bom national report image

BOM National Performance Report 2020-21: A wastewater snapshot

BOM National Performance Report 2020-21:

A wastewater snapshot

Each year the Australian Bureau of Meteorology releases the National Performance Report for urban water utilities, the 2020-21 report is available for public download here:

This annual report aims to provide benchmarking of pricing and service quality for urban water utilities. The report is helpful for utilities to monitor annual trends within their own organisations, as well as look at whether their key metrics sit within the typical range in a broader national context. Utilities are grouped within four size categories (small, medium, large, major). This reflects that revenue base and population density can be a factor in both the cost required to provide water and sewer to customers as well as the level of service that is appropriate or sustainable.

Running to 128 pages, this is a comprehensive report that lists metrics across 166 categories from 86 utilities.  Dependent on your area of expertise or interest, there is interesting information for everyone.

Figure 1 – Australian utilities that submitted data for the 2020-21 report.

This article summary focuses on some of the key metrics that relate to gravity sewer mains and wastewater expenditure.

Sewer Main Breaks and Chokes

To enable comparative analysis, many of the metrics are reported as ‘per 100km of asset’, this is the case for ‘sewer mains breaks and chokes’.1 This last year has seen improvements for many locations with 57% of utilities reporting a decrease in breaks and chokes compared to the previous reporting year with Clarence Valley Council, Gippsland Water, and Gladstone Regional Council all seeing reductions of > 75%.

Utilities reporting the lowest instance of breaks and chokes in each utility group size is listed in the table below.

Table 1: Number of sewer mains breaks and chokes per 100 km (Indicator A14)

Utility GroupUtilityValue
Small (10,000 – 20,000 properties)Water Corporation – Geraldton (WA)3.4
Medium (20,000 – 50,000 properties)Tweed Shire Council (NSW)1
Large (50,000 – 100,000 properties)Gippsland Water (VIC)1.5
Major (100,000+ properties)City of Gold Coast (QLD)3.8

Major utilities saw the largest improvement for this metric. However, reductions were not the norm for small-sized utilities with the median increasing from 13.7/year to 15.6/year, and the average increasing from 25.3/year to 35.5/year.

Capital Expenditure per Property (Wastewater)

The report notes that the national median per property capital expenditure on wastewater services decreased by 11% from 2019-20 to 2020-21.

Utilities reporting the lowest wastewater expenditure per property in each utility group size is listed in the table below.

Table 2: Capital expenditure per property – wastewater (Indicator F29)

Utility GroupUtilityValue
Small (10,000 – 20,000 properties)Gympie Regional Council (QLD)$88.90
Medium (20,000 – 50,000 properties)Dubbo Regional Council (NSW)$3.65
Large (50,000 – 100,000 properties)Power and Water Corporation – Darwin (NT)$146.72
Major (100,000+ properties)City West Water Corporation (VIC)$143.57

Looking more closely at the data split by utility size, the average annual capital expenditure on wastewater is surprisingly similar across all utility sizes; in the region of $275 to $300 per property. The reported figures over the last decade do indicate that small and medium sized utilities may be investing less, on average, on wastewater infrastructure.

While there may be a variety of reasons for this, it will be of some concern if a trend of reduced investment is reflected in a similar reduction in wastewater service level KPIs (including sewer main breaks and chokes).

Figure 2 – Capital Wastewater Expenditure per Property

Despite the significant reported drop in per property wastewater expenditure over the last year (11%); the overall reported capital expenditure on wastewater has remained reasonably stable since 2017 at around $2.7 billion dollars per year – with a drop of 2.9% from 2019-20 to 2020-21 based on reported figures.

Figure 3 – Capital Wastewater Expenditure

Wastewater Operating Cost per Property

The report saw 66 of 86 utilities submit data on operating cost per property to supply wastewater services. The following utilities in each category reported operating their networks at the lowest cost:

Table 3: Wastewater operating cost per property (Indicator F14)

Utility GroupUtilityValue
Small (10,000 – 20,000 properties)City of Kalgoorlie-Boulder (NT)$168.96
Medium (20,000 – 50,000 properties)Rockhampton Regional Council (QLD)$294.59
Large (50,000 – 100,000 properties)Toowoomba Regional Council (QLD)$243.35
Major (100,000+ properties)South Australian Water Corporation (SA)$231.92

Residential Wastewater Bill

The cost to provide services is impacted by a wide range of factors, including but not limited to: age of assets, condition of assets, density of population, climate and topography. The table below lists the lowest residential wastewater bill in each category for the 20/21 period.

Table 4: Typical residential wastewater bill (Indicator P14)

Utility GroupUtilityValue
Small (10,000 – 20,000 properties)Armidale Regional Council (NSW)$465
Medium (20,000 – 50,000 properties)Lower Murray Water (VIC)$491.84
Large (50,000 – 100,000 properties)North East Region Water Corporation (VIC)$239.16
Major (100,000+ properties)City West Water Corporation (VIC)$347.92

The report indicates 57% of utilities had a reduction in the typical residential wastewater bill with Central Coast Council seeing the largest change (-24%). However nationally, the overall trend was only marginal (<1% decrease).

1 Wastewater mains breaks and chokes is intended to include:

  • Gravity sewer mains
  • Rising (pumped) mains
  • Low pressure mains
  • Vacuum system mains

It excludes:

  • Property connections
  • Treated effluent mains
  • Recycled water mains

It can be questioned whether failures on pumped rising mains and chokes within gravity sewer networks should fall under the same metric. While these asset types are intrinsically connected to form the majority of a sewer network, they operate under very different conditions and the mode and cause of failure are often quite distinct.

