What “trenchless” sewer repair does and does not mean

What the word covers

Trenchless is a family of methods that rehabilitate or replace an underground pipe without opening a trench along its length. In residential sewer work that means two things: cured-in-place lining, which builds a new pipe inside the old one, and pipe bursting, which pulls a new pipe through the old route. Both are mature, standardised, and in the right line they are dramatically less disruptive than a trench. That is the whole promise, and it is a real one.

What still gets dug

Bursting pits. One at each end of the run. A few feet square, to pipe depth.
Access where there is no cleanout. Many older Seattle houses have no outside cleanout at all; one is installed, which is a small hole near the foundation and a permanent improvement.
Spot repairs a liner cannot span. A collapsed section, a severe offset, a belly.
Connections. A failed tap at the main, or a shared-line wye, sometimes needs the street or the neighbor's side opened.
Branch reinstatement after bursting. Bursting severs every side connection along the run; each one needs a pit to reconnect.

The only genuinely dig-free scenario is a liner installed from an existing cleanout into a line that is round, continuous and free of bellies. It is common, and it is wonderful when it applies. It does not apply to every line.

When a trench is the right answer

Line	Why open-trench can win
Short and shallow under lawn	A small excavator and a morning; no pits, no liner, new pipe on new bedding
Belly over much of the run	Re-grading is the only fix, and it is a trench by definition
Route needs to change	Trenchless follows the old path; a new path is a trench
Line crowded by other utilities	Bursting displaces soil; a careful trench is safer
Street connection failed	The street end opens regardless; sometimes the rest follows

A contractor who only does trenchless will not offer these. A contractor who only digs will not offer the others. The useful bid comes from someone who does both and shows you the footage that decided it — see what to ask.

How to read a “no dig” promise

Was there a camera first? No footage, no basis for the promise.
Which method? "Trenchless" is not a method. Lining or bursting, from where to where.
Where are the holes? Every bid should list each excavation, its size and its reason — including "none".
What about the belly / the collapse / the connection? If the footage shows one and the bid does not mention it, the bid is incomplete.
What does the warranty say about the dug parts? Spot repairs and connections should be covered the same as the trenchless section.

The fair version of the promise

Many older Seattle side sewers can be fixed from one or two small access points rather than a trench, which can leave most of the yard undisturbed. But the exact number of holes is something the camera tells us, not something anyone should tell you from the curb — and our trenchless page is written on that basis.

Questions people also ask

Is trenchless always better than digging?

Usually less disruptive, not always better. A short, shallow line under lawn with a belly may be less costly and cleaner to trench and re-grade than to burst. The right answer depends on the line, and a contractor with both options can give it.

Why does my trenchless bid include an excavation?

Most likely for a pit, a spot repair a liner cannot handle, or a connection at the main. A good bid says exactly where each hole is, how big, and why.

Can trenchless fix a belly?

No. Lining and bursting both follow the old route, including the sag. A belly needs that section re-graded, which is a dig — usually a small one — and trenchless can then handle the rest.

Does trenchless need a permit?

Yes. Trenchless work on the side sewer is still side sewer work, and Seattle requires a permit and an inspection for it.

More of the questions we hear every week are on the FAQ page .