Sewer vent

Sewer Vents – The What, Where, and Why 

Sewer Vents – The What, Where, and Why

Sewer vent

Inspecting sewer vent

Transporting more than wastewater

The process of transporting wastewater from houses to treatment facility is a journey through pipes and pumps of various type and size. When designing and optimising the transport of this fluid, there is another key factor that must be considered by engineers – ventilation of the sewer network. 

As wastewater is pumped up and flows down through the different pipes in the system, there is also a movement of air. Due to the atmospheric pressure differentials at pump stations and within the headspace in the top half of gravity pipes, the network itself needs to breathe. The system must move air, as well as fluid.  

Why do we need sewer vents?

Venting of the wastewater network is important for several reasons, this includes: 

  • Providing airflow and pressure equalisation between the home and the pipe network 
  • Reducing and controlling odour issues above ground.
  • Avoid creating corrosive environments below ground that reduce asset life 

The ins and outs of vents

House vent – Otherwise known as a drainage waste vent (DWV) consisting of a 50mm (2”) PVC for a single dwelling and up to 200mm (8”) PVC for multiple dwellings, which extends above a roof of a building. This is usually installed at the head (furthest point from the main drain) of your property’s drainage system to allow enough air movement for you to flush your toilets and use all fixtures within your house and still maintain the water seals within each fixture 

Pump Station Vents (induct & educt) and Discharge manhole ventAt the pump station, a vent stack will also be present. This usually extends above the tree line, or nearby property roof level.  Vents are often constructed at the discharge points of the rising/forced mains. With wastewater being forced into the gravity system between two points, both locations need to have an open flow of air as from one end it draws in and the other it exhausts as the wastewater is displaced from one to the other.  

Diagrammatic representation of sewer ventilation

Image: Sewer Ventilation Clearance Requirements 

Forced ventilation (e.g., tunnels)Mechanical ventilation using a powered fan generates airflow at a controlled rate to ensure a sufficient volume of fresh air is circulated to ensure critical structures do not experience accelerated material corrosion. . 

Odour control units

In instances within sewer networks where odour is problematic, activated carbon filters can be used as a replacement for vent stacks. Vent stacks can become an occupational health and safety risk due to their deteriorating condition over their lifetime. Activated carbon neutralises gasses before they exit the vent pipe. In some cases, they are reducing odours up to 99%.  

There is a move to replace vent stacks due to ageing infrastructure and the risk they can pose to the public if they fail/collapse. An example of this is here, where a vent stack located near Muswellbrook High School (Australia) was replaced following ongoing odour complaints and the risk that it posed to the surrounding neighbourhood. 

Installing vent stack

Vent stack replacement. Muswellbrook High School, Australia (before and after)

There are several different options available to suit the needs of the situation. However, the principle is the same. Air flows in or out of the sewer through the replaceable filter media removing unpleasant odours without restricting the air requirements for the sewer to operate as intended.

Examples of types of vent replacement options.

These units ensure that harmful gasses within our sewer networks are ventilated and treated, helping keep us safe and extend the life of the underground assets for the utilities of your local area. 

About the author Anthony Woodhouse
Cloacina

This ancient roman sewer protected by a goddess! 

This ancient roman sewer is protected by a goddess!

Tiber river

Tiber River

Strolling along the Tiber River in Rome, you could be forgiven for missing this wastewater wonder of the ancient world. 

While there were many strollers and joggers along the neatly paved banks of the ancient river, my husband and I were bee-lining for our next stop on our Rome itinerary: Cloaca Maxima. 

What is Cloaca Maxima?

Cloaca Maxima is a large diameter drain built in Ancient Roman times in the 6th century BC.  The drainage structure was named after Cloacina, an ancient Roman deity that represented purification. A shrine to this deity was said to be near the original stream, which is said to be the inspiration for the name. The literal translation in Latin is ‘Greatest Sewer’. 

The design and construction

It was initially a stream that was lined with stone, aimed at draining the local marshes and removing waste from the city. By the 3rd century BC, it was enclosed with a stone barrel (semi-circular) vault so that the swampy land around the Roman sewers could be filled in.  

Cloaca Maxima Catchment area in Ancient Augustan Rome

Figure 1 Catchment area map created in 1886 of Cloaca Maxima in Ancient Augustan Rome (source: https://www.wikiwand.com/en/Cloaca_Maxima#Media/File:Roma_Plan.jpg) 

The sewer was said to be dimensions that allowed inspection boats and boats fully laden with hay to pass through. 

This post goes into more detail about the construction and history of the famous sewer for those that are keen to learn more: https://www.wikiwand.com/en/Cloaca_Maxima 

Cloaca Maxima today

Today, the sewer is still in use, though nothing more than a trickle comes out of the once ‘Greatest Sewer’, most likely groundwater, as the city’s sewage has been long diverted to more modern pipe systems.

