera inspection decide?

The camera picks the method. Anybody quoting you trenchless work without putting a camera down the pipe first is guessing. A camera run costs $150 to $500 in our price list, less when there is already a cleanout. What the operator is reading:

• Pipe material. Clay and cast iron burst cleanly. Ductile iron and short steel repair couplings do not, and one hidden coupling can stop a pull cold.
• Standing water. Water sitting in a low spot that never drains means the pipe has lost its fall. That is a belly.
• Joint condition. A hairline crack or a slightly shifted joint is lineable. A joint where the pipe ends have walked far enough apart to catch the camera head is not.
• Depth and route. Pit locations come off this, and so does whether street work needs an encroachment permit.

Ask for the footage. You paid for it, and a contractor who will not hand over the video has told you something.

What happens on install day?

A bursting job runs in the order the federal guidance lays out: run the camera, keep flow out of the line, dig the access pits, disconnect the services, cut out anything in the way, burst and pull the new pipe, pressure test it, tie it in, then reconnect and backfill. Most of the day goes to the pits and the tie ins, not the pull.

A lining job starts differently. The pipe gets jetted clean first, because resin will not bond to a wall packed with grease and root hair. Then the crew measures the run, wets out the liner, inverts it under pressure, and holds it inflated while it cures. Nothing drains through that line until the resin is hard, so curing is the part nobody rushes. After it sets, the crew reopens any branch connections and runs a final camera pass.

In our experience a residential lateral is a one day job either way. It stretches to two when there is concrete to cut and put back, or when the work crosses into the street and the city wants traffic control.

When does trenchless sewer repair not work?

Four things rule it out.

A collapsed section. Both methods need a continuous path. Bursting needs a cable through the pipe, and the EPA guidance lists a collapsed pipe as a known difficulty. A liner needs a wall to press against, and a crushed section has none.

A belly. Neither method moves the pipe. Bursting follows the old alignment and a liner copies it exactly, so a line that sags keeps sagging, with a new pipe holding the same puddle. Fixing fall means excavating and resetting the bedding.

A badly offset joint. Lining handles cracks and modest offsets fine, one of its strengths. Once the ends are far enough out of line that a camera head catches on the lip, a liner wrinkles or tears there instead of sealing.

Ground that will not cooperate. The same guidance flags soil below the water table, other utilities within a couple of pipe diameters, and shallow pipe where the bursting head can heave the pavement above it. A shallow line under a patio is a real case for lining instead.

Does a CIPP liner make the pipe smaller?

Yes. Perma-Liner, a common small diameter lateral system, specifies a 3 mm liner for pipe in the 2 to 8 inch range and runs continuous lengths past 120 feet on 4 inch work. See the manufacturer specification. Three millimeters of wall on each side takes roughly a quarter inch off the inside of a 4 inch pipe.

What you get back is a smooth, jointless bore. The EPA guidance makes the same point: lining cuts the diameter and with it the hydraulic capacity, but the new surface is less rough than the old pipe, which gives some of it back. On a 60 year old clay lateral furred with root hair and scale, a thin liner can move water better than what it replaced. Bursting gains capacity outright, since the new pipe goes in the same size or one size up.

Which method should you pick?

Lining wins on a sound lateral with cracks, open joints, and roots, especially a shallow one under hardscape. Bursting wins when the pipe material is finished everywhere, when you want full diameter or a size up, and when there is room for a pit at each end. Open trench wins on a belly or a collapse, because grade is the one thing trenchless cannot fix.

Per foot pricing, hardscape savings, and permit figures are in our sewer line replacement cost guide. Marin sellers have a separate hurdle, since several districts require a passing lateral inspection at the point of sale, and those rules are in our guide to Marin sewer lateral inspections.

Before you sign, ask which defect decided the method, whether a post job camera pass is included, and who restores the pits and the concrete.

CNTRline has worked Sonoma and Marin sewer laterals since 2017, CSLB #1036920. We run the camera, pull the permit, and hand you the video and a written price before anybody digs. Call (707) 308-5599 for a free quote on sewer line repair. Not sure the lateral is the problem? Start with a main drain that is backing up.