Most bursting pulls in high-density polyethylene (HDPE) because it can be heat-fused into one continuous, jointless string, bends gently into the launch pit and slides through broken pipe without snagging. Wall thickness is set by the dimension ratio; DR 17 is the usual gravity-sewer choice. The pipe stretches slightly on the pull, so it is left to recover before the final connections are made.
- Fused HDPE arrives at the far pit as one pipe with no gasketed joints along the burst length.
- Dimension ratio is outside diameter divided by wall thickness: a lower DR means a thicker wall, a stiffer pipe and a higher pull rating.
- Butt fusion heats and presses square-cut pipe ends together; done to procedure, the joint is as strong as the pipe.
- HDPE stretches under pulling load and shrinks and grows with temperature, so installers let it rest before tying in.
- Industry lifespan figures for PE pipe are estimates that assume correct design and installation, not a warranty.
01 /Why is HDPE the default pipe for bursting?
HDPE suits bursting because of three properties the PPI Handbook of Polyethylene Pipe calls continuity, flexibility and versatility. Continuity comes from butt fusing long lengths into a single string in the field, so there are no joints to catch on fragments during the pull. Flexibility lets the string curve down into the launch pit at an angle instead of needing a pit as long as the pipe. Versatility means the same material family is used for sewer, water and gas.
Its surface also helps. Polyethylene is slippery against soil and broken pipe, which keeps pulling forces down, and its interior is smoother than clay or concrete, which improves flow. The PPI handbook uses a Manning roughness of about 0.009 for PE against roughly 0.012 to 0.015 for clay and concrete.
Other pipe can be installed by bursting. The handbook notes that ductile iron, clay and concrete pipes can be jacked in behind a static head in short segments with joints designed for the purpose. On residential work those are rare; fused HDPE is what you will almost always be quoted.
02 /What do DR and SDR mean on a bursting quote?
DR, or SDR for standard dimension ratio, is the outside diameter divided by the minimum wall thickness. HDPE is made to a fixed outside diameter, so a lower ratio means a thicker wall and a smaller bore. For example, a pipe with a 168 mm outside diameter at DR 17 has a wall of roughly 10 mm; at DR 11 the wall is roughly 15 mm.
| DR | Wall | Where the handbook places it |
|---|---|---|
| DR 21 | Thinnest listed | Short runs where high pulling forces are not expected; thin walls tend to stretch more |
| DR 19 | Thin | Shorter, smaller-diameter gravity applications |
| DR 17 | Medium | Typical for bursting gravity sewers, and pressure pipe with design pressure under about 100 psi |
| DR 11 | Thick | Pressure pipe where about 150 psi is required |
A quote that says only "HDPE" is incomplete. It should state the nominal size, the outside diameter series, the DR and whether the pipe is rated for sewer, pressure or potable use. North American HDPE comes in iron pipe size (IPS) and ductile iron pipe size (DIPS) outside diameters, so two "6-inch" pipes can differ in actual size; the print line on the pipe states which it is.
03 /How is a butt fusion joint made?
Butt fusion joins two pipe ends by melting them and pressing them together. The PPI handbook lists six steps: secure the pipe in the machine's clamps, face the ends square, align them, melt the ends against a heater plate, join them with the correct fusion force, and hold under pressure until the joint cools. When fused to the pipe maker's procedure, the handbook says the joint becomes as strong as the pipe in both tension and pressure.
- Clean and clamp
Both pipe ends are wiped clean and locked into a fusion machine that holds them on a common centreline.
- Face
A rotating facer shaves the ends until they are flat, parallel and square; shavings should come off in continuous ribbons from both pipes.
- Align
The ends are brought together to check that the outside walls line up with no visible step.
- Heat
A temperature-controlled heater plate is inserted and the ends are pressed lightly against it until a melt bead forms around each.
- Join
The plate is removed quickly and the ends are pushed together at the specified pressure, rolling the melt into a double bead.
- Cool
The joint is held under pressure for the specified cooling time before the machine is opened and the pipe is moved.
