From the magazine


Can you give a general overview of Unitywater’s pipe assets and how often Unitywater conducts CCTV inspections of these assets?

Unitywater has 5,449 km of sewerage infrastructure, with pipes ranging in diameter from 150-2,400 mm.

More than half of these assets, about 56 per cent, are unplasticised polyvinyl chloride (uPVC). Of the remainder, 15 per cent are asbestos cement, 22 per cent are vitrified clay and 7 per cent are made from other materials.

Unitywater’s approach is to inspect large-diameter mains (of greater than 375 mm) on a ten-year cycle program. Unitywater has 220 km of these pipes and the inspection program covers 22 km per year.

For the smaller sewerage pipes of diameters ranging from 150-375 mm, these are scheduled for inspection over a 25-year period at a rate of about 120 km per year.

What sort of CCTV technology is preferred?

Unitywater crews use pan-and-tilt cameras mounted on tractors to conduct in-house surveys and request the same from contractors.

Does Unitywater have an in-house CCTV team or does it tender the task out to preferred contractors?

Unitywater operates two camera teams equipped to survey 150-375 mm diameter sewers. Contractors are used for diameter sizes of 375 mm and above, but can also be utilised to inspect smaller sewer pipes when required.

What are some of the most common forms of wear and tear found using CCTV?

Common issues identified are tree root intrusion, pipe cracking and service pipe defects.

Structural defects commonly range from longitudinal or circumference cracks and debris build-up, through to rubber ring deterioration that causes pipes to drop at joints.

Unitywater follows the Water Services Association of Australia guideline for CCTV to identify, classify and grade each defect type.

What happens once a fault has been spotted? What is the most common repair process?

Unitywater follows an internal governance process to ensure investment is both prudent and efficient.

When faults are identified, they are assessed for potential or actual customer impact, solution/restoration cost and then prioritised in the capital program.

Monitoring is maintained until restoration is completed.

Some common repair practices are replacement and lining together with root cutting.

In your view, are there any limitations on the current technology and how would you like to see it develop in the future?

Combining the inspection with the repair process would save time and cost associated with return visits.

This would improve the customer experience and could help focus on ways to repair uPVC and PE pipes, especially as this material type will increasingly dominate asset classes.

Additionally, improvements in the communication technologies would allow direct connection to geospatial information systems – in effect giving a “÷Street View’ for sewers.

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