A CCTV drain inspection report that says “root intrusion, moderate” tells you something is in your pipe, but not much about what to actually do next. Root intrusion severity grading turns a vague finding into an actionable one, translating what the camera sees into a scale that indicates how urgently a repair is needed and which repair option is realistic. This guide covers how those grades are assigned, what they mean for pipe condition, and how to read them alongside the rest of your report.
Quick answer (BLUF)
Root intrusion severity is typically expressed as a bore occlusion percentage (how much of the pipe’s internal diameter the roots occupy) mapped onto a simple grading scale, minor, moderate, severe, or a numbered condition grade from 1 to 5. Minor intrusion (a few thread roots, under roughly 15% occlusion) is often monitored rather than repaired immediately. Moderate intrusion (15-40% occlusion) is where most contractors recommend scheduling relining before it becomes an emergency. Severe intrusion (40%+ occlusion, or a root mass causing active blockages) generally needs prompt attention. The percentage matters more than the label, always ask for the number behind the word.
Why root intrusion gets its own severity scale
Root infiltration is the single most common structural defect found in Central Coast CCTV inspections, and it behaves differently from other defects a camera picks up. A crack or an offset joint is a fixed, static condition, it’s exactly as bad on the day it’s found as it will be next month, barring further ground movement. Root intrusion is not static. Roots that have found an entry point keep growing, and the same joint that shows a handful of fine root threads today can be substantially more occluded within twelve months, particularly through spring and summer growth periods. A severity grade is really a snapshot of a moving target, which is why the grading system needs to communicate not just how bad things are now, but how urgently that trajectory needs to be interrupted.
How bore occlusion percentage is assessed
The camera operator estimates what proportion of the pipe’s internal cross-section is occupied by root mass at the point of entry, expressed as a percentage of the bore. This is a visual assessment made against the known internal diameter of the pipe, and it’s usually recorded at the single worst point along an affected joint or crack, since root density is rarely uniform across an entry point.
This percentage feeds directly into severity labelling:
Minor (roughly under 15% occlusion). A small number of fine, thread-like roots entering at one joint or crack. Flow is essentially unaffected. This is the finding on a lot of ageing terracotta pipe that hasn’t caused a blockage yet and may not for some time.
Moderate (roughly 15-40% occlusion). A denser root mass, sometimes described as looking like a fine root ball or mat, that’s starting to reduce effective flow capacity and will catch debris such as wet wipes, sanitary products or grease that would otherwise pass through. This is the range where the pattern of intermittent slow drainage typically begins.
Severe (roughly 40%+ occlusion). A substantial root mass filling much of the visible bore, frequently already associated with a recent or current blockage. At this level, roots have usually been established at the entry point for an extended period, and the joint or crack itself has likely widened further as root growth physically forces the gap open.
Condition grade numbers and how they map to root intrusion
Many contractors, ours included, also report using a simple 1-5 condition grade that folds root intrusion severity together with the structural defect it’s entering through, since the two are related but not identical questions.
| Grade | General meaning | Typical root intrusion correlation |
|---|---|---|
| Grade 1 | No defects found | No root intrusion present |
| Grade 2 | Minor defects, monitor | Minor root intrusion at an otherwise sound joint |
| Grade 3 | Moderate defects, maintenance recommended | Moderate root intrusion, joint or crack visibly open |
| Grade 4 | Significant defects, repair required | Severe root intrusion or moderate intrusion at multiple points along the run |
| Grade 5 | Critical defects, immediate action required | Severe root intrusion actively restricting flow, often with a recent blockage history |
A Grade 3 or 4 rating isn’t only about the root mass itself, it also reflects the underlying joint or crack that let the roots in, since that entry point is what a repair actually needs to address. Two pipes with an identical root mass can receive different grades if one has a single small joint gap and the other has a wider, more structurally compromised opening behind the roots.
WSAA defect codes for root intrusion
Reports from technically rigorous operators may reference the Water Services Association of Australia’s standardised coding system alongside the descriptive grade. The most common code for this defect is RFI (root infiltration), sometimes further qualified as RFB (root ball, a substantial rounded mass) or RFT (root tap, a single dominant intrusion point). These codes give a consistent, contractor-independent description of what was found, useful if you’re comparing reports from different providers or getting a second opinion. See our CCTV drain inspection report explained guide for how these codes fit into a written report.
What severity actually changes about the recommendation
The practical value of a severity grade is what it tells you about timing and repair scope, not just the finding itself.
Minor intrusion at a single joint is frequently a “monitor and re-inspect in 12 months” recommendation, particularly if the pipe is otherwise sound and there’s no blockage history. Relining a pipe for a few thread roots at one joint isn’t usually cost-effective when the rest of the run shows no issues.
Moderate intrusion, especially if found at more than one point along the run, is generally where a relining recommendation starts to make clear sense. Left alone, moderate intrusion reliably progresses to severe within a year or two on the Central Coast’s typical growing conditions, and addressing it on your own schedule, rather than the pipe’s, avoids the cost and disruption of an emergency callout.
Severe intrusion usually means the pipe needs attention promptly, sometimes the same visit if a blockage brought you to a CCTV inspection in the first place. A full-length reline is more often the right scope than a single point repair, since severe intrusion at one location frequently correlates with earlier-stage intrusion elsewhere in the same run.
Location and position also affect the picture
Severity percentage isn’t the only variable that matters. A root mass at the invert (the bottom of the pipe, roughly the 6 o’clock position) sits directly in the path of solids and debris, and tends to cause blockages at a lower occlusion percentage than an equivalent mass higher up the pipe wall, which flow can move around more easily. Two findings with the same bore percentage can carry different practical urgency depending on exactly where the roots are sitting, which is why a good report records clock position alongside the severity grade rather than relying on the percentage alone.
Frequently asked questions
My report says “moderate” root intrusion but doesn’t give a percentage, should I ask for one? Yes. The descriptive label alone (minor, moderate, severe) is a reasonable shorthand, but the underlying bore percentage gives you and any second contractor a much more precise, comparable basis for a decision, particularly if you want a second opinion or are comparing quotes from different providers.
Does minor root intrusion always progress to moderate and then severe? Not on a fixed timeline, but the general direction is almost always toward worse rather than better, since roots that have found a moisture source don’t retreat on their own. How quickly it progresses depends on the tree species nearby, the size and orientation of the joint gap, and seasonal growing conditions. This is exactly why a “monitor” recommendation still comes with a re-inspection interval rather than being a one-time dismissal.
If two joints show root intrusion at similar severity, does that mean the whole pipe needs relining rather than a point repair? Often, yes. Root intrusion at multiple separate points along a run is a reasonable indicator that the pipe material and jointing method throughout that run is reaching the end of its serviceable life, not just that two specific joints happened to fail. A full-length reline addresses the whole run in one job rather than treating each point in isolation as new defects continue to emerge.
Can root intrusion severity be graded from a video alone, or does it need a live inspection? Footage alone is generally sufficient for an experienced operator to assign an accurate severity grade, since the percentage assessment and clock position are both visual judgements made from what the camera records. A live inspection lets the operator direct extra attention to a borderline finding in real time, but it isn’t strictly necessary for grading footage after the fact.
Is severe root intrusion always a sign the pipe itself needs replacing rather than relining? No. Relining addresses the root intrusion and the joint or crack it entered through regardless of severity, provided the pipe bore is still intact enough for a liner to pass through. Replacement becomes the fallback only where the pipe has also physically collapsed or displaced badly enough to block the liner’s path, which is a separate finding from root intrusion severity itself.
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