Cloaca Maxima today

If you are looking to replicate this enviable photo opportunity, you can find Cloaca Maxima still visible where it joins the Tiber River near the Ponte Rotto and Ponte Palatino bridges. 

Lessons from the Ancient Romans

Whilst the sewer is still technically in operation today, its much-diminished role is reportedly due to the misuse of the sewer (people putting all sorts of solid waste down there, even some political execution victims!) and backflow from the Tiber. Over time the once ‘greatest sewer’ has been re-routed to more the modern sewer system that sends sewage to treatment plants for treatment before discharge.

It’s certainly interesting to see and learn about the challenges of legacy wastewater infrastructure. Design challenges such as back flow design can be accounted for with careful planning. Social challenges with sewer misuse can be accounted for with meaningful community awareness campaigns. Either way, engineers today are working to deal with similar challenges today, just manifested with a modern twist. 

About the author
Pipe jetting process

“What is Pipe Jetting and Everything You Need to Know About It”

Everything you Need to Know About Pipe Jetting

One of the common maintenance activities required to keep sewer and stormwater pipes flowing at full capacity is pipe jetting. Pipe networks are periodically inspected using CCTV cameras to understand the condition of pipes. Operational & Maintenance (or service) defects identified are an indicator that jetting may be required. The most common problems that jetters are used to fix are: 

  • Sediment build-up 
  • Fat, oil, and grease 
  • Tree root removal
  • Object blockages 

There are a wide range of jetting units available that are designed to suit specific tasks or pipe sizes. 

Pipe jetting process

Figure 1 – Pipe jetter in action

Hydro-Jetting Components 

The major components that form a jetting rig are: 

  • Engine 
  • Water tank 
  • Hose & reel 
  • Nozzle 

Depending on the size and power of a jetting unit, it may be: fitted to a truck/van/pick-up, trailer mounted, or be a small portable unit capable of accessing difficult locations. 

Jetting truck

Figure 2 – Jetting Truck

How do jetters work?

Jetters are commonly powered by a diesel engine, although there are also electric and gas-powered options available. The delivery of water to the nozzle is measured in pressure and flow. It is important to understand how these differ and can affect the success of the work at hand. In general, pressure provides the cutting power, and flow will provide the flushing power. The larger the pipe, the more powerful the engine required, and more water required to carry on-board.  

An example range of pressure and flow is listed below; you should contact your local distributor for advice on best options for your typical projects. 

Use 

Pressure 

Flow 

Smaller pipe jetting jobs. 

4000 PSI 

275 Bar 

5 Gallon/min  

20 Litre/min 

Typical all-rounder specification. 

4000 PSI 

275 Bar 

20 Gallon/min  

75 Litre/min 

High pressure output for more powerful cutting. 

5000 PSI 

345 Bar 

9 Gallon/min  

35 Litre/min 

Capable of clearing sediment build-up in larger pipes. 

2000 PSI 

140 Bar 

65 Gallon/min  

250 Litre/min 

Jetting is often completed in the upstream direction so that debris can flow back to the operator’s location, as well as minimising the risk of overflow behind blockages. The jetter nozzle uses the powerful spray of water to move along the pipe and completing the cutting/cleaning/flushing task required. There are hundreds of different nozzle designs on the market with the angle of spray from the nozzle defining if it is better suited to thrust/flushing or cutting/descaling.  

how jet stream works

Figure 3– The angle of jet stream to suit different performance criteria 

Nozzle Types and Accessories

There are standard nozzles designed to cover most circumstances, as well as specific nozzles and jetting accessories available. 

Switching Nozzle: The angle of spray can be adjusted while in the pipe from thrust (flushing) to cutting (descaling). 

Rotating Nozzle: Cleans full pipe surface. You may have seen stripes after cleaning where a fixed nozzle has not hit all parts of the pipe wall 

Sled Nozzles: Designed for heavy duty bottom sediment. Also called bottom cleaners, sledge, or sleigh nozzles. 

Camera Nozzle: Provides the ability to collect imagery from within the pipe while cleaning to collect condition data at the same time 

Debris Basket: Fitted at downstream point to collect debris and avoid secondary blockages after jetting. Also called drain traps, drain catchers.  

About the Author Mark Lee

Learn more about Sewer Network

VAPAR automates sewer and stormwater pipe condition assessment for councils, utilities and CCTV contractors.  Learn how we help improve the monitoring and maintenance of the underground pipes using AI.

Northumbrian Innovation Festival Sara Davies

VAPAR at Northumbrian Innovation Festival 2022

What I learned at the Northumbrian Innovation Festival

Author : Megan Clarkson

Representing team VAPAR, CEO Amanda Siqueira and myself headed to join the activities of the Northumbrian Water Innovation Festival, where the aim of this festival is to tackle community issues and encourage the collaboration of innovators to brainstorm solutions and pathways and tackle the pain points of the issues highlighted for the festival.