The information and data for this snapshot is sourced from Part A and Part B of the National performance report 2020–21: urban water utilities. It has been used under the Creative Commons Attribution 3.0 Australian License.

Found the article interesting? Check out our case studies here VAPAR case studies.

Heavy rain in a city

What are combined sewer overflows?

What are combined sewer overflows?

Image showing heavy rain on a city street

Early underground pipe systems, such as those in the United Kingdom, were built before separation of wastewater and rainwater pipes were common practice. These types of systems are called combined sewer systems.

A combined sewer overflow (CSO) event is the term used to describe when the capacity of the pipe to carry wastewater and rainwater at the same time is too much for the system to deal with, and the system overflows.

The consequence of CSO events can have a very serious impact on the environment and public health. For this reason, most water utilities have a regulator that monitors the performance of the water utilities to ensure pipe networks operate in a safe way. In the United Kingdom, this performance is monitored by the Environment Agency and regulated by OFWAT, who have recently started to undertake further investigations on the release of unpermitted sewage discharges into rivers and watercourses by some UK water companies. In Australia and the USA, the regional Environmental Protection Agency (EPA) organisations regulate and fine water authorities that are not operating in accordance with certain agreed criteria.

What causes a combined sewer overflow?

A combined sewer overflow (CSO) will most likely happen when both the wastewater and surface water experiences high flow at the same time. For example, when there is a lot of rainfall, and a lot of people at home flushing toilets, showering and cooking, placing greater demand on the sewer pipe network.

Picture showing difference in combined sewer overflow over dry and wet weather conditions
*POTW is a publicly owned treatment works
Source: U.S. Environmental Protection Agency, Washington, D.C. “Report to Congress: Impacts and Control of CSOs and SSOs.” Document No. EPA 833-R-04-001

There are lots of factors that can increase the likelihood and occurrence of a Combined Sewer Overflow, such as rainfall, population growth, and pipe condition. With increasing areas of land being paved, an increasingly urban population that each uses ~150L per person per day, and increased intensity of rainfall as the climate changes, the pipe networks built during the 19th century are unable to adapt.

What is the water industry doing about Combined Sewer Overflow?

Most combined sewer systems will be designed to overflow at a specific point in the network that will minimise damage and risk to the public and the environment. Because an overflow would usually occur when there is a high rainfall event, rainwater would dilute the raw sewerage, minimising (but not eliminating) the impact of the overflow. If the system was built without a designed overflow point, then whenever there are high flow events, sewerage may backflow to the nearest exit point, which may be directly into some unfortunate persons’ property.

To tackle this problem, some water utilities have been installing monitoring devices at commonly overflowing points in their pipe network. These devices send a signal to the water companies to let them know if the level of sewage in the pipe/structure is rising more than usual. If the level of sewerage reaches a certain value, an early warning alert is sent to the water company to let them know that an overflow may be imminent so that they can take action if required.

How can spills from combined sewer overflows be prevented?

Adding storage capacity to the network

In addition to some of the initiatives being undertaken by water companies described above, prevention of these types of overflows could also come adding storage capacity to the network. By increasing the capacity of the network to not only convey, but store (for a short period of time), it is possible to reduce the incidence of sewer overflows. This can come in the form of storage/detention tanks for both sewage and surface water.

Increase the treatment capacity of the network

Another option is to increase the treatment capacity of the network so that the sewage can be turned into good quality water faster, leaving more capacity in the network to convey sewage during times of high flow. A key element to the efficacy of treatment in the network to reduce CSO’s is to also make sure the upstream and downstream network from the overflow structure are in optimum condition. If these pipes fail or get blocked, then treatment capacity is greatly reduced.

A great example of increasing the storage and treatment capacity of a combined sewer network to prevent CSOs is the Thames Tideway tunnel. Reconnecting London with the River Thames. This project both increases the storage capacity of the network, and increasing the treatment capacity of the network by routing sewage to an upgraded treatment plant.

Separating the sewer and surface water pipe network

This is an option, though depending on the level of existing infrastructure development not always a practical one. For newer developments, this is a great option to increase the conveyance capacity of a network to a downstream treatment source. A key challenge with separated systems is that regular monitoring of any new building developments is needed to reduce/eliminate illegal surface water connections into the sewer network. These illegal connections are either done mistakenly or deliberately, brought about when a surface water pipe is not available.

About the Author Amanda Siqueria

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Road collapsed due to sewer failure

Things you need to know about sewer network maintenance

Things you need to know about sewer network maintenance

Are you having trouble getting approval for a routine inspection program for your sewer network? Here is some information to bolster your business case.

The Challenge

Councils and utilities are rarely in a position to inspect 100% of their sewer or stormwater networks. This means that careful selection is required when planning which pipes, manholes, and pits to inspect. This should involve risk-based decisions that often include a focus on high consequence of failure locations. However, risk is a combination of both consequence and likelihood of failure. For sewer networks, there is often a significantly increased likelihood of failure immediately downstream of sewer rising mains (pumped mains) due to sulphuric acid generation

What causes hydrogen sulphide corrosion in sewers?

Sulphate in sewage is converted to hydrogen sulphide (H2S) by bacteria present in the sediment/biofilm layer. The H2S can move from the liquid to gas phase which is often the cause of customer odour complaints. Sulphur oxidising bacteria (SOB) above the water level convert this gas to sulphuric acid which can be highly corrosive to the surface of concrete manholes and pipes.

