managing expenses

How are sewer pipes inspected? 

How are sewer pipes inspected?

What is involved in a pipe inspection?

Most of the time required to undertake the inspection is dedicated to finding the access point and securing access. This means finding the right maintenance hole on either the upstream side of the pipe and the downstream side of the pipe. The surrounding areas near the access point must also be made safe and secure, as sometimes they are in roadway, foot paths or private property. Establishing the site is an important part of the inspection process so that there is no risk to the public and the workers involved in the inspection. Once the access point is located and the secured,then an inspection can begin.

An operator will lower the camera crawler into the pipe and remotely drive the camera along the length of the pipe, stopping to make notes of any faults or defects that they might find inside the pipe. They will continue this until they get to the end of the pipe. Once they get to the end, they will pull the camera back (the inspection cameras are usually tethered by a power and data cable) and return to the access point for retrieval.

Another aspect of a pipe inspection that takes time is the actual coding of the defects in the pipe. When the camera is inside the pipe, the trained operator must watch the video feed and identify and classify the type and location of the defect along the pipe.  

Sewer pipe inspection

What information does an inspection record?

Operators are trained to undertake this classification and quantification in alignment with their regional coding guidelines. These guidelines are used widely, and help to ensure consistency in understanding across organisations, stakeholders, and professionals. 

How can we increase the speed of inspections?

Some ways to increase the speed of an inspection is by implementing new hardware, new software, more effective training methods and materials, or by applying an improved process to inspections. Given that most of the inspection is concerned with locating the right asset and establishing the site, methods that make those processes more efficient would also have an impact on the turnaround of sewer pipe inspections. 

About the Author

Amanda Siqueira is an Australian civil and environmental engineer who has worked in design, construction and remediation of drainage and sewer pipes in Australia, New Zealand and the UK. She has passion for all things pipes and is also one of the Co-founders of VAPAR.

Experience the future of pipe condition assessments.

managing expenses

Why am I being charged for sewer? 

Why am I being charged for sewer?

Why am I being charged for sewer?

If your water authority is charging you for the capture, treatment and delivery of potable drinking water, then there is a high chance they are also charging you for the capture, treatment and discharge of wastewater. There are a number of processes that take place for water authorities to deliver these essential services to rate payers. If this service is not delivered well, there is an increase in risk to public health and the environment. 

managing expenses

What does the money go towards?

The primary functions of wastewater services is to collect, treat and discharge wastewater. The objective of any wastewater system is to do this in the most efficient manner that meets the public health and environmental goals of the community. This can be really challenging, as there are several technical and non-technical outcomes that need to be achieved. But at the heart of it, the system can be broken down into: 

  1. Collection systems- these are generally the pipes, manholes, trunk sewers, pumping stations etc.
  2. Storage systems- these are generally septic tanks, temporary storage tanks, etc. 
  3. Treatment/discharge systems- these are generally wastewater treatment/recycling facilities and discharge structures. 

Each of the above sub-systems needs to perform well in order to meet the public health and environmental goals of the community. There is an expense to keep these systems performing 24/7, and that is what the sewer charges go towards. 

wastewater management

How do the charges get applied?

Each water authority charges differently depending on the regulation and legislation in the region. For most water authorities, the charges are split up into fixed charges and variable charges, and the way they charge their customers often differs by customer type. Fixed charges are charges that customer pay on a regular basis (e.g. quarterly) for the fact that there is a connection into the public sewer system. Variable charges are charges based on a usage metric (e.g. per kilolitre or per hundred cubic feet). From what I have seen, most variable usage charges are applied to commercial and industrial customers, and less likely to apply to residential customers. The usage of residential customers is usually covered in the fixed charge. Because commercial and industrial wastewater discharge has a higher load of contaminants, there is a greater level of treatment complexity required that the water authorities have to account for, therefore levying an additional usage charge to cover the associated costs. 

About the Author

Amanda Siqueira is an Australian civil and environmental engineer who has worked in design, construction and remediation of drainage and sewer pipes in Australia, New Zealand and the UK. She has passion for all things pipes and is also one of the Co-founders of VAPAR.

Experience the future of pipe condition assessments.

Sewer inspection using CCTV

How frequently are sewer pipes inspected? 

How frequently are sewer pipes inspected?

How frequently are sewer pipes inspected?

There are over 11 billion meters (36 billion feet) of wastewater pipes that have been installed underground around the world, and this number continues to grow as the number of dwellings increases to support a growing population. A lot of these wastewater pipes have been installed in the last 40-70 years, and the pipes themselves come in a variety of materials and diameters.  

large sewer

The design life of a wastewater pipe?