But before we get too deep into the problem-solving aspect of our sprint, here’s how our first morning kicked off.

Northumbrian Innovation Festival 2022

First Impressions

Walking into the venue, we were greeted by friendly faces, high energy and even a professional juggler, and after a much-needed coffee, we gathered into the main festival tent for our welcome. Singing golden oldies and lifting our spirits, the High Row Gospel Ensemble began the festival by setting the crowd at ease. However, Nigel Watson and Heidi Mottram brought us back to business and gave us some more insight as to what the theme of the festival is all about: Untapped Potential.

This festival aims to revolutionise the water industry by solving issues within areas such as climate change, population growth, affordability issues, customer service and environmental care driven by sprints of innovation. Collaboration is the key word, where members from different marketplaces have been invited to join and to bring different perspectives and different ideas and to try to push the boundaries as we work together and are encouraged to try to solve these issues.  Fortunately, after some motivational words by guest speaker Sara Davies from Dragon’s Den, we left for our sprint.

Northumbrian Innovation Festival Sara Davies

Sara Davies shared her inspiring story

HMS Sewer Sprint

We were invited to take part in the Team HMS Sewer sprint, sponsored by 1Spatial, and our first day was all about setting the scene: what is the problem and who does it affect?

From various speakers in the water industry, we were exposed to the issues resulting from the transition of public pipes becoming private; who now owns these pipes, and where are these pipes? The lack of clear pipe mapping to answer these questions have left water utilities wasting time on the job trying to find pipes, map them in the field and then try to figure out who has ownership of these pipes, and thus who fixes them?

After a day full of presentations, we wrapped up the afternoon with fun demonstrations of pipe inspections, sound tests and special CCTV equipment.

HMS Sewer Sprint

After some much needed rest, we were excited to tackle the issues we identified on day 1.

That’s where day two’s theme came in: how can we solve these issues? Amongst other supply chain providers, we spent the day showcasing our solutions in between creative activity breaks where we, VAPAR, alongside Minicam, shared our valuable insights and useful technology capabilities. To close the second day off in our sprint, we participated in what was called ‘Dragons’ Den’ questioning, where we got to answer questions sparked from our presentation. After many discussions, we ended the day by joining the rest of the festival in some networking.

Northumbrian Innovation Festival Day 2

Takeaways from the festival

The remainder of the week covered building the business case and thereafter conducting a technical discussion and developing the ideal solution. But the important take aways from this experience was showcasing how valuable it is when different sectors in the industry come together to solve problems that our communities are facing every day.

The Northumbrian Water Innovation Festival has set the bar high on how engaging conferences can be fun and informative whilst also creating an environment to meet new people, share different perspectives and showcase creative solutions.

Learn more about Sewer Network

VAPAR automates sewer and stormwater pipe condition assessment for councils, utilities and CCTV contractors.  Learn how we help improve the monitoring and maintenance of the underground pipes using AI.

Size of sewer ball

Lessons from Parisian Sewers – Sewer Balls

Lessons from Parisian Sewers – Sewer balls

Author : Amanda Siqueria

On a recent trip to Paris, I convinced my husband and in-laws to come with me on an adventure into the underworld. Enter the sights and sounds of the Paris Sewer Museum (Musée des Égouts de Paris). Ever since I had read about the museum in a book (‘An Underground Guide to Sewers’, but Stephen Halliday) I had wanted to go.  

Tunnel cross sections in Parisian Sewers

Learning about the different tunnel cross sections used in Parisian sewers, Source: Author

Paris Sewer Museum (Musée des Égouts de Paris)

The museum is attached to a working sewer station that lets visitors explore the evolution of this hidden French infrastructure. Let’s just say, it’s a 4D experience, the fourth dimension being ‘smell’. That said, there was so much to look at and learn that the initial ‘wall’ of the odour was soon forgotten.

Picture of a sewer ball

Our first encounter with the sewer ball, Source: Author

Sewer Balls

Out of all of the things that we saw, the artefact that stood out the most were the ‘sewer balls’. The giant balls made of iron or wood were used to clear debris from the large diameter sewer tunnels.

Size of sewer ball

Me and my best mate, Source: Author

Sewer ball design

A lot of the tunnels were designed to be ‘visitable’, I.e. to provide manual access to the structure for inspection and maintenance purposes. In tunnels where this access was not provided, these ‘sewer balls’ were used, most often in siphon and outfall parts of the network. The diameter of the balls was slightly smaller than the diameter of structure they were inserted into so that they would be able to pass through unobstructed.