Why are inspections necessary?

The cost and the associated impact of a partial or full failure of these assets can be significant. Understanding where these issues are likely to occur, the current condition of these assets, and the rate of condition change over time allows better management of risk and can save large reactive repair expenses.

What can I do about managing these assets?

Periodic inspection of the first few manholes downstream of rising main outlets and the receiving gravity pipework (especially if concrete/asbestos cement) is a prudent investment and recommended as a subset of your broader condition inspection programming. The image above is an example of proactive rehabilitation of two manholes just downstream of a rising main. This planned work is a fraction of the cost of dealing with a reactive repair after failure.

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AI in Sewer

AI in Sewers

AI in Sewers

The importance of the pipe network beneath out feet

Our cities and suburbs are supported by a vast underground network of water, wastewater and storm water infrastructure. This network of gravity pipes, pumps and filtration systems play a very important role in the quality of our life, eliminating disease, safeguarding the environment, and protecting communities.

However, parts of this aging infrastructure are nearing the end of its useful life and now (more than ever) requires closer attention. Without attention, this situation is not sustainable.

Most of our water and wastewater infrastructure were installed during the 19th century and municipalities are facing the challenge of broad-scale infrastructure replacements or repairs costing hundreds of millions of dollars.

Adding to all this is the changing climate factor, meaning systems that were designed 30 or so years ago may not be sufficient to support everchanging environment around it.

To extend the life of infrastructure, reliance on smart city technology capabilities is critical. By creating visibility into buried assets to understand the conditions of underground infrastructure, utilities can compare current performance with expectations, and predict when and where problems may arise. This also leads the way to prioritisation of maintenance work, decreasing downtime of the assets, resulting in reduced interruptions.

Today’s technology

With sensors and actuators becoming more cost effective, an array of technologies is becoming available for the pipe industry. For pressure pipes or pipes transporting materials under high pressure, static sensors are being used to help monitor the health of the asset. In sewer and stormwater applications, inspection by video still is widely adopted with assessment being carried out visually by an expert.

With operational technology (OT) and information technology (IT) coming together, data that were once only available in isolated networks is now available via the world wide web. What this means is CCTV operators are no longer needing to download inspection videos to a hard-drive in order to assess the condition of the pipe in the office, instead they can upload the video file over the cloud.

AI at your service

With more data being available and accessible, a path has been paved for advanced technology such as artificial intelligence or AI. These smart algorithms feed on data, in-fact, the more data that is available, the quicker and more accurate an AI system can become.

Like other technologies, AI is tool to better understand a problem so to make data driven decisions. One of the areas where AI is helping the pipe industry is in the field of video processing. The traditional means of CCTV condition assessment presents several challenges including time taken to review the videos and identify defects, the operator subjectivity and field conditions making visual inspections difficult.

The AI models are pre-trained to detect certain anomalies, in this case pipe features and defects. The inspection video is then ingested and inferenced against the trained model. The result is the identification of the type and importance of anomalies.


Integrating the above-mentioned technologies, the VAPAR.Solutions platform leverages cloud computing and its AI engine to automatically assess inspection videos that users upload. The platform is accessed via any web browser where videos can be uploaded, analysed, manually audited by an expert (if required), with a report generated and stored, eliminating the need for hard drives to back up the video data and corresponding reports.

With this approach, both asset owners and CCTV contractors are reducing the time taken for assessments, standardising the process to remove any subjectivity and utilising AI to deep dive into the data to get better outcomes.

In 2020, VAPAR worked with asset owners in Victoria, Australia, where the results showed that the solution outperformed the same inspection carried out manually. The AI algorithm missed fewer defects and was more accurate in grading the pipes. To date, VAPAR has processed over 3 million images, which means the AI has only become quicker and more accurate.

Industry impact

With the need for the pipe network needing special attention, technology is adding another lens to take a closer look. It’s empowering engineers, operators, and decision-makers to make data driven decisions more cost effectively and proficiently.

Read more about our case studies here: CASE STUDIES

sewer overflow

Sewer Blockage – What causes it and how to get it cleared?

Sewer Blockage – What causes it and how to get it cleared?

Image of sewer overflow due to blockage

Dry weather sewer overflows caused by blockages can create significant issues for utility providers, the community, and the environment. What are some of the reasons sewer/wastewater pipes become blocked?

Tree roots

The number one cause of sewer blockages in most networks is tree roots.1 In addition to sunlight and carbon dioxide, trees require water and nutrients to grow and survive. The consistent flow through sewer pipes provides a rich and attractive source for trees. While the gravity pipe network would ideally be a closed system, there are numerous pipe joints and cracks where tree roots are able to squeeze through as they seek out nutrients. If enough of a gap exists, the root mass can become so large within the pipe that it can eventually block, causing a back-up of sewage flow and discharge at a point upstream. The point of discharge is commonly a sewer maintenance hole or house overflow relief gully. Dry weather overflows may persist for some time before being observed and reported for fixing.

FOG: fats, oils and grease

Another contributor to sewer blockages is FOG: fats, oils and grease. If you’ve ever wondered why you are asked not to pour these cooking by-products down the sink, this is the reason. Incorrectly managed trade waste from food establishments is also a significant contributor to FOG issues in a sewer network. These products increase the likelihood of a blocked sewer and overflow. Fats, oils, and grease can solidify after they cool and build-up on the inside of pipe walls, they have a tendency to coagulate with similar particles, or exacerbate already existing root intrusion issues, and can result in partial or complete blockage of a pipe. An internet search of ‘sewer fatbergs’ will provide graphical insight into the scale of the problem.

