Trenchless Sewer

Pipe Bursting

The whole line replaced without opening the yard. A bursting head fractures the old pipe outward and pulls fused HDPE in behind it in one pass.

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You have probably already seen the footage, and it is a specific kind of bad. The picture goes oval instead of round, or the camera head noses into something and simply will not pass, and whoever was holding the reel stopped narrating. An unmistakable oval or egg-shaped bore. Blistering and peeling of the inner wall. Often the camera simply cannot pass. That is the pipe this method exists for. There is nothing left in the ground worth saving and nothing structural to build against, so the question of whether to repair or replace answered itself before anybody quoted anything.

What bursting does with that is counter-intuitive the first time it is explained. A bursting head is pulled through the old pipe on a cable. It fractures the existing line outward into the surrounding soil and drags a new fused HDPE pipe in behind it in the same pass. The old line is not removed — it becomes part of the ground the new one sits in. You do not get the old pipe back in a skip. You get a new one occupying the same corridor, in one continuous length, with no joints buried anywhere between the two pits. The new line is HDPE: Nothing age-related in ordinary service. It does not corrode, it does not scale, and because a pulled-in run has no joints in the ground there is nothing for a root to enter. That is the whole return on the job — not a repaired sewer, but a line with nothing in it for a root to find.

Is pipe bursting cheaper than trenching? Usually, and rarely because of the pipe work itself. The two jobs put a similar new line in the ground; what separates them is everything above it. It takes out whatever is above the line — lawn, driveway, patio, mature tree roots — and reinstatement is often the largest part of the cost. Burst the same run and that cost mostly disappears, which is why the method wins under driveways, patios and mature trees and loses on a short shallow run through open lawn.

How pipe bursting runs, step by step

  1. Step 1

    Confirm it is a bursting job

    Bursting replaces everything. If the camera shows one bad joint in sound pipe, this is the wrong service and we will say so.

  2. Step 2

    Clearance along the run

    The ground is displaced outward as the head passes, so what else is buried near the line has to be established before anything is pulled.

  3. Step 3

    Two pits

    One at each end of the run. Between them the driveway, the trees and the patio are not touched — that is the entire reason for the method.

  4. Step 4

    Pull through

    The head is winched up the old line, fracturing it outward into the soil and dragging the new HDPE pipe in on the same cable.

  5. Step 5

    Reconnect and verify

    Connections re-established at both ends, any severed branch re-tied, and the finished line put back on camera.

What the day actually looks like

The first thing that surprises people is the new pipe lying in the street. It arrives as one continuous length, so before anything goes underground it has to be somewhere above ground, laid out along the run or up the block, and on a tight inner-city lot that is a genuine logistics problem rather than a detail. The second surprise is how much of the day is pits. Digging, shoring and setting up the two access holes is most of the visible work, and the pull itself — the part everybody wants to watch — is short, slow and almost boring to look at.

During the pull there is steady pressure on a cable and very little to see. Ground directly over the line can lift or settle slightly as the head passes, which is expected rather than alarming, and it is the reason clearance from whatever else is buried nearby gets established before anybody rigs anything. Afterwards both ends are tied in, anything the burst severed is re-established, and the finished line goes back on camera end to end so you watch the new bore rather than take our word for it. Two pits rather than an open trench across the yard. Driveways, mature trees, patios and fences between the pits are generally left alone, which is usually the entire reason the method is chosen.

What decides the scope

Length and depth set the shape of the job: a longer run is more pipe and more pull, but depth is the driver people underestimate, because a deep pit is a bigger, shored, more slowly dug hole at both ends. Then the host material, which decides whether the method is available at all. Vitrified clay bursts predictably. Cast iron bursts. Concrete is a case-by-case answer rather than an assumption — it is tougher and less predictable about how it fragments. ABS and Orangeburg both burst, and in the case of Orangeburg it is very often the only method left.

The rest is what surrounds the line rather than the line itself. It displaces soil sideways. Where another utility runs close and parallel, that has to be established by locates before anything is pulled, and sometimes the answer is that it cannot be done safely. Anything joining the run partway along has to be found before the pull and re-established after it. Surface matters in both directions: what is above the pits has to come up and go back, while what is between them — the driveway, the fence posts, the elm that was planted when the street was — is precisely what is being bought. And access decides feasibility outright, because a rig and two open pits need somewhere to stand on a narrow lot with lane access only.

What people get wrong about this

The old pipe stays down there

People expect a replacement to mean removal, and it does not. The fractured clay or fibre is pushed out into the surrounding soil and stays in the ground as part of the bedding the new line sits in. Nothing is trucked away except the spoil from the two pits.

A severed branch is a separate job

Existing connections along the run — a branch from a second building, a garage drain — are severed by the burst and have to be re-established separately. A garage floor drain, a laundry line from an old addition, a second building on the same lot — if one exists it needs to be identified on camera beforehand, because it is far cheaper to plan for than to discover.

It cannot move the line or fix the fall

It cannot correct a line that is in the wrong place or at the wrong grade — the new pipe follows the path of the old one. If the existing run has a belly in it, or was laid at the wrong grade, or sits under something it should never have been put under, bursting faithfully reproduces that decision in new pipe. Those are dig jobs and there is no way around it.