Diagram of sewer ball

Diagram of sewer ball use in Parisian sewers, Source: Brochure from Musée des Égouts de Paris 

Their unique design allowed for a small gap between the ball and the base of the tunnel through which the backed-up wastewater passed at high pressure and flushed out the sediment in front like a jet of water. The ball was then removed from the end of the structure and cycled through the tunnel until the structure was cleared of debris.

Teams of sewermen in the 1920s using various apparatus for clearing the sewers. Note picture of the sewer ball being used. 

Source: Halliday, S 2019, An Underground Guide to Sewers, Thame & Hudson

Lessons from history

Visiting this sewer museum, we learned not only about the sewer balls, but also the many other feats of engineering that were applied to wastewater collection and treatment in Paris. Although the balls themselves are no longer in use, it was interesting to see many of the same challenges that modern wastewater networks have, also existed at the time the network was first constructed. In the case of silt and debris removal, manual and physical methods are still a big challenge in modern sewers. Hashtags like #binthewipe and #weirdthingsinpipes illuminate some stark examples of modern sewer misuse. The challenges continue to grow in number with the increasing number of wet wipes and other rag material entering the network.  Perhaps a sewer ball revival is on the horizon? Either way, it’s an interesting reminder of the ingenuity of engineers in solving problems, and the need for awareness raising when it comes to sewer misuse.



Learn more about Sewer Network

VAPAR automates sewer and stormwater pipe condition assessment for councils, utilities and CCTV contractors.  Learn how we help improve the monitoring and maintenance of the underground pipes using AI.

About the author
crack in sewer pipe

Common errors with manual pipe inspection coding, learn more

Common errors with manual pipe inspection coding

None of us is infallible. We all make mistakes. The fact that we are human means there is always a margin for error. In whatever we do.  

 If you are a commercial airline pilot, the room for error is just not there. Lives are at stake if you make a fundamental error. So, there are many aspects that come into play to ensure that risk is mitigated. 

Planes, of course, are highly automated these days; autopilot can navigate and land the plane and arguably is less likely to make an error than a human. But the human is essential. You cannot rely on computers to do everything, and the human must be there in case of an emergency. The recent history of Boeing’s 737 Max is an example of what happens when this does not happen. This is where the best training comes in. Not just one-off training, but regular training and review. Then, of course, are the checklists and manuals. Specific processes to go through in every event. 

Boeing 737 image

Although planes are now highly automated, human input is still an essential element. 

So how does this relate to the coding of pipes? Well, unlike planes, CCTV camera surveys are not yet fully automated. The reporting system still heavily relies on human input to generate a report. Of course, the information is only as good as what is put into the system by humans. 

With pipe coding systems (and there are several of them around the world, including MSCC5 and PACP), there are a set of rules to follow in each instance. Fairly straightforward, right? – Well, yes, if everyone is trained the same way and sees the same thing. But we are humans, and we not only make mistakes but also see things from different perspectives. 

What one might see may be different to another, and this becomes apparent when you look through vast amounts of reports and footage. 

So, what are some common misconceptions, errors, and mistakes humans make when interpreting CCTV recordings? 

Cracks vs Fractures

Without doubt the most common. What is the difference, and how can you tell? A crack is just a broken line visible on the pipe wall, be it circumferential or longitudinal. It will not be open or moved apart; the pipe is still in place. A fracture you can clearly see where the pipe is open on the pipe wall and shows a visible ‘black line’, pieces of the pipe are still in place. 

crack in sewer pipe

Can you tell the difference between a crack and a fracture or cracks <1mm or >1mm” in Australia? 

Pipe Material or Material Change

Many times, the pipe material is coded wrong or missed completely. Often where there is a material change midline it is missed, and many coders can’t tell the difference between certain materials. Common types that get mixed up are pitch fibre and cast iron as they are both dark and can be hard to see. The difference between Vitrified clay and PVC and concrete and asbestos cement. 

Getting the code wrong here could lead to the wrong repair specification or inappropriate recommendations. With pitch fibre, this could cause a longer-term issue if the presence of the material is not identified at an early stage in the survey process and will affect the choice of no dig repairs or excavations. 

Broken vs Hole

Another one we see a lot is the difference between a broken pipe and a hole in the pipe. People’s definitions are mixed up here and without the correct training and reference materials these are often miscoded. A broken pipe shows pieces of pipe that have moved from their original place but are still there, whereas a hole is a visible hole in the fabric of the pipe with the pieces missing. 

 The broken pipe may need to be removed, whereas a hole has already gone. It may be necessary to recover the evidence. If this is coded wrongly then further work required may not be correctly identified, leading to further blockages. 

Junction or Connection

Lots of coders will confuse junctions with connections. The definition of a junction is one that is performed or purpose-made and built into the sewer. A connection, however, has been added afterwards, usually with a boss or just smashed into the pipe, causing a defect. 

 Junctions are meant to be there. If they are wrongly coded as connections, a recommendation may be made to remove and replace them when it’s not needed. Leading to costly, unnecessary excavations. 