Foreign objects

A third cause of sewer overflows is the flushing of objects down the toilet that belong in the rubbish bin. The most recent offender on this list is wet wipes. While toilet paper is biodegradable and designed to break apart after flushing, wet wipes are not the same. This material interacts with both tree roots, fat deposits and other solid materials dramatically increasing the likelihood of blockages. Other common items that don’t belong in the sewer system and contribute to blockages include paper towels, sanitary items, condoms, hair, kitty litter, and cotton balls.

Other potential triggers for blockages in pipes are the build-up of sediment or broken pieces of pipe which reduce the cross-sectional area of a pipe and can lead to partial chokes and eventual blockage.

How are these defects identified during a CCTV inspection?

VAPAR uses artificial intelligence to automatically identify and categorise pipe defects including root intrusion, debris/deposits (incl. FOG build-up), and other obstructions within a pipe that can identify the potential risk of blockage. The VAPAR.Solutions platform provides defect level reporting that can be matched with historical work orders and blockage events to assist in pipe maintenance programs to reduce the risk of future blockages.

Image of sewer corrosion
  1. Sewer performance reporting: Factors that influence blockages (Marlow et al., 2011)
Inspection camera being lowered into sewer manhole for 3d digital examination

Top 5 technologies accelerating CCTV pipe inspection turnaround

Top 5 technologies accelerating CCTV pipe inspection turnaround

Inspection camera being lowered into sewer manhole for 3D digital examination

As the old adage goes, time is money. A significant amount of the cost for CCTV pipe inspections can be attributed to the equipment, site set-up, back office processing of deliverables and associated labour. The good news is there are new technologies available to CCTV contractors and asset owners alike that can be used to drive down the overall cost of the CCTV inspection process.

5G for cloud streaming and streamlined access to online tools

The pipe inspection process is a field-based task and has to happen wherever the pipe is located. Prior to the roll out of 5G, the transmission of large amounts of data (such as video data, network mapping data) to and from the inspection location was often time prohibitive. In Australia, with Telstra’s rollout of 5G many major city locations and some rural locations now have access to fast wireless data streaming services. We can expect to see many IoT (Internet of Things) and cloud streaming services being deployed in wastewater networks as the 5G coverage and adoption increases.

AI for advanced analytics

Artificial Intelligence (AI) comes in many shapes and sizes and can be utilised in multiple areas to aid the pipe inspection process. Not only are there applications like VAPAR’s that can automatically detect defects in pipes based on the inspection footage, but there are also statistical models that can predict pipe degradation, making the scoping of the next CCTV inspection package more targeted. AI has the potential to streamline both on-site activities as well as back-office activities, by taking out the manual parts of the inspection workflow.

APIs and integrations for data centralisation

Application Programming Interfaces or APIs are used to streamline data between different software tools (in particular, online software tools) without needing a person to manually export data from one system and format it or manually enter it into another system. 

When it comes to the pipe inspection and asset renewal process, there are many software tools involved. The process will typically start within an Asset Management System (or AMS) where pipes are selected for inspection. These pipes then need to be matched using a GIS system (Geographic Information System) so that operators know where underground the pipes are positioned, and how to gain access. Once the inspection data is captured, the results then require review before being entered back into GIS and AMS platforms.

The whole process can take several days, if not weeks, with different formats and spreadsheets and manual data entry required. Through the use of APIs, data being passed back and forth can be repeated and automated without the resource load and delay of having to manually match data in different systems each time.

There are a number of other uses for APIs in asset management given the number of different software tools that are involved in maintaining an asset throughout its lifecycle. 

Autonomous hardware control for finer movement

Many existing crawler systems have telemetry (movement) data available that is being under-utilised in the current method of capture. Building systems that use this data and either recommend or automate crawler movement can prevent the camera tipping and traction issues. Currently operators need to be very careful in their operation of crawler hardware and can risk losing the expensive camera gear in the pipe. Crawler manufacturers are looking for ways to utilise this telemetry data in a way that assists operators and speed up the capture process. The future of such technology, if paired with AI, could lead to fully autonomous inspections being carried out at a faster rate with lower risk to the hardware.

Computer vision

The concept of computer vision (CV) is to use the pixels in a digital image to better understand what is happening in the picture. Some common computer vision applications include edge detection and filtering “noise” from images. Computer vision can also be used to estimate measurements from an image and to track changes over a series of images. The combination of computer vision tools can be used to provide additional insights and estimation measurements within CCTV inspection footage. We may also see applications for CV that stitch images together to create a “street view” like rendering of pipes, creating a software alternative to the similar deliverables that can currently only be obtained using specialised 360 degree cameras.


There is so much innovation that is happening in the CCTV inspection space, and there are many companies that are pushing the boundaries. Talk to your clients and suppliers about how they can include some of the above industry innovations into their delivery process, and you might find some savings and additional value. 

For further information about how you can streamline your CCTV inspection process with AI read more here.

CCTV Truck1

How to capture AI-friendly Pipe Inspection Footage

How to capture AI-friendly Pipe Inspection Footage

As VAPAR’s CTO, it’s safe to say I’ve got a good familiarity with which inspection footage works well (and which doesn’t) for automated pipe inspections using artificial intelligence (AI).

Over the last few years, the capability of image recognition AI models have improved significantly, meaning automation is a universally serious time-saver for many organisations looking to optimise or streamline their image based assessments. 

