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.

manhole cover in slovokia

Basics of Sewer Manholes

Basics of Sewer Manholes

Picture of sewer manhole

What are manholes?

Sewer manholes or also called maintenance holes are formal access points within the sewer pipe network that provide maintenance teams a chance to get access to maintain the sewer pipe network. They can come in many different shapes and sizes depending on how deep they go into the ground and what the surrounding ground conditions are like.

Why do you need manholes?

Once a blockage or a break in the sewer pipe is confirmed through a CCTV inspection, maintenance teams need to get access to remedy the issue. Without the presence of manholes, any remediation would be complicated and expensive.

Where can you find manholes?

The spacing of the manholes depends on a couple of factors. If a sewer pipe is running in a straight line in an area where access is not an issue, then they are usually placed every 80-100 metres (260-330 feet) along a sewer pipe. This spacing is determined by the practical length of water jetting equipment to reach the full length of pipe, regardless of whether the water jetting was done from the upstream manhole, or the downstream manhole.

That being said, manholes can also be built at shorter or longer lengths. For example, if the pipe needs to have bends in it, the design engineer might want to install extra manholes to account for the risk of blockage at the change point in the flow of sewage.

Manholes can also be placed within the network at irregular locations when the pipe network runs under a highly urbanised area. Placing manholes in the middle of roads, or in the middle of someone’s property is not advisable.

There are serious safety issues with placing manholes too close to live roads and having a manhole under a concrete floor slab doesn’t really serve anyone either. For this reason, the configuration of the network and the spacing of manholes might vary to account for the above ground infrastructure.

Drain spotting

You can identify the presence of manholes by the manhole covers on roads, footpaths and even in parks. The manhole covers themselves can come in many different shapes and sizes also, although most are round. They are usually made of metal to withstand the weight of heavy vehicles.

There is a great #drainspotting hashtag that you can browse to see what others have contributed from all over the world. Perhaps on your travels, you might feel compelled to contribute some interesting manhole designs and locations and help educate others on the weird and wonderful world of our underground sewer networks.

sewer points
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sewer overflow

What causes sewer blockage and how to get it cleared?

What causes sewer blockage 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)