Deposits

Attached or settled, fine or course, grease, or encrustation. All areas where easy mistakes can happen. Encrustation is often coded as grease and vice versa.

So, what is the difference between grease and encrustation? The easiest way to remember is that grease is essential ‘man-made’ whereas encrustation is usually mineral deposits caused by nature. These are usually attached to the pipe. 

 Deposits can cause flow issues, blockages and reduction in hydraulic capacity in the pipe and these foreign materials can stick to the inner pipe wall and become relatively permanent. 

 Settled deposits can be fine (DE S) like sand or silt or coarse (DE R) like gravel or rubble. There are plenty of descriptor codes in this category which often leads to confusion and if in doubt the code (DS Z) is a catch-all for all deposits that can’t be classified by the other codes. 

 Getting the type of deposit right is important because it will build a case as to what the issue with the pipe is. The evidence is important, especially if the pipe is being abused with grease and fat. If it is coded wrongly, the correct action may not be taken where needed. 

Clock references

There are often errors in clock references. Either when inputting a ‘to and from’ or a specific point (and determining when its required). Also, the actual clock reference itself. One person’s 7 o’clock is another’s 8. 

Getting the position wrong could affect where patches are installed or how it affects the serviceability of the pipe. A hole at 11 o’clock is not so damaging as a hole at 7 o’clock if the pipe is running at half bore. 

sewer pipe junction

A junction at 3 o’clock or is that 4 o’clock? 

Percentages

Used for several codes, percentages, like clock references, are open to human interpretation. Used in deformation, cross-sectional loss, and water levels these are often under or overestimated and not accurate.  

The extent of the intrusion or root mass or the water level is important to determine remedial action and the timescale. If cross-section loss is estimated at 50% when it’s only 20% this could overplay the urgency. 

Summary

So, can AI and automation, like the functionality provided by VAPAR,  help with these errors?  

Of course, the answer is yes! Setting out and agreeing on the exact parameters which define a code can allow the software to take out the subjectivity. Although, like a human, an AI will not be 100% accurate, 100% of the time. This is where the provision of a targeted human check of the AI outputs allows the accuracy to exceed using just the AI or Human capability. This approach is no different to how an airline pilot would use manuals and checklists on a plane to ensure the automated systems are working as intended. 

Of course, we are not dealing with hundreds of lives on a plane here, and these types of errors will not necessarily cause a catastrophic consequence. However, the pipe inspection coding errors in extreme cases can lead to the internal flooding of someone’s property or the pollution of a nearby water course.  A Combined Intelligence model, like that used by VAPAR, effectively merges the AI and human inputs to minimise mistakes, improve both accuracy and consistency, and generate efficiencies by grading pipes appropriately to be used in the asset management of piped networks. 

This article is Co-Authored by Nathan & Anthony

Learn more about Sewer Network

VAPAR automates sewer and stormwater pipe condition assessment for councils, utilities and CCTV contractors.  Learn how we help improve the monitoring and maintenance of the underground pipes using AI.

Manhole

What is a Manhole, and What are the Parts of a Manhole?

Access and Maintenance of Sewers: Manholes

What is a Manhole?

Manholes, maintenance holes, sewer access points, sewer access chambers……. the list to describe them can be endless.  Regardless of what they’re called, let’s take a look inside them and what their basic function is? 

Manhole

These are the assets that provide a surface connection to the underground sewer network below. Manholes split gravity sewer mains at regular intervals, often at changes in direction.  Their primary function is to provide access to pipes for cleaning, removing blockages, and allow condition assessment inspections by maintenance crews. 

Within the manhole there are a range of sub-components; it’s much more than just a hole. So now we know the basics, let’s jump in (not literally). 

Parts of a Manhole

Parts of manhole

Manhole Cover and Ring 

Generally round and constructed from cast iron with a concrete inset, the cover sits tightly inside the ring with the intention of creating an airtight seal to stop odours escaping, and surface inflow entering. In most cases, the cover should be flush with the surrounding ground surface level. 

Ladder/Step Irons 

Typically made from steel, although more recently non-corrosive materials, step irons are installed to enable maintenance personnel to climb down. In some cases, these are being removed, or not installed in new builds due to safety implications with workers lowered in using dedicated confined space entry equipment. 

Cone/Straight Back Taper 

Located just under the cover there is a taper or cone increasing in diameter to transition the internal diameter to a larger size at the sub-surface level. 

Cross section of manhole

Shaft/Chamber 

Below the taper, sits the shaft. This leads down to the base of the manhole. In significantly deeper manholes there will be a notable separation between the shaft and chamber. The diameter of the shaft varies between 1m to 1.8m.

Bench/Table 

This is a flatter concrete surface prepared with the intention of providing an area where maintenance crew can position themselves and stand within the manhole above the pipe to perform any tasks that are required .