Although accuracy of artificial intelligence has improved over this time, the results which AI models are able to produce can sometimes be limited by the characteristics of the inspection footage which they are fed. If Contractors are looking to maximise the results they can achieve for themselves and their clients using AI, there’s definitely some recommendations I’ve observed which should be followed.

As different AI vendors may have different ways of handling challenges and developing solutions. I’ve tried to cover each point with a generalist approach. Many of these challenges would also be true of a person trying to provide a condition assessment based on the footage alone.

Challenges and Limitations

Firstly, to get some better context around the recommendations, I’ll outline the main challenges and limitations of AI for automated CCTV coding I’ve observed during my time with VAPAR.


Generally, pipe inspection standards will define a number of codes to be used which require granular detail which is not reliably achievable for operators or software without quantitative computer vision and tracking of camera telemetry.

Sizing of Features

Determining the size of features within millimeter accuracy is a challenging task for software and human operators alike.

‘Clock’ Positioning

Using 12 segments (named to align with clock references) can be challenging depending on the amount of panning, tilting and zooming that the operator undertakes during the inspection.

Defects that look similar

There is a level of subjectivity in many of the inspection codes that are expected in the reports. If the inspection footage does not clearly show the issue, it is very hard for anyone reviewing it to produce an accurate report.

Start & Finish Nodes

Start nodes may not always be present in footage captured by CCTV contractors. Furthermore, the type of maintenance hole used to access pipes can be difficult for AI to ascertain. Inspection footage is typically started from the centreline of the maintenance hole pointed directly down the barrel of the pipe to be inspected. These nodes are typically evident to the CCTV operator as they require entry to perform the inspection. The other tricky thing about nodes is they often contain defects we would code in pipes, but would not code in the node (such as debris or cracking). I think more needs to be done around the inspection and reporting of node defects.

Continuous Defects

It can be difficult to determine whether defects are discrete or continuous when a CCTV camera is moving through a pipe. This is due to the capture of the defects jumping in and out of frame during camera operation (sometimes we see panning and tilting without the camera stopping).

Multiple Assets in a Single Video

Where a CCTV camera travels through more than one asset, AI will need a way of identifying this distinction and handling the condition assessment of the assets separately. Otherwise the defects detected would all be assumed to be part of a single pipe asset which is incorrect. It can be tricky to know if the node between 2 pipes is expected or unexpected, especially in locations where GIS does not have a full picture of the underground assets.

Multiple inspection time frames captured in a Single Video 

Where a camera operator approaches an issue that needs to be immediately resolved (such as a blockage), they can stop the recording of the footage, clear the issue, and resume recording again. Where the halted inspection footage and completed inspection footage for the same asset are in a single video, AI needs a way of identifying this distinction between previous or ‘abandoned’ footage vs.‘completed’, and then overriding the abandoned condition assessment with that of the completed footage.

Shape or Dimensions Change

Where pipe shape or dimensions change, quantifying the extent of this change can be difficult to determine when using visual inspection footage alone.

Smooth operator 🎵 (Smooth camera operation)

Not so much of an issue in standard pan/tilt/zoom footage, but in “push rod” footage where the speed of the camera moving affects the quality of the footage, it can give AI and human reviewers alike a headache when trying to review.

Poor visibility

Cleaning while capturing inspection footage can “mystify” the vision. We recommend cleaning first and then carrying out the inspection as, firstly, the inspection video is a lot shorter, and secondly, the defects are a lot easier to see in the pipe after cleaning. (There are also things that are less in operators control such as splashing from water inside the pipe and steam that make footage hard to review.)


Now that I’ve outlined the core problems we’ve encountered with AI for automated CCTV coding, let’s cover some tips to ensure you’re capturing AI-friendly pipe inspection footage:


There are a number of standard procedures that operators can apply to ensure inspection footage is optimised for use with AI pipe assessments. Areas where standardised procedure can be introduced to great effect are:

  • Standardising the asset information block at the start of footage capture (on-screen display)
  • Standardising the chainage on-screen display positioning.
  • Standardising a requirement for the CCTV camera head to be centered within the pipe and field of view also centered (to see equally the top and bottom of the pipe).


There are also a number of procedural restrictions which CCTV operators can observe in order to create footage optimised for AI-based pipe assessments. These include:

  • Restriction of cleaning during capture of inspection footage (i.e. CCTV capture during jetting, where the jetting head is visible throughout the footage and obscures the field of view) used for condition assessment.
  • Restriction on reversing significant distances through the pipe – this can cause offsets in the chainage measurement and also cause problems for the AI, which will duplicate the detection of defects and features.
  • Restriction on zooming whilst moving (either driving forward or panning), as this can make this camera movement difficult to track.
  • Restriction on stopping and starting the capture of footage within a single video, i.e. where cleaning is performed or the camera is moved without recording, the inspection should be taken in a single pass.

These recommendations are some of the main components we’ve identified that have the ability to impact the post processing of video files – either by AI or by an inspector.


What data says about service defects in sewer pipes (and how to prevent them)

What data says about service defects in sewer pipes (and how to prevent them)

Back in October, we published a blog outlining the most common structural defect types within sewer pipe infrastructure, according to a data set of around 30 km which we’d borrowed from footage in Australia, NZ and the UK.

Now, we’re rounding things out by providing the same information for service defects within sewer pipe infrastructure, using the same data set to provide unique, data-led insights about the most common service defects in sewer pipes, and how to prevent them.

