Sewer Inspection Standards

Why coding standards matter more than cameras

Two crawlers with different cameras can still produce comparable results if their operators code what they see in the same way. Coding systems give every defect, from cracks and deformation to roots, deposits and infiltration, a defined code with standard details for position and extent. That lets an asset owner compare surveys done years apart by different contractors, rank pipes for repair and feed condition data into planning software. Without a shared system, a survey depends on each reviewer's own words and is hard to analyse at scale. Before choosing equipment such as the Envirosight ROVVER X or RedZone Solo, settle which coding standard your client requires and check that the reporting software supports it.

EN 13508-2 across Europe

In Europe the reference is EN 13508-2, published in the UK as BS EN 13508-2:2003+A1:2011, Investigation and assessment of drain and sewer systems outside buildings: visual inspection coding system. BSI describes its scope as gravity drain and sewer systems from the point where wastewater leaves a building or roof drainage system, or enters a road gully, to the point where it is discharged into a treatment works or receiving water. It specifies a coding system for recording the visual information from an inspection objectively. National bodies may add their own manuals and grading rules on top of that coding system, so ask your client which national version and grading method apply before the first survey.

PACP grades defects from 1 to 5

For North American work, the system to know is NASSCO's Pipeline Assessment Certification Program, known as PACP. A NASSCO article by certified trainer Tanya Stephens explains that each defect is graded from 1 to 5, with higher numbers more severe, and that structural and operation and maintenance defects are graded separately so they reach the right team. PACP summarises a pipe through Quick Ratings, a four-character code showing the worst conditions, and a Pipe Rating Index giving the average severity. The NASSCO article warns that averages can mislead, since six grade 1 defects can hide six grade 5 defects in the same section, so prioritise from the worst defects as well as the averages.

Set up surveys that compare over time

Comparable data starts before the crawler goes in. Agree the coding standard, its version and the grading method, along with the convention for naming each pipe length between access points, and write them into the survey specification. Require trained or certified coders, and spot-check a sample of their coding against the footage. Record the direction of survey, the start and finish points, any abandoned lengths with reasons and conditions such as flow depth, since water in the pipe can hide defects along the invert. When you compare robots such as the Sewer Robotics LISY or SuperDroid Pipe Robot, ask whether their software exports coded data in the format your asset system reads, not only video.

Sources and further reading

• BS EN 13508-2:2003+A1:2011 Investigation and assessment of drain and sewer systems outside buildings: visual inspection coding system — BSI (British Standards Institution).
  The European coding system for recording what sewer and drain inspections show, as published in the UK.
• PACP Condition Grading System — NASSCO.
  NASSCO trainer's explanation of PACP defect grades, structural and O&M scores, Quick Ratings and averaging pitfalls.

Common questions

How long does a sewer CCTV survey take?

It depends on pipe length and diameter, access, cleaning needs and flow. Ask contractors to quote the length they expect to survey per shift in your conditions, and allow separate time for coding and quality checks after the fieldwork before reports are due.

Do I need certification to code sewer inspection footage?

For PACP work, clients often require coders certified through NASSCO training, and European clients may ask for training in the national manual that applies EN 13508-2. Check the survey specification first, because uncertified coding can be rejected and the survey repeated at your cost.