Channel/Chase 

The channel is located at the center of the benching and is where the sewage/wastewater flows through the manhole. 

Invert 

The invert is located within the channel and is the lowest part of the manhole. It is a crucial level which is set with reference to a specific datum, specifically to allow the water to flow by gravity to its intended location. 

Inlet/Outlet 

These are the flow entry and exit points of the manhole. There can be multiple inlets to the manhole but almost always only one outlet. In special instances a bifurcation manhole may be installed that splits the flow into separate downstream pipes. 

Location of Manholes 

Their locations can vary from in the roadway, within properties and almost anywhere that sewer pipes are located (which some of the time isn’t the most practical). With relation to the sewer network, they are generally located at changes in direction, grade/slope, invert level or intersection of another sewer branch. 

About the Author - Anthony Woodhouse

Learn more about Sewer Network

VAPAR automates sewer and stormwater pipe condition assessment for councils, utilities and CCTV contractors.  Learn how we help improve the monitoring and maintenance of the underground pipes using AI.

Patch repair needed in new pipe

Streamlining CCTV Pipe Acceptance Testing

Streamlining CCTV Pipe Acceptance Testing

What is a pipe acceptance test?

Utilities that manage sewer and stormwater networks increasingly have reticulation pipework extensions constructed by contractors as part of developer works. These pipes are commissioned and adopted by the utility. In many cases, the new pipes are built as part of a larger development that incorporates road, footpath, and lot divisions for sale. It is important for public utilities to have assurance that these new pipe assets have been constructed to their approved design and are defect free prior to them taking ownership.

This inspection, or CCTV acceptance test, is a critical part of the process that confirms the newly constructed pipe meets the requirements set out by the relevant authority. A CCTV inspection for acceptance is intended to focus on a range of areas, including:

  • Surface damage of internal surfaces
  • Cracking, breaking, or holes in the pipe wall
  • Obstructions or deposits within the pipe
  • Constructed grade (fall) of the pipe
  • Deformation
  • Joint defects
  • Ponding of water, or flat sections
  • Connection and junctions
  • Length of constructed pipe

Public utilities usually specify that these inspections be completed to the relevant inspection reporting code and must meet minimum standards to be approved for contributed asset handover.

Patch repair needed in new pipe

Figure 1- Cured-in-place patch to rectify a pipe defect in a new pipe

Who completes and approves an acceptance test?

Civil construction companies are usually required to engage an independent CCTV sub-contractor to complete an acceptance test, with a qualified engineer providing sign-off on the CCTV results and other accompanying reports where required.

When does the acceptance test occur?

Utilities may be descriptive around what stage the acceptance test can occur, with practical completion of various other on-site works a pre-requirement. Where specified, this detail is listed in a specification document or instruction issued directly from the approving authority.

Cause of Delays

Delays in the workflow when submitting acceptance inspections can occur due to:

  • The time it takes to supply the approving authority the specified video and associated report/s; or
  • In instances where a pipe does not pass the acceptance test, there will likely be some form of minor repair/maintenance required and a follow-up CCTV inspection to confirm any identified issues have been rectified. In most cases this will be jetting to remove construction debris/deposits, or patching a location with pipe wall damage

If the follow-up to a failed CCTV acceptance test is delayed due to the workflow that is setup between civil contractor, CCTV contractor, and reviewing engineer; the cost to the overall project can be significant. In some cases, this delay will fall on the critical path of other finalization works and negatively impact other teams working on the development project. VAPAR has specifically designed a workflow that ensures the time between the CCTV inspection and approval is minimized to reduce any unnecessary or costly delays. In instances that repair or maintenance is required, the details of this can be distributed to the required parties quickly.

deposits and debris in pipe

Figure 2- Deposits and debris that requires removal before acceptance

How can VAPAR assist in avoiding costly delays in your review and approval timeline?

Same day turn-around can be achieved with upload from site that only requires the video file and an internet connection to your internet browser. VAPAR’s AI processing time is measured in minutes, not days. Your reviewed inspection results can be shared in real time with clients you have invited into the VAPAR.Solutions platform in a structured library of current and past inspection projects.

Alternatively, you can choose to send your package of inspection results for the day, or week, as a pdf report set or spreadsheet summary. What does this mean in practical terms? Data and results (including access to the selected inspection video files) can be shared without the requirement for downloaded software or file sharing programs. The CCTV inspection videos, and associated results are available directly to your client in the method most convenient for your situation.

Keeping all your inspections organised and accessible

VAPAR’s cloud storage solution for inspections means cataloguing, finding, and viewing your past CCTV results is both user friendly, and eliminates the requirement for on-premises storage. No more lost files spread across different servers and cluttered folder structures. For utilities that would like to compare original acceptance inspections with end of defect-liability inspection, or condition assessment years down the line, this can be done directly from your internet browser by searching asset ID, or node, to bring up your matching results.