About Service Defects

By way of background, service defects are those that have an impact on the operational capacity of a pipe, impairing the pipes effectiveness to convey wastewater through the pipe network. 

Compared to structural defects, service defects will not involve the structure of the pipe itself. Commonly observed service defects include displaced joints, debris or root intrusions.

A Quick Summary of Our Data Set

If you’re after a more comprehensive overview of the dataset we used, I’d definitely recommend checking out our previous blog on structural defects (that shared the same dataset) to get a complete picture. In this instance, I’ll just cover the key points to avoid bogging things down.

The data set we used consisted of 605 pieces of wastewater pipe inspection footage, representing 26.45 km in combined network length from Australia, NZ and the UK.

Concrete and vitrified clay were the most commonly observed pipe construction materials, representing 45.25% and 42.02% of the dataset respectively, flexible plastics represented 11.79%, and a miscellaneous ‘other’ covered a tiny 0.95% of materials.

A variety of pipe diameters were also identified; 150mm (6 inch) diameter was the most commonly found within the footage, followed by 225mm (9 inch) and 300mm (12 inch).

Shorter pipe chainages were more frequently observed than longer ones; the ‘0-20m’ chainage category forming just under a third of total results – combined with the ‘20-40m’ category, these two represented around 54% of our total data set. Chainages of over 100m were infrequently observed in the data set; with any chainage over 100m forming just 5% of the total observed chainages.

Defects – An Overview

Immediately, there’s a few clear key trends observable in the data set; occurrences of displaced joints and root intrusions are by far the two most common defect categories, with instances of lesser severity significantly more common than those of greater severity. In fact, instances of displaced joints were so common that they formed three of the top four most common service defects we observed.

A full breakdown of the defects we discovered can be seen in the treemap diagram below:

With the overarching trends spelt out, let’s dive a little deeper into the two most common classifications of defects that we’ve just discussed.

Displaced Joints

Firstly, it’s important to note that since WSA 05 2020 (Australia’s version of a conduit assessment code) was released, displaced joints are now classified as both structural and service defects. If you’re keen to learn about the changes that WSA 05 2020 brought, I’d highly recommend reading another blog we released in September which outlines the most important considerations on this topic.

Looking into the data we collected, it’s clear that among service defects within sewer pipes, instances of displaced joints are king (perhaps instead, they should be labelled a royal pain!). Diving in a little deeper, instances of joint offset (sometimes referred to as ‘radial’ displacement) occur around 2.5 times as frequently as their joint separation (can also be referred to as ‘open’ joint) counterparts.

The prevalence of displaced joints within pipe infrastructure is most common in vitrified clay pipes, particularly older designs without rubber rings in joints. With our dataset including a high proportion of vitrified clay (42.02%, to be precise), there is a pretty clear correlation found in the defects we observed compared to the materials used in their pipes.


The other main service defect culprit which we identified within the data set was that of fine root intrusion, which was the second-most observed defect category.

Similar to displaced joints, the prevalence of root intrusions won’t be any great surprise to anyone who deals with sewer pipes day-to-day; they’re a constant thorn in our side!

From our data set, we observed that the majority of fine roots intruding into sewer pipes entered the pipe through the joints. This suggests that implementing better pipe sealing could act as a remedy to regular incursions of fine roots.

A study undertaken by University of Melbourne outlined the most common factors causing greater frequency of root invasions, those being tree proximity, tree maturity, tree type, soil type, and temperature/evaporation rates. The study found that “blockages occurred most frequently when temperatures and evaporation were at their lowest, i.e., August to October.”

The study also investigates the efficacy of both chemical and physical treatments to prevent root intrusion. The physical treatments included compaction and cement slurry, both of which showed quite promising results in inhibiting root growth compared to their chemical counterparts – which I found particularly interesting. The study attributes the effectiveness of the cement treatment to “increasing soil strength above the force that the roots were able to exert”.

What can be done to prevent these defects?

Joint Displacement

Although there’s no silver bullet solution to prevent joint displacement, there are a few ways that asset owners can limit the prevalence of displaced joints in their sewer pipe infrastructure.

The best time to take action to prevent displaced joints is prior to, or during the installation process. Adding spigot and socket (or similar) pipe joints and a flexible joint material into engineering specifications will help to maintain the water-tightness of the pipe even with some degree of inevitable joint articulation.

Additionally, during installation, ensuring that pipe bedding material has undergone a thorough level of compaction will help to prevent settlement or movements in these pipes over time.

Finally, when installing sewer pipes that have spigot and socket joints, drainlayers should ensure that pipes are pushed precisely to the witness mark. By implementing a careful approach during installation, asset owners will notice fewer cases of damaged pipe ends and rubber seals.

In instances where joint displacement has already been identified, more extensive works will generally be needed to address the issue. Depending on the severity of the defect, pipe relining may be required. In particularly severe instances, excavation and replacement of offending pipe sections may be the only solution.


Firstly, I’d like to point out that one of the most effective ways to minimise root intrusion into pipes is by minimising joint displacement in pipe networks. So, if you’ve implemented the advice directly above – you’re already halfway there!

The application of herbicidal foam in sewers is one of the leading solutions for reducing regrowth of roots that enter sewer pipes. I’d highly recommend checking out this video if you’ve never experienced how this process works.

