Pipe bursting glossary

A–ZTerms

As-built drawing

A record drawing marked up after construction to show where the new pipe, pits, connections and any rerouted utilities actually ended up.

Asbestos-cement pipe

A brittle pipe of cement reinforced with asbestos fibre, used for some older water mains and sewers. It bursts readily, but exposed pieces at pits need asbestos precautions.

Belly

Another word for a sag: a low section of pipe that holds water and solids. Bursting generally reproduces it unless it is corrected first.

Bend radius

How tightly a pipe can curve without damage. HDPE can be cold bent to roughly 25 to 30 times its outside diameter, which sets the length of a launch pit's slope.

Building drain

The pipe inside or under the house that collects waste from the plumbing and carries it out through the foundation to the lateral.

Bursting head

The hardened cone pulled through the old pipe. Its nose follows the host pipe and its widest part, the expander, breaks the pipe and pushes it into the soil.

Butt fusion

Joining two polyethylene pipe ends by facing them square, heating them on a plate and pressing them together until they cool into one piece.

Bypass pumping

Temporarily pumping sewage or supplying water around the section being replaced so the system keeps working during the burst.

CCTV inspection

A closed-circuit camera run through a pipe, recorded with distances. It is the starting point for any bursting plan and the proof at the end.

CIPP (cured-in-place pipe)

A lining method in which a resin-soaked tube is placed inside the old pipe and hardened there. It keeps the host and slightly reduces the bore.

Collapse

A section of pipe that has caved in. If a cable or rod cannot pass it, a pit is needed at that point before bursting.

Compressible soil

Ground that can be squeezed to make room for the expander, such as loose backfill. It keeps displacement close to the pipe and suits bursting.

Connection pit

An excavation at a branch or service connection where the branch is cut off before the pull and remade on the new pipe afterward.

Contingency plan

The contractor's written plan for events such as a stuck head, excessive ground movement, bypass failure or a damaged utility.

Crown

The top inside surface of a pipe. Launch pits are often trimmed so the old pipe's crown is removed back to the spring line.

Curb stop

A shut-off valve on a water service, usually near the property line, used to isolate the service before it is replaced.

Dewatering

Removing groundwater from a pit or around the work with sumps, well points or pumps so the crew can work in dry ground.

Dimension ratio (DR or SDR)

A pipe's outside diameter divided by its minimum wall thickness. Lower numbers mean thicker walls; DR 17 is typical for bursting gravity sewers.

DIPS

Ductile iron pipe size, one of the outside-diameter series for polyethylene pipe in North America, matched to ductile iron fittings.

Ductile iron

A tough iron pipe used for water mains that stretches rather than cracks, so it is replaced by splitting rather than ordinary bursting.

Dynamic head

A bursting head that adds its own force at the pipe, either pneumatic hammer blows or hydraulic expansion, on top of the pull.

Electrofusion

Joining polyethylene with fittings that contain embedded heating wires; an electric current melts the fitting and pipe surfaces together.

Electrofusion saddle

A curved fitting fused onto the outside of a polyethylene main over a cut opening, used to connect a service or lateral.

Encasement

Concrete poured around a pipe, often at an old repair or crossing. It resists bursting and is usually dug out before the pull.

Expander

The widest part of the bursting head. It is sized slightly larger than the new pipe's outside diameter to open room for it.

Facing

Shaving polyethylene pipe ends flat and square in the fusion machine before heating, so the ends meet evenly.

Fusion bead

The double roll of melted polyethylene pushed out inside and outside a butt fusion joint. A uniform bead is a sign of a good joint.

Grade

The slope of a gravity pipe toward its outlet. Bursting generally keeps the old pipe's grade.

Ground heave

Upward movement of the surface caused by soil pushed aside during bursting, most likely over shallow pipe or large upsizes.

Groundwater table

The level below which the ground is saturated. Bursting below it is harder because water flows toward pits and pressures rise around the head.

HDD (horizontal directional drilling)

A steered drilling method that installs pipe along a new underground path. Some systems combine a drill rig with a bursting head.

HDPE

High-density polyethylene, the usual new pipe for bursting because it fuses into a continuous, flexible, slippery string.

Host pipe

The existing pipe that is being burst. It serves only as the guide path for the head.

Hydraulic expansion

A bursting method using a head whose segments are opened and closed hydraulically to push the old pipe apart before advancing.

In-line expansion

Replacing a pipe by bursting with new pipe of the same nominal size; another name for size-for-size bursting.

Invert

The lowest point of a pipe's inside wall, along which the flow travels; slopes and sag depths are measured there.

IPS

Iron pipe size, a common outside-diameter series for polyethylene pipe. A pipe's print line states whether it is IPS or DIPS.