Image of VAPAR.Solutions

Figure 3- Searching past inspections of the same pipe asset

About the Author Mark Lee
waste water monitoring

Increasing the value of wastewater network monitoring

Increasing the value of wastewater network monitoring

Innovation is the key to delivering ever-increasing performance

Asset owners around the world are looking for innovative ways to deliver on the challenge of increasing wastewater network performance targets. With improved technology and the ability to handle large amounts of data, it’s become significantly easier to monitor flow and depth patterns, and highlight issues within a network that trigger a maintenance response prior to a flooding or pollution incident occuring.

waste water monitoring

Radar level and IoT telemetry device from Metasphere (Sense Level, ART Sewer)
Wastewater monitoring can generate a return on investment when they prevent flooding and pollution incidents.

Of course, there is no point in installing monitors for the sake of it, they should be positioned so that they have the greatest value. Having monitors in areas that don’t generate a return on investment is not prudent, therefore knowledge of current system performance and planning is required to determine the optimal locations that will provide a positive return when installed in locations that are most likely to prevent flooding or pollution incidents. 

The most important part of the puzzle in locating monitors is to understand the characteristics of the most common failures within the network; blockages. A previous UKWIR project  identified the following: 

  • 20% of blockages reported over a year are repeats at property level and this increases to between 40% and 60% when analysed at the postcode level. 
  • The proportion of repeats increases to 30% and 70% at a property and postcode resolution respectively when there are 5 years of data available. 
  • Approximately 50% of postcodes and 4% of properties have suffered 1 or more blockages over a 9-year period, this reduces to 23% of postcodes and 1.2% of properties suffering repeat blockages over the same period. 
Picture of sewer blockage

Analysis of historic blockage data indicates blockages repeat at the same location over time.

This analysis shows repeat blockages happen at the same location and that if monitors are located correctly, they can be effective in preventing major incidents. 

 The report also identified the most common causes of blockages: high density of interceptors, high densities of FOG (fats. oils & grease) generating properties, older properties, terraced / high rise properties, small diameter sewers and lower affluence. 

 This suggests that taking remedial action such as removing interceptors, root cutting, repairing structural defects and educating customers about the use of FOGs and wet wipes would mitigate the probability of repeat blockages. Fixing the root cause will prevent having to constantly reattend to carry out blockage clearance maintenance, which causes inconvenience for the customers and increases operational costs. 

 In a perfect world asset owners would repair and replace all the defects in a wastewater network. The reality of course is there is no bottomless pit of money for this activity and funding will continue to be challenged given the current focus on the affordability of utility bills.  

Person calculating his expenses

The affordability challenge associated with utility bills means there will never be sufficient funding to repair all defects on the network.

Repairs are not always practical or cost effective

This is where asset management comes in and provides us with the capability to effectively balance the cost, risk and performance triangle depending on the objectives of the asset owner. For example, In the case of complicated wastewater networks that may run beneath buildings with a flat gradient that increases the blockage probability, then the implementation of a proactive cleansing programme is likely the best approach to balance cost, risk and performance.  The use of monitoring in these situations allows the proactive maintenance costs to be optimised and ensure cleansing is only completed when it is required. 

Cost, risk and performance triangle

Asset Management provides the capability to balance the cost, risk and performance triangle to deliver the asset owner’s objectives.

Alternatively, the installation of a monitor where roots have been identified or where a partial collapse has occurred is unlikely to balance the triangle correctly. It will likely be more efficient to mitigate the root cause (e.g. cut out the roots or repair the collapse) compared to monitoring the location.  

Data is key to making informed decisions

The ability to adapt the correct balance of cost, risk and performance for each scenario is based on having the right data available to understand the root cause of a flooding or pollution location.  Using CCTV pipe inspection data provides the ability to understand the root cause and enables monitors to be installed at locations where they can generate the greatest Return on Investment (ROI).  The historic challenges with CCTV pipe inspection data have been its cost (e.g. it is not cost-effective to survey the entire network) and the ability to provide the outputs in a format that allows good investment decisions. 

 VAPAR uniquely combines Artificial Intelligence, the latest software capability and human input, reducing the cost of CCTV pipe inspections and making the outputs more accessible to decision-makers. Reducing the cost of CCTV pipe inspections makes it more economical to either complete CCTV pipe inspections prior to installing a monitor or use existing inspection data as part of the monitoring decision-making process. A great example of making the CCTV pipe inspection data more accessible is the visualisation of the survey results via a GIS, where the defect locations can be understood relative to the proposed monitor location on the pipe network. 

Pipe network and defects seen on GIS using VAPAR

VAPAR’s capability to visualise CCTV pipe inspection data allows monitoring locations to be identified that will deliver the greatest ROI.