There’s a trend which is seeing asset owners move away from root cutting as a solution to root-related defects, and with good reason. A great article from Newman Plumbing explains it brilliantly; “each time roots are cut they respond by regrowing thicker and faster, similar to pruning a hedge. The aggressive nature of the cutting process will also damage the condition of the pipe and will inevitably result in costly rehabilitation or replacement.” Many asset owners seem to be in agreement, and are moving towards other means such as herbicides so as to minimize the impact of repairs on their pipe infrastructure. 

For particularly problematic sections of sewer pipe, relining the complete asset may be necessary so as to remove the opportunity for the roots to reach water via the joints.


That’s all, folks! If you haven’t already seen them, check out our other blogs on structural defects in sewer pipes, and defects in stormwater pipes.

Sewer Blog Image V2

Why do sewer pipes break? Here’s what the data actually says.

Why do sewer pipes break? Here’s what the data actually says

In May, VAPAR completed a data-dive to check out the most common defects found in stormwater pipe infrastructure. More importantly, we provided recommendations based on this data to help asset owners to reduce the risk of defects developing.

Last time, we noted that our stormwater CCTV footage inspections unearthed patterns of defects according to the material used to construct the pipe. This was a great development, since an element of predictability gives asset owners the chance to take informed action during their design and construction process to mitigate the risk of defects occurring down the line.

At the time of publication, I’d promised to deliver a similar piece relating to sewer pipe infrastructure. This time around, I’ll be breaking my analysis down into two parts – one with data and recommendations around structural defects (you’re reading it now!) and one around service defects (which will be released soon).

Defects in Sewer Pipes vs Stormwater Pipes

Before we get stuck in, I’ll just clarify a few points for any non-engineers who might be reading – there’s some differences between wastewater and stormwater pipes.

Sewer pipes and stormwater pipes mainly differ due to:


In urban areas, all properties need wastewater connections, which will generally (on average) start at 150 mm (6 inch) in diameter. 

Conversely, stormwater pipes are only used when overland flow depths in kerb profiles exceed the allowable, in which case a pipe should be installed. These pipes need to carry a larger capacity from the upstream point, generally (on average) starting at 300 mm (12 inch) in diameter.

Pipe Material

Because sewer pipes are ubiquitous, reasonably priced and readily-accessible pipe materials are most commonly sought for installation. This means that wastewater pipes will more frequently be made of materials such as PVC or vitrified clay than stormwater pipes.

On the other hand, since stormwater pipes are typically of larger diameter (and therefore demand greater reinforcement), more expensive materials such as concrete will be used for installation more frequently.


It’s also commonly noted that sewer pipes will generally contain less debris (street litter, leaves, branches) than their stormwater counterparts. However, because wastewater pipes are typically smaller in diameter, always flowing, and have more lateral connection/junction points, there’s a greater comparative risk of blockage.

In most cases, wastewater network odours are managed through controlled venting of the system. This can reduce the rate of pipe degradation, however the chemical and biological composition of wastewater still means that design lives of between stormwater and wastewater can still greatly differ.

Snapshot – Our Dataset

We used 605 pieces of sewer pipe inspection footage, representing 26.45 km in combined network length as our dataset for our investigation. 

The footage had been uploaded to VAPAR’s cloud platform by VAPAR clients over the last few months for automated analysis, and was sourced from clients located in Australia, New Zealand and the UK.

A Breakdown of our Dataset

Material Types

From the footage which we used, concrete and vitrified clay were by far the most commonly identified construction materials, representing 45.25% and 42.02% of the dataset, respectively.

The third most common material present was flexible plastic (11.79%), whilst a miscellaneous the ‘other’ category encompassed just 0.95% of materials.

Vitrified clay is a very common material type for pipes of smaller diameters. As mentioned earlier, the ubiquitous nature of sewer pipes make it an ideal material for installation – vitrified clay is a natural material, and is readily available in many countries. 

Moving into the larger wastewater pipe diameters, concrete will more commonly be used as a construction material due to the increased reinforcement demands larger diameters impose. For the purpose of this blog, I have defined concrete construction to encompass steel reinforced (SR), fibre reinforced (FR) and asbestos cement – although strictly speaking these don’t have the same structural attributes as each other.

Plastic pipe construction is the ‘up and comer’ amongst wastewater materials. Plastic construction is becoming more and more prevalent as the material behaviour is becoming better understood by asset owners.

Pipe Diameters

A variety of pipe diameters were also identified; 150mm (6 inch) diameter was the most commonly found within the footage, followed by 225mm (9 inch) and 300mm (12 inch).

From a logical perspective, the spread of pipe diameters in our dataset makes a lot of sense, and absolutely aligns with my expectations of a typical wastewater network. Pipe of smaller diameters connect to properties everywhere, and are the most common diameter; these in turn feed into increasingly larger pipe diameters deeper into the network. As we move deeper and deeper into a wastewater network, we can expect the pipe diameters to increase, with their frequency to decrease accordingly.


Within the dataset, shorter pipe chainages were more frequently observed than longer ones; the ‘0-20m’ chainage category forming just under a third of total results – combined with the ‘20-40m’ category, these two formed around 54% of our total data set.

Chainages of over 100m were infrequently observed in the data set; with any chainage over 100m forming just 5% of the total observed chainages.

Again, the distribution of this data makes perfect sense given the context of a sewer network. Because sewer pipes are so ubiquitous, there are large numbers of pipes connecting properties to mains, meaning that networks of mains pipes change direction frequently to facilitate connectivity.

Structural vs Service Defects – What’s the Difference?

Before we dive in, I’ll quickly clear up the difference between structural defects compared to service defects.

