CCTV survey report explained (defect codes and gradings)
WRc defect codes, severity grades and what 'CR Grade 3' actually means — translated into plain English.
If you've just received a CCTV drain survey report and the codes look like Greek, this guide translates the most common ones.
How reports are structured
Every report follows the WRc Manual of Sewer Condition Classification (MSCC) — the UK industry standard since the 1980s. Reports list each defect with:
- A code (what type of defect)
- A severity grade (1 = trivial, 5 = critical)
- A chainage (how far along the pipe)
- A clock position (where on the pipe wall, like a clock face)
The most common codes
| Code | Meaning | Plain English |
|---|---|---|
| CR | Crack | A line break in the pipe wall |
| F | Fracture | A complete break, possibly with displaced pieces |
| DEF | Deformation | The pipe is misshapen (often plastic under load) |
| D | Deposits | Build-up of debris (further coded as DES = settled, DEF = attached fat/grease, DER = roots) |
| RI | Root intrusion | Roots growing into the pipe |
| JDL/JDM/JDS | Joint Displaced (Large/Medium/Small) | The pipe has moved at a joint |
| OB | Obstruction | Something solid in the pipe |
| CN | Connection | Where another pipe joins |
| WL | Water level | How much standing water (problem if persistent) |
Severity grades — what action is needed
- Grade 1: Minor, no immediate action. Note for monitoring.
- Grade 2: Minor defect, repair if convenient.
- Grade 3: Significant — repair recommended within 12 months.
- Grade 4: Serious — repair recommended within 3 months.
- Grade 5: Critical — immediate repair. Risk of failure or collapse.
A worked example
'CR Grade 3 at 4.2m, 12 o'clock'
Means: a crack in the pipe wall, severity 3 (significant), 4.2 metres along the run, on the top of the pipe (12 o'clock as you look in the direction of flow). Likely repair recommendation: patch lining at that location.
What to ask
If any defect in your report is Grade 3 or higher, ask the surveyor for a written repair quote with options. A good report doesn't just tell you what's wrong — it tells you what your choices are and what they cost.