The handbook points to the PPI's generic butt fusion procedure (technical report TR-33) and ASTM F2620 as the references most pipe makers align with. Ask who will fuse your pipe, whether they are trained on the procedure used, and whether the machine records heating and cooling times. On larger projects a data logger printout for each joint is common.
04 /Why does the pipe need to rest before it is connected?
Polyethylene stretches under load and changes length with temperature, and both effects matter at the pits. The EPA fact sheet lists as a disadvantage that the replacement pipe can stretch as it is pulled and retract afterward, leaving gaps at the manhole or connection where it was inserted.
- Stretch. The PPI handbook suggests that when pipe has been pulled to a significant share of its allowable tensile load, it may be prudent to let it rest before connecting it to fittings, manholes and laterals, so it can rebound.
- Temperature. The same handbook gives PE's length change as about one inch per 100 feet for every 10 °F change. In very hot or cold weather, when the pipe on the surface is far from ground temperature, it recommends a 12 to 24 hour rest before tie-ins.
- Safe pull. The handbook tabulates safe pulling stress by resin and load duration, and notes that below 3 percent strain the pipe essentially recovers completely after pullback.
On a small residential lateral pulled a short distance on a mild day, the rest may be short. On a long pull in January, it matters more. Either way, ask the installer what their procedure is and how the end connections allow for movement.
05 /How tight can HDPE bend, and how do you protect it on site?
The PPI handbook says PE pipe can be cold bent to a radius of roughly 25 to 30 times its outside diameter depending on DR. For a 168 mm pipe that is about 4.2 to 5.0 m, which is why the launch pit needs a sloped entry and why the fused string does not have to be laid out in line with the old pipe.
| Issue | What good practice looks like |
|---|---|
| Dragging over pavement | Pipe sits on rollers or offcuts rather than grinding along concrete |
| Kinking at the pit | Entry slope long enough for the bend radius; no forcing with the excavator bucket |
| Scratches and gouges | Head end inspected when it reaches the receiving pit; the handbook rejects defects deeper than 10 percent of the wall |
| Contamination | Ends of water pipe capped during layout and pull |
| Cold weather | Fusion sheltered from wind; pipe rested before tie-in |
Fragments of clay, cast iron and concrete generally do not cut PE. The handbook cites research in which grooves from bursting brittle pipe were very shallow and narrow, with the exception of splitting ductile iron, where it suggests limiting the upsize or using pipe with a harder outer layer.
06 /How long does HDPE last after a burst?
Nobody can give you a verified lifespan for your particular line. The PPI handbook states the PE pipe industry's own estimate of a service life of 50 to 100 years, conservatively, provided the system is properly designed, installed and operated. That is an industry estimate, not a warranty, and it assumes good fusion, correct DR, proper bedding at the pits and sound connections.
In practice, the weak points of a burst line are rarely the polyethylene itself. They are the transition couplings to old pipe at each end, the service reconnections, and any sag the burst inherited. Check what an installer's warranty covers in the contractor survey guide, and read about grade in sags and grade. For costs, see pipe bursting cost.
FAQQuestions people ask
What does DR 17 mean on HDPE sewer pipe?
The outside diameter is 17 times the minimum wall thickness. The PPI handbook calls DR 17 the typical choice for bursting gravity sewers.
Is fused HDPE really jointless?
Along the fused string, yes: the fusion joints become part of the pipe. The only mechanical joints are the transitions at each end and the service connections.
Why is my new sewer pipe black?
Most HDPE pipe is black because carbon black is added to protect it from sunlight during storage and installation. Some pipe has a coloured stripe or inner layer.
Can HDPE be connected to my old cast iron or PVC?
Yes, with transition couplings or fittings designed for the two materials. The PPI handbook notes PE joins other materials through compression fittings, flanges or qualified transition fittings.
How long should HDPE rest after a pull?
It depends on pull load and temperature. The PPI handbook suggests 12 to 24 hours before tie-ins in extreme heat or cold, and resting when the pipe was pulled hard.
Does cold weather affect HDPE fusion?
Cold and wind cool the heater plate and pipe ends, so fusion is sheltered and done to the maker's cold-weather procedure. Ask how the crew handles it in winter.
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