A structural defect is one which has an impact on the structural integrity of the pipe itself. Over time, structural defects may worsen significantly to the point that the pipe requires significant repair work, or even replacement. Common structural defects could include cracking, breaking, or surface damage.

Service defects are those that have an impact on the operational capacity of a pipe, impairing the pipes effectiveness to convey wastewater through the pipe network. Common service defects include displaced joints, debris or root intrusions.

In this edition, we’ll be covering structural defects encountered in wastewater pipe infrastructure. We’ll release the results for service defects in the next edition of our blog.

Structural Defects

Combined Results

Overall, minor instances of longitudinal cracking was the most commonly observed defect from the dataset, representing one of the three most common defect classifications across all material types. 

Similarly, minor instances of circumferential cracking was also highly represented, also present in the top three defect categories across all pipe materials.

Surface damage (aggregate exposed) and minor instances of multiple cracks were the other main defect culprits our platform recognized.

A full breakdown of combined structural defects across all pipe types is below:

Small cracks and exposed aggregate formed the most common defect types within our data set, which makes logical sense. Both of these defect classifications are most common amongst concrete pipes, which were the most prevalent in our data set, making up 45.25% of the total material observed. 

Over time, and with changes in the pipe environment, these types of defects would continue to degrade, eventually progressing to more severe defects which could have meaningful interruptions on wastewater service to the areas they service.

Since it’s difficult to make informed recommendations from this data without specific contextual parameters, we decided to separate our defect analysis by pipe material type to identify clearer patterns and trends.

Defects by Pipe Material


Surface damage (aggregate exposed) was the most frequently discovered defect found within pipes of concrete construction. Minor instances of circumferential cracking and longitudinal cracking were also present in concrete pipes, whilst surface damage caused by corrosion was also prevalent in the dataset.

A full breakdown of defects found in concrete pipe is below:

The results gleaned from our concrete pipes are extremely interesting, and supports the typical engineering hypothesis of failure modes from surface related defects. 

Once concrete aggregate has been exposed from initial surface damage, corrosion becomes more prevalent – with concrete cover reducing, steel reinforcements become exposed to air and moisture, causing them to corrode. Corrosion products will then leach out of any cracks or fissures in the concrete cover, resulting in spalling of the concrete cover.

Although cracking is prevalent in the dataset, it is on aggregate less prevalent than what we would see in other rigid pipe materials (i.e. vitrified clay) due to the structural reinforcement. 

Circumferential cracking may suggest angular movement of the pipe (relative to the pipe central axis), potentially caused by ground movement over time or poor bedding compaction. 

Longitudinal cracking (especially at the 12, 3, 6 and 9 o’clock positions) can suggest that design loads have been exceeded. 

I will note that this data includes other types of concrete/cement materials, which may impact the results.

Vitrified Clay

It’s not an exaggeration to say that if you’ve got a defect within a vitrified clay pipe, far more often than not, there’s going to be cracking involved.

Minor longitudinal cracks, minor circumferential cracks, and minor multiple cracks were the most common defect that the VAPAR platform picked up in pipes of this material. More severe longitudinal cracking, multiple cracking and circumferential cracking were the next most common defects observed.

Again, a full breakdown of defects within vitrified clay pipes is below:

Unlike concrete, vitrified clay pipes are not reinforced, so longitudinal, circumferential and multiple cracking are perfectly normal (and expected) defects for this material type.

Some progression in the severity of cracks is evident; whilst smaller cracks are the most evident defects for vitrified clay pipes, there is still a sizable (albeit smaller) representation of large cracks too.

In case you were interested in finding out a little more about the vitrified clay vs earthenware, I would definitely recommend this excellent piece provided by Jonathan Morris of Opus International Consultants (Wellington).

Flexible Plastics

Cracks again dominated the most frequently observed defects within pipes made with flexible plastics, taking out five of the six most frequent defect causes.

However, they didn’t take out the top spot, which went to minor instances of deformation (severity less than 5%) – no great surprise given the flexible nature of plastic construction.

Below are the defect results for flexible plastic pipes:

There’s a growing sentiment that using plastics for pipe construction is the way forward for asset owners. 

A study conducted on 4 different pipe materials (concrete, polyvinyl chloride (PVC), vitrified clay, and ductile iron) suggested that “that PVC pipe is the most sustainable option from both environmental and economic viewpoints”. I’m personally interested to see how this unfolds across the industry.

How can good planning and design help avoid impactful structural defects?

A common theme that we’ve observed is that the majority of more impactful defects (i.e., those that are more severe) generally stem from degradation of initially minor issues.

Asset owners should log instances of minor defects, and assess other factors that could potentially affect the degradation of the asset. This will allow for an informed, effective reinspection plan to be established in order to monitor the progression of defects, and prevent major, impactful structural issues to infrastructure.

Asset owners should also make an effort to observe the technical specification of their pipe construction materials. By doing this, they will be able to make informed, data-driven decisions when evaluating the contents of their asset management plans, ensuring that pipe infrastructure is allocated an appropriate amount of resources and attention.


That’s all, folks! We’ll be releasing similar information relating to service defects soon in an upcoming blog, so stay tuned.

We are now a SWAN member!

We are proud to announce that we are now officially a member for SWAN – The Smart Water Networks Forum.

SWAN is a UK-based global hub for the smart water sector. It brings together leading international water utilities, solution providers, academics, investors, regulators, and other industry experts to accelerate the awareness and adoption of “smart,” data-driven solutions in water and wastewater networks worldwide. 

We are excited to be joining great water innovators.

Read more about our cases studies here