Lateral

The sewer service pipe running from a building to the main. In many cities it is split at the property line between owner and municipality.

Launch pit

The excavation where the head and new pipe enter the host pipe, with a flat section for alignment and a slope sized to the pipe's bend radius.

Lay-down area

The strip of ground behind the launch pit where the new pipe is laid out and fused before the pull. Its length can limit the run.

Locate

Marking the position of buried utilities on the ground before excavation, arranged through a provincial one-call service.

Lubrication

Bentonite or polymer pumped around the new pipe during the pull to cut friction and pulling stress.

Manhole

An access structure on a sewer main. Mains are often burst from manhole to manhole, and worn manholes may be replaced as pits.

MDPE

Medium-density polyethylene, used in some early bursting work and in gas service pipe.

NASSCO classification

A three-level ranking of bursting projects from routine to extremely challenging, based on depth, diameter, upsize, length, trench width and soil.

Offset joint

A joint where one pipe section has shifted relative to the next, leaving a step. It can snag a bursting head.

One-call service

The provincial centre that notifies utility owners to mark their buried lines before digging. In Alberta it is Utility Safety Partners.

Open cut

Replacing a pipe by digging a trench along its whole length. It allows a new grade and route but disturbs the full surface.

Orangeburg

Bituminous fibre pipe made of wood pulp and pitch. It softens and deforms with age and tends to crush rather than crack under a head.

Overcut

The annular gap left between the expanded hole and the new pipe because the expander is larger. It lowers friction but increases displacement.

Oversize

How much larger the expander is than the new pipe, often given as a percentage. The upsizing calculator defaults to 10 percent.

Peak particle velocity

A measure of how fast soil particles vibrate, used in research on how far bursting vibration travels before it becomes harmless.

Pipe bursting

Replacing a buried pipe by breaking it outward with a pulled head while a new pipe is drawn into the same path in one pass.

Pipe reaming

A replacement method using a modified directional drill to grind up a non-metallic pipe and flush it out while pulling in new pipe.

Pipe splitting

Slitting a tough pipe lengthwise with cutter wheels or blades, then spreading it with an expander so a new pipe can follow.

Pneumatic bursting

Bursting with an air-driven hammer inside the head that strikes hundreds of times a minute while a winch keeps tension.

Product pipe

The new pipe installed by bursting, usually fused HDPE.

Pulling unit

The hydraulic puller or winch in the receiving pit that draws the rods or cable, head and new pipe through the run.

Receiving pit

The excavation at the end of the run where the puller sits and the head is recovered and detached from the new pipe.

Relaxation

The recovery of polyethylene after it has been stretched by pulling. Installers let it rest before making final connections.

Repair clamp

A steel or stainless band fitted over a crack in an earlier repair. It resists the head and is usually dug out before bursting.

Rod string

Short steel rods coupled together and threaded through the host pipe to transmit a static pull; removed one by one as the head advances.

Sag

A dip in a gravity pipe below its intended grade, where water and solids collect. See also belly.

Service connection

The joint where a house service meets a main, or a branch meets a lateral. Each one needs an excavation on a bursting job.

Settlement

Sinking of the ground or pipe after work, often over pit backfill or where voids existed around the old pipe.

Size-for-size

Bursting with new pipe of the same nominal size as the old; the lowest-displacement option.

Sliplining

Pushing or pulling a smaller new pipe inside the old one and usually grouting the gap. It reduces the bore; bursting does not.

Sonde

A small transmitter in a camera head or on a cable that lets a locator above ground trace the pipe's route and depth.

Spring line

The horizontal midline of a pipe's cross-section, halfway between crown and invert.

Stall clause

A quote term stating the price and process if the head stops at an unexpected obstruction and an extra pit is needed.

Static bursting

Bursting with pull alone: a solid cone with no moving parts drawn through by a hydraulic rod or cable puller.

Thrust block

A plate or built structure in the receiving pit that spreads the puller's reaction force into the soil.

Transition coupling

A fitting that joins new polyethylene to old pipe of another material, such as cast iron or PVC, at each end of the burst.

Trenchless

Any method of installing or renewing underground pipe without a continuous trench, including bursting, lining and directional drilling.

Upsizing

Installing a larger pipe than the one being burst. One-size and two-size upsizes move to the next or second-next standard size.

Vacuum excavation

Digging with suction and air or water to expose buried utilities safely before and during bursting.

Vitrified clay pipe

Fired clay pipe, often called clay tile, common in mid-century sewers. It is brittle and among the easiest hosts to burst.

Zone of influence

The area around a bursting head where soil moves or vibrates noticeably. It grows with upsizing and denser ground.