Short answer
A truly collapsed section — where the pipe wall has fallen in and the camera cannot pass — cannot be lined; the liner needs a continuous host to take its shape from. But many lines called “collapsed” are partially blocked, offset, or deformed, and those often can be lined after preparation. Where a section really is gone, the choices are a small excavation to replace it and then line the rest, or pipe bursting the whole run.
What “collapsed” actually means
The word gets used for anything a camera cannot pass. Strictly, a collapse is a section where the pipe wall has failed and fallen in: the crown has dropped, soil is in the pipe, and there is no longer a bore for a liner to form against. That is different from a line that is blocked by roots, a line with a severe offset, a line with a broken piece lying in the flow, or Orangeburg that has gone oval. Those all stop a camera, and they all have different answers. So the first step with any "collapsed" verdict is to clear what can be cleared and look again.
Why a liner cannot span a true collapse
A cured-in-place liner is a flexible sleeve until it cures. It is inflated against the host pipe, which gives it its shape and supports it while the resin hardens. Where the host is gone, the liner balloons into the void, cures in that shape or fails to cure evenly, and leaves a weak, misshapen section with unsupported soil above it. Reputable installers will not pull a liner through a void, and a warranty on one that did would not mean much.
What can still be lined after preparation
| Camera finding | Preparation | Then |
|---|---|---|
| Root mass blocking the pipe | Cut and jet | Line if the wall behind it is intact |
| Moderate offset | Grind the ledge | Line |
| Severe offset or dropped section | Excavate and reset that joint | Line the rest |
| Broken piece in the flow, wall intact | Remove with a cutter | Line |
| Crown missing over a short stretch | Spot-replace that stretch | Line the rest |
| Ovalised Orangeburg | — | Replace; not a lining candidate |
| True collapse, soil in the pipe | Spot-replace | Line the rest, or burst the run |
The two real options for a true collapse
Spot repair, then line
The locator marks the collapsed section on the surface. It is excavated, new pipe is set on compacted bedding, and the line is now continuous again. A liner is then installed through the whole run from a cleanout, sealing the joints on either side so the repair is not the only sound part of the line. This is the least disruptive path when the collapse is short and under open ground.
Pipe bursting
Bursting pulls a new HDPE pipe through the old route, breaking the old pipe apart as it goes. It needs a cable through the collapse — usually possible, sometimes with a small pit to pass it — and a pit at each end. It is the better choice when the collapse is one of several problems, when the material is Orangeburg, or when the collapse sits under a driveway or structure where a spot excavation would be large anyway.
Where an open trench still wins
Short, shallow runs under lawn with a collapse near the house; lines where the route needs to move; and lines where the connection at the main has failed and the street end must be opened regardless. In those cases a conventional replacement is not the fallback — it is the simplest correct answer. The trenchless expectations article is candid about that.
What to do with a "collapsed" diagnosis
- Ask for the footage and the distance where the camera stopped.
- Ask whether the line was cleared before the verdict.
- Ask what the surface is at that point, and how deep.
- Ask for the plan to be written as: this section replaced, that section lined or burst, from here to here.
Most lines that are declared collapsed on a first visit turn out to have one bad spot and a lot of lineable pipe. The ones that are truly gone have trenchless answers too. The camera shows which approach fits the line, and how much digging it needs.
Questions people also ask
The camera could not get past 40 feet. Is that a collapse?
Not necessarily. Roots, a heavy offset, a belly full of debris, or a broken piece of pipe lying in the flow all stop a camera. Clearing and a second look usually tells you whether the pipe wall is still there.
Can pipe bursting go through a collapse?
Usually yes, if a cable can be got through the collapsed section. Where it cannot, that spot is opened up, the cable is passed, and bursting continues from there.
What if the collapse is under the house?
Then the choices are opening the slab at that point, or a combination of lining up to the collapse from both sides after a very small opening. The trace decides which is less disruptive.
Does a partial collapse get worse quickly?
It tends to. Once the crown has dropped, soil follows it into the pipe, the void above grows, and the next section loses support. A partial collapse is a scheduling problem; a full one is an emergency.
More of the questions we hear every week are on the FAQ page .
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