Conclusion

It is fundamental for Asset Managers to look at alternate and innovative ways of managing pipe networks if they are to deliver the increasingly challenging financial and performance targets. The use of network monitoring provides one of these innovative ways, however, it will not provide a ‘Silver Bullet’ in isolation.  The use of VAPAR alongside monitoring will allow CCTV pipe inspection data to inform the decision-making process on where to install monitors. Ultimately this will balance cost, risk and performance and ensure the return on investment from monitoring is realised. 

Nathan Muggeridge - Author
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Local Sewer History Finds

Local Sewer History Finds

Keeping an eye out for local sewer history finds

Most major cities had their first sewer infrastructure constructed centuries ago. While much of the original networks are either long gone or buried deep underground, if you do a little research and keep your eyes open you’ll likely find some interesting structures that formed part of the original systems. In some cases, these will be decommissioned, others are still in services hundreds of years after they were built.

Sewer aqueduct spanning Johnstone's Creek (Annandale, Sydney)

Finding a piece of Sydney’s sewer history

Out on a recent morning jog in Annandale, I came across a sewer aqueduct that was partially enveloped by the canopy of a large fig tree. Reading the faded plaque on one of the concrete arch supports and reading up on its history, it was interesting to learn about the important role this structure played in the early Sydney sewer network.

The Johnstone's Creek Aqueduct

Designed by Prussian engineer William Baltzer and constructed by Carter, Gummow and Forest in 1896, the aqueduct contains 8 primary arches and has a total length of 281m. It was the first use of reinforced concrete for a large structure in Australia. This very new construction technique of the time was under patent and known as the Monier system. The historical significance of the Johnstone’s Creek aqueduct has led to it being listed on the NSW State Heritage Register.

 

Early example of reinforced concrete in Australia

Transporting sewage to Bondi

The separation of the Sydney’s combined stormwater and sewer pipework began in 1887, and by 1889 the Sydney sewer network had reached 140km of pipe and was servicing close to 25,000 properties across the inner city. With this flow discharging into the harbour, construction of more sustainable options had been underway for some time. Construction of the Bondi Ocean Outfall and Botany Sewage Farm was completed in 1889 and allowed for further expansion of Sydney’s sewer network. 

This included the Northern Main Sewer which would service the growing population in Annandale and Balmain and transport flow to a main line junction at the corner of Parramatta Rd and City Rd, then all the way through to Bondi. This extension required crossing both Johnstone’s Creek and White’s Creek with the construction of aqueducts the most suitable design option of the time.

 

Could reinforced concrete be trusted?

In the late 19th century, the idea of using concrete for such a large structure was not without detractors. The original Public Works Department design called for a brick arch construction and the submission for this new design and material had initially been rejected due to its experimental nature and unproven history. However, support from Robert Hickson (Under-Secretary for Public Works) was interested in trialling the use of reinforced concrete and what was an innovative idea at the time. The Monier design delivered spans that could be 50% larger than brick, and the total cost of the project was quoted as 20% cheaper – it received the go-ahead for construction after test arches were loaded to failure at Burwood with positive results.

Looking west from Glebe to Annandale showing construction of Johnstons Creek Sewer Aqueduct. (City of Sydney Archives)

The rest is history

It didn’t take long before the advantages of reinforced concrete led to a rapid increase in use for a wide range of structures. The first reinforced concrete water reservoir was built in Kiama just a few years later in 1899. The Annandale Aqueduct has certainly stood the test of time, it required only minor maintenance in its first 90 years of service – far exceeding the 3-year guarantee period. The flume was eventually plastic lined in the 1980s and the arches underwent repair and protection works in 1996. 

Still interested in more of the aqueduct’s history?
Well, there was some controversy!

Like any good historical story, the construction was not without controversy. A Royal Commission was held in 1896 and ran for over a year. It was based around accusations of favouritism, contract violations, and defective work. This was not assisted by the fact that at the time William Baltzer suggested the alternate design he was working as a draughtsman in Sewerage Construction Branch of the Public Works Department while also on retainer as an engineer for Carter, Gummow and Forest who were awarded the contract. Despite the large furore and public investigation, the final report fully exonerated Hickson, Baltzer and others involved. It even went as far as finding that some of the allegations appeared frivolous and not founded in truth. As difficult as this must have been for the engineers and others involved in the commission so soon after construction, it is the detailed record of the commission that has provided such informative history and detail about the project from inspection to completion. It was the commission proceedings themselves that meant this significant construction achievement become one of the best documented contracts of the era.

Extract from the Public Works Inquiry Commission

VAPAR.Solutions is designed to process and score video footage from a wide variety of camera systems, providing a single cloud-hosted location for all your inspection videos, images, reports and decisions.

About the Author Mark Lee