The locates can end the conversation

Because the ground is displaced outward as the head goes through, something running close and parallel to the line can make the pull unsafe. Occasionally the honest answer after locates come back is that this particular run cannot be burst, and the alternative is excavation rather than a different trenchless method.

When this is the wrong answer

Bursting replaces everything, so it is the wrong answer whenever the problem is somewhere rather than everywhere. A line with one defect and sound pipe either side of it — that is a spot repair or a lining job, and bursting the whole run is buying far more than the problem requires. A single cracked or offset joint in otherwise sound pipe is what spot repair is for: One crack, one offset joint, or one root intrusion in an otherwise sound line. A structurally sound line that leaks at the joints is a lining job: A structurally sound but leaking pipe — the classic case being clay with root intrusion at the joints and good pipe in between. And where the run is short, shallow, under bare ground and the ground either side of it is already disturbed, digging is simply the cheaper mobilisation and we will tell you that rather than sell you a pull.

The method itself, including what it cannot do

Every method we use is defined in one place, so the page describing it and the page comparing it cannot disagree. The limitations below are part of that definition, not a disclaimer attached to it.

Pipe bursting

Also called static bursting, pneumatic bursting, trenchless replacement

A bursting head is pulled through the old pipe on a cable. It fractures the existing line outward into the surrounding soil and drags a new fused HDPE pipe in behind it in the same pass. The old line is not removed — it becomes part of the ground the new one sits in.

What it needs from the existing line

  • Two access pits, one at each end of the run — typically one at the house and one at the property line or the connection.
  • A path the head can follow. Severe offsets can stop it.
  • Enough clearance from other buried utilities along the run, because the ground is displaced outward as the head passes.

What it cannot do

  • It displaces soil sideways. Where another utility runs close and parallel, that has to be established by locates before anything is pulled, and sometimes the answer is that it cannot be done safely.
  • It cannot correct a line that is in the wrong place or at the wrong grade — the new pipe follows the path of the old one.
  • Two pits still have to be dug. This is trenchless, not excavation-free, and the pits are real holes in real ground.
  • Existing connections along the run — a branch from a second building, a garage drain — are severed by the burst and have to be re-established separately.
What the property looks like
Two pits rather than an open trench across the yard. Driveways, mature trees, patios and fences between the pits are generally left alone, which is usually the entire reason the method is chosen.
Right when
A line that is failing along its whole length, or one too deformed or collapsed to line.
Wrong when
A line with one defect and sound pipe either side of it — that is a spot repair or a lining job, and bursting the whole run is buying far more than the problem requires.

Side by side with the alternatives, and when the answer is a dig →

A pipe bursting head attached to new black HDPE sewer pipe in an access pit, beside broken pieces of the old clay pipe.
A bursting head and new HDPE pipe in the access pit

People also ask

Is pipe bursting cheaper than trenching?

Often, and sometimes emphatically not. Compare the restored property, not the pipe work: trenching is priced by what has to be put back. Over a driveway or a mature tree, bursting usually wins. Over a short, shallow run under bare lawn, digging is frequently the cheaper finished job.

Questions about pipe bursting

The ones that come up on this work specifically. The general questions are answered on the FAQ page.

Can bursting be done under a driveway or a mature tree?
That is the case the method exists for. The head is pulled through the old line from a pit at each end, so whatever sits between those two pits — concrete, hardscape, a root plate that took forty years to grow — is never opened. It is also where the cost comparison usually settles in its favour, because trenching is priced by what has to be put back rather than by the pipe. One note on trees in the older parts of this city: a boulevard tree may not be yours to make decisions about, and that is a question for the City before it is a question for a contractor.
What happens to the old pipe?
It stays in the ground. The bursting head fractures it outward into the surrounding soil and the new fused pipe is drawn in behind it through the space that creates. Nothing is hauled away and no disposal appears on the invoice — which surprises people, so it is worth saying before the work rather than after. What goes in is HDPE, joined by heat fusion, so between the two pits there are no joints in the ground at all. On a clay lateral that had a joint every few feet, removing the joints removes the thing that failed.
What would stop you from bursting a line?
Three things, and all of them get established before anything is pulled. A path the head cannot follow — severe offsets can stop it. Clearance from other buried services, because the method displaces soil sideways, so where something runs close and parallel along the run the locates decide it and sometimes the answer that comes back is that it cannot be done safely. And a line that has to change grade or route, because the new pipe follows the path of the old one exactly. Any of those three and the conversation turns to digging.
What happens to a branch that joins the line partway along?
It is severed by the burst and has to be re-established separately. A branch from a second building, a garage drain, a connection to an addition — anything joining the run between the two pits is in the path of the head. This is real work with its own time and its own line on the quote, and it should appear there. If your line has a branch and the quote does not mention it, the quote is incomplete. Walk the property with whoever is pricing it and point out anything that drains.

Also asked on every job

Answered in full, once, on the page each one belongs to — rather than repeated on every page of this site.

Every question we are asked, and where each is answered

Nothing is quoted off a description

The camera goes down first and you keep the footage. If the answer is that there is nothing wrong with your line, that is what you will be told.

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