The Fit Check scores a line on the factors that make pipe bursting easier or harder: host material, upsizing, depth, ground, nearby utilities, connections and what the camera showed. A total of 0 to 2 reads as a good candidate, 3 to 5 as possible with conditions, and 6 or more as a poor candidate worth comparing with other methods. It is a screening guide, not an engineering assessment.
- Clay, cast iron, unreinforced concrete and Orangeburg start at 0 points; PVC or ABS at 1; ductile iron or steel at 2.
- Rock, cobbles or boulders add the most, 3 points, because the ground cannot compress to make room.
- A sag adds 2 points because bursting generally follows the old line and reproduces it.
- Every result repeats the same prerequisite: a camera run of the whole line, all utilities located and a permit where required.
- The method note suggests split bursting, a splitting head, static or pneumatic, depending on material, upsizing and soil.
Pipe Bursting Fit Check
01 /How do I use the Fit Check?
Choose one option in each of the six drop-downs, tick any camera findings that apply, and read the score, band and reasons. The defaults describe a common starting case: a clay pipe, same size replacement, about 1 to 3 m deep, clay or silt ground, utilities not yet located, no connections along the run and no camera defects ticked. With those defaults the tool scores 2, a good candidate.
- Existing pipe material: vitrified clay, cast iron, unreinforced concrete, Orangeburg (fibre), PVC or ABS, or ductile iron or steel.
- New pipe size: same size, one size up, or two or more sizes up.
- Depth to the pipe: less than about 1 m, about 1 to 3 m, or more than about 3 m.
- Ground: sand or gravel, clay or silt, or rock, cobbles or boulders.
- Other utilities close to the line: none known nearby, not located yet, or within about half a metre.
- Connections along the run: none, one or two, or three or more.
- What the camera showed (tick any): a sag or belly, a collapse or missing section, offset joints, repair clamps or concrete encasement.
If you do not know an answer, pick the less favourable option. The tool is most useful when it tells you what to find out, not when it confirms what you hoped.
02 /How is the Fit Check score calculated?
The score starts from the host material and adds points for each condition that makes bursting harder. There are no negative points: nothing in the tool makes a line easier than its material allows.
| Material | Start | Note the tool shows |
|---|---|---|
| Vitrified clay | 0 | Brittle, bursts cleanly |
| Cast iron | 0 | Brittle; bursts, but heavy walls need a strong pull |
| Concrete (unreinforced) | 0 | Bursts; reinforced concrete is harder |
| Orangeburg (fibre) | 0 | Soft, often crushed rather than burst; camera it first |
| PVC or ABS | 1 | Plastic can stretch instead of fracturing; may need a splitting head |
| Ductile iron or steel | 2 | Does not fracture; needs split bursting with cutter blades |
| Condition | Points | Reason given |
|---|---|---|
| Two or more sizes up | +1 | Displaces much more soil and needs more pulling force |
| Depth under about 1 m | +2 | Shallow lines can heave the surface above the head |
| Depth over about 3 m | +1 | Deep lines need deep, shored pits |
| Clay or silt | +1 | Dense clay resists being pushed aside more than sand or gravel |
| Rock, cobbles or boulders | +3 | Resist displacement and can deflect the head |
| Utilities not located yet | +1 | Every nearby utility must be located before a burst is planned |
| Utilities within about 0.5 m | +2 | May need to be exposed and protected |
| Three or more connections | +1 | Each connection needs its own pit |
| Sag or belly | +2 | Bursting generally follows the old line, so the sag is likely reproduced |
| Collapse or missing section | +2 | Can stop or deflect the head; often needs a pit there |
| Offset joints | +1 | Can snag the head |
| Repair clamps or concrete encasement | +2 | Resist bursting and usually need a pit |
One or two connections and "none known nearby" for utilities add nothing, and neither does a one-size upsize or sand and gravel ground. The bands are 0 to 2 good candidate, 3 to 5 possible with conditions, and 6 or more poor candidate, compare other methods.
03 /How does the tool pick the likely method?
The method note is chosen by a short set of rules, checked in order:
- Ductile iron or steel: split bursting, meaning cutter blades plus an expander.
- PVC or ABS: a splitting head, or confirm the plastic will fracture.
- Two or more sizes up, or clay or silt ground: static bursting is often chosen where control and pulling force matter; pneumatic suits many brittle lines.
- Anything else: static or pneumatic bursting, and the contractor decides.
Because the rules run in that order, a ductile iron line always returns split bursting, even in clay soil with an upsize. The background to each head type is in static vs pneumatic vs split bursting.
04 /What do some worked examples score?
| Line | Points | Score and band | Method note |
|---|---|---|---|
| Defaults: clay, same size, 1 to 3 m, clay soil, utilities not located, no connections, no defects | Clay soil +1, not located +1 | 2, good candidate | Static often chosen; pneumatic suits many brittle lines |
| PVC, same size, 1 to 3 m, sand, none nearby, no connections, offset joints | Start 1, offsets +1 | 2, good candidate | Splitting head, or confirm the plastic fractures |
| Clay, two sizes up, 1 to 3 m, clay soil, none nearby, three connections, sag | +1, +1, +1, +2 | 5, possible with conditions | Static often chosen; pneumatic suits many brittle lines |
| Cast iron, one size up, under 1 m, sand, utility within 0.5 m, two connections, sag | +2, +2, +2 | 6, poor candidate | Static or pneumatic; contractor decides |
| Ductile iron, two sizes up, over 3 m, rock, utility within 0.5 m, three connections, collapse and encasement | Start 2, then +1, +1, +3, +2, +1, +2, +2 | 14, poor candidate | Split bursting |
The fourth example shows how a sound material can still be a poor candidate: a shallow line with a gas service close by and a sag is a bursting problem regardless of how well cast iron breaks.
05 /What should I do with my result?
Every result ends with the same line: before any quote, a camera inspection of the whole run, every utility located, and a permit where your municipality requires one. That is the tool's way of saying the score is only as good as the information behind it.
- Good candidate (0 to 2): get a camera survey if you have not, and ask bursting installers to price it. Read what the survey should include.
- Possible with conditions (3 to 5): each reason listed is a condition to resolve, such as a sag to dig, a utility to expose or a clamp to remove. Ask installers how they would handle each one.
- Poor candidate (6 or more): compare with lining and open cut; see bursting vs lining and bursting vs open cut. Bursting may still work for part of the line.
To see how much ground the head will push aside for your sizes, use the Upsizing & Displacement Calculator. Clearances are explained in risks and problems. When you are ready, send your camera report and result.
FAQQuestions people ask
Why does a sag count so heavily in the Fit Check?
Because bursting generally follows the old pipe. A belly in the host is likely to end up in the new pipe unless it is dug and re-bedded first.
Why does clay soil add a point but sand does not?
Dense clay resists being pushed aside more than sand or gravel, so bursting needs more force and can move the ground further.
Can a poor Fit Check score still be burst?
Sometimes, with changes: digging the sag, exposing the utility, removing the clamp or bursting only part of the run. The score shows what has to be solved.
Does the Fit Check work for water lines?
It was written for sewer laterals but the factors apply broadly. Water services are usually ductile metal, which starts at 2 points and returns split bursting.
What if I am unsure what my host pipe is made of?
Choose the least favourable likely option, then book a camera inspection. The camera answers material, depth, defects and connections at once.
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