Engineers design pipes for a certain design life, meaning the duration of time that the asset is expected to be in use before it deteriorates to the point of failure. In the case of underground wastewater pipes the design life is generally between 100 years and 150 years. During the pipes design life, it is prudent to check the pipes regularly to make sure that they are not blocked or broken.

Sewer inspection using CCTV

How frequently are these wastewater pipe inspections carried out?

This process is called an inspection and is usually carried out by trained professional using a small CCTV camera that is remotely driven through the pipe, capturing video footage of the internal condition of the pipe as it goes. The best practice is to undertake these inspections at a frequency of around once every 10 years, equivalent to inspecting 10% of the network every year. This frequency means that it would take the relevant water authority 10 years to get around to the same pipe if it were to continuously inspect their pipe network. Water authorities are inspecting their network continuously, but not at the ‘best practice’ frequency of once every 10 years. The frequency at which pipes are inspected differs based on the water authorities’ budgets and the risk of that asset’s failure to the community and environment. In some areas and countries, it is common for pipes to be assessed at a much lower frequency i.e. Inspected at less than 10% of the network every year. In the United States, almost 7% (source: https://www3.epa.gov/npdes/pubs/sewcl.pdf) of the network is inspected each year, but other countries like the United Kingdom and Australia (based on anecdotal industry experience) is less than 5%.  

How frequently are these wastewater pipe inspections carried out?

One way to increase the frequency of wastewater pipe inspections is to decrease the cost of the inspection itself. To decrease the cost of an inspection there must be an associated increase in productivity. This can come from new hardware, software, more effective training methods and materials, or by applying an improved process to inspections. Another way to increase the frequency of inspections is to increase the budget associated with carrying out inspections, however, this is a very challenging method since most water authorities are budget constrained and therefore have a limited ability to apply this method. 

About the Author

Amanda Siqueira is an Australian civil and environmental engineer who has worked in design, construction and remediation of drainage and sewer pipes in Australia, New Zealand and the UK. She has passion for all things pipes and is also one of the Co-founders of VAPAR.

Experience the future of pipe condition assessments.

Underground sewer

What material types are used for sewer pipes?

What material types are used for sewer pipes?

What are sewer pipes and where do they go?

Wastewater pipes are pipes that carry wastewater from a property to the source of disposal. The source of disposal may be different depending on where the property is located relative to major urban centres, but for most people the source of disposal is a bigger ‘trunk main’ pipe that eventually leads to a sewage treatment plant or ocean outfall. Because these pipes manage wastewater from every property, they are under the ground almost everywhere people live. There is an estimated 11 billion metres (36 billion feet) of wastewater pipes in the world. That’s a lot of pipe! 

Underground sewer

What are sewer pipes made of?

With so much pipe being put in the ground, what are they actually made of? Well, it depends. Depending on the use of the pipe, and the design of the installation, different materials can be considered. For example, pipes that are used for collecting wastewater from residential dwellings can be small diameter and the pipe can be made from a variety of flexible plastics. However, pipes that are large diameter trunk mains are more likely made of stronger materials such as concrete or HDPE. 

PVC pipes

What are the other different sewer pipe materials?

If you’re looking for some great information and data to answer this question, the US EPA has a useful fact sheet on the common pipe construction and materials here. There is also a data breakdown of pipe materials in sewer pipes in a previous post that we did here. From the dataset that we analysed, the most common pipe material for sewer pipes was vitrified clay, followed by concrete, then by flexible plastics. Vitrified clay was popular because it was a cost-effective solution. More recently, flexible plastics are more common in new installations, so over time we will likely see the percentage of sewers in the ground that are plastic increase. 

About the Author

Amanda Siqueira is an Australian civil and environmental engineer who has worked in design, construction and remediation of drainage and sewer pipes in Australia, New Zealand and the UK. She has passion for all things pipes and is also one of the Co-founders of VAPAR.

Experience the future of pipe condition assessments.

Trunk sewer

Trunk sewers – changes in inspection methods

Trunk sewers – changes in inspection methods

What is a trunk sewer?

A trunk sewer is usually a large diameter pipe that wastewater from smaller diameter sewer pipes connect to downstream. These carry the wastewater from upstream catchments and carry the flow downstream to a discharge point. Depending on the size of the catchment and population upstream, the trunk sewers can be quite large in diameter, most of them are large enough for people to walk through. 

Trunk sewer

Why are sewer trunk mains needed?

A trunk sewer is the most cost-effective way to transport large amounts of wastewater from upstream populations to a downstream discharge point. If we didn’t have trunk sewers we would need to take wastewater from every property all the way from the most upstream point in the network through to the discharge point, which is cost prohibitive. Due to the importance of these large pipes to urban centres, it is imperative that they are in good condition and maintained and inspected regularly.

Due to their sizer and flow capacity, trunk sewers often have a higher consequence of failure compared to the smaller upstream collection network. If a trunk sewer was to fail due to a blockage or a collapse the results can be extremely expensive to repair, damaging to the local environment, and disrupt the use and access to surrounding public and private infrastructure.
 

How are trunk sewers inspected?

Traditionally, because of large diameter nature of trunk sewers, trained and certified professionals should be used to carry out inspections, and they do these inspections by walking through the trunk sewer. These highly skilled and trained professionals not only carry out the condition inspection of the pipe, but also complete this in a safe manner. It is normal for these inspections to be carried out while the sewage is still flowing in the pipe which means the inspection should only be carried out in low flow times of the day (i.e., not during peak usage or after recent rainfall) and when the section of pipe to be inspected is well ventilated and monitored.

The airspace in the truck mains is considered to be a hazardous environment due to the H2S gas generated from raw sewage. Additionally, the pipes are ‘confined’ in nature (i.e., There is no free flow movement of air). For that reason, forced ventilation equipment is sometimes used and people inspecting the pipes wear gas masks and gas monitors for the duration of the inspection.  

What are the changes in the trunk sewer inspection technology?

There is new technology available on the market that means that people don’t need to enter these hazardous and confined environments. This new technology improves the safety outcomes for the inspection process dramatically as they can reduce or eliminate the physical entry of personnel. The devices used can be tethered or untethered, meaning that the inspection device may or may not be connected to a particular location. An example of this technology is floatable cameras that undertake 3D imaging of the pipe as they flow through. There are also vendors that provide wheeled robotic inspections, whilst others provide drone hardware that fly through the pipe. 

About the Author

Amanda Siqueira is an Australian civil and environmental engineer who has worked in design, construction and remediation of drainage and sewer pipes in Australia, New Zealand and the UK. She has passion for all things pipes and is also one of the Co-founders of VAPAR.

Experience the future of pipe condition assessments.

manhole step iron

To step or not to step – that is the question: Sewer manhole step iron debate. 

To step or not to step – that is the question: Sewer manhole step iron debate

Regardless of where you are in the world, there is likely a healthy debate on the need for manhole step irons. There are many opinions from design engineers, construction teams and maintenance teams about the usefulness of manhole step irons. 

What are manhole step irons?

Step irons are installed in manholes to facilitate access to maintenance workers and/or aid self-rescue in the case of accidental entry into the sewer network. They are usually made of metal or plastic and are installed in manholes in a vertical alignment (think of a ladder) to allow people to move from the bottom of the manhole to the top of the manhole.  

manhole iron steps

Manhole step irons

What is the debate about?

Originally, step irons were installed in manholes almost without exception. But with the ever-increasing focus on safety in the civil infrastructure industry, there are questions being posed about the need for manhole steps irons. The anti-step iron argument comes from the drive to use confined spaces equipment for entry into the sewer network, primarily a harness and tripod set up over the manhole that negates the use of step irons, in fact, they can sometimes get in the way of ease of entry/egress.

In regions that enforce confine space entry practices, entry to the sewer network is prohibited without the necessary training or equipment. So removing the need for manhole step irons has a case, especially when you consider the likelihood of associated ragging, corrosion and maintenance. To this extent, some authorities have gone to the lengths of cutting out manhole step irons form existing infrastructure. 

confined space entry manhole

 Confined space entry manhole

The argument for keeping manhole step irons can be strongest in regions where manhole step irons don’t pose a significant maintenance burden, confined spaces practice is not as enforced, and/or illegal access to the sewer network is possible. The argument of self-rescue is a common reason for continuing to install the step irons. Similar to the ladders that you see installed on the edges of non-swimming water bodies, asset owners are obliged (sometimes legally) to provide a way for people to self-rescue in the event of an accident. 

Summary

In summary, there is no set way to do things. The decision on whether to step iron or not should take into consideration a number of factors, not least of which a rigorous risk assessment to understand your options. 

Have I missed anything? Leave your comment below

Has your organisation taken a position on new manhole designs, or feel free to share your personal thoughts – I would love to hear your feedback. 

For more content like this or to suggest a topic follow VAPAR on social media. 

About the author

sewer blowback

Sewer Blowbacks –Releasing the pressure!

Sewer Blowbacks – Releasing the pressure!

What is a Sewer Blowback?

A sewer blowback is when a combination of air/water/wastewater is ejected from a household wastewater fixture, such as a basin, floor drain, gully trap, and, most commonly a toilet.

This can occur when routine or reactive maintenance is being carried out on the utility’s sewer network with high-pressure water
jetting equipment. Water jetters are used to clear roots, debris and blockages in the sewer system and ensure flow occurs uninhibited. 

Blowbacks occur due to difference in pressure in both the main sewer line and the attached house plumbing. When jetting equipment is in use, water is forced into the sewer main under high pressure, this requires the displacement of a similar volume of air. The space behind the jetter is an area of high pressure, while there can be a negative pressure zone in front of the jetter nozzle. In most cases this air is forced along the sewer main or out private property vents. However, if there is insufficient ventilation, or a blockage in a house vent, this pressure will move to take the path of least resistance. This can result in pipe odors rising through floor drains, and if there is enough positive pressure the water seal in the toilet bed can be blown with force out of the fixture. 

The inverse of a ‘blowback’ can occur where negative pressure occurs in property plumbing, and the water seal in fitting bends can be sucked out, resulting in an atmospheric opening to the sewer causing the odour from the sewer to flow through the fixture into the room that it is located. In these cases, it can be rectified by adding additional water to the water seal 

sewer blowback process

Why do sewer blowbacks occur?

There are two factors that can be attributed to a sewer blowback within the property drain itself. 

A drainage vent can become blocked or restricted over time which can increase the likelihood of a sewer blowback. 

Blockages within the sewer main can also cause water to build up on the upstream side of them; when the jetter nozzle goes past the property connection the water can be forced up the connection pressurizing the property drain unless it has somewhere to go. 

sewer blowback

How can we prevent or minimise sewer blowbacks happening?

 There are several factors that contribute to sewer blowbacks that happen during the cleaning of the sewer main, some can be minimised/mitigated, and others cannot. 

  1.  Communicating to property owners that sewer main cleaning is scheduled, and it is recommended that they keep toilet lids closed. 
  2. Opening the upstream manhole to allow additional flow into the main being cleaned. 
  3. Using lower pressure and/or flow from the jetting truck.

    Most blowbacks consist of only the contents of the water volume within the trap/water seal and is usually clean water that is replaced on a regular basis by flushing the toilet and running a tap. Some utilities will keep a blowback register of historical occurrences. It is recommended to contact them if this happens to help inform future maintenance programs and minimise the potential of it happening again.  

     

About the author Anthony Woodhouse
lateral sewer pipes

Thinking laterally – Can lateral inspections supplement your inspection program?

Thinking laterally – Can lateral inspections supplement your inspection program?

The majority of any pipe network is made up of the smaller diameter lateral connecting pipe lengths (relative to mainline lengths), so it’s no surprise that lateral inspections are becoming more and more popular.

Let’s take a look at what you need to know about lateral inspections.

lateral sewer pipes

What are lateral inspections?

Lateral inspections are inspections that survey the connecting pipe to the main line. The inspection can either be done from an access point upstream of the connection back down to the mainline or from the mainline up through the lateral connection to a connection point or boundary point upstream.

Depending on where in the world you are, these connecting pipes to the main line are sometimes called house branch connections, junctions or taps. Similarly, there are also varying ways to undertake a lateral inspection or coding defects associated with the lateral. Some countries include lateral condition coding with mainline condition coding, whilst others treat the lateral condition coding separately.

Why are lateral inspections required?

Water authorities will do lateral inspections for several reasons. Most organisations undertake lateral inspections in their network because they own the lateral and are therefore required to maintain all or part of the lateral length. There are some organisations that proactively undertake lateral inspections to investigate unknown connectivity of the network.

When should I do a lateral inspection?

Funding an inspection program can be challenging sometimes. So, adding lateral inspections to your inspection program might sound like an extra burden. Let’s look at some of the reasons water authorities choose lateral inspections for their inspection program that make the investment worth it:

  1. Investigating reported customer issues – if a customer reports an issue and no problem can be identified with the mainline pipe.
  2. Investigating network connectivity – if there are suspected illegal connections in the lateral network, or if th
  3. As a workaround for upstream access restrictions

All of the above challenges cost the water authority’s money if left unresolved, which makes the business case for lateral inspections much easier. The magnitude to which this impacts your organisation will drive a cost-benefit ratio that makes sense for your organisation’s circumstances.

lateral inspection launch

Minicam lateral launch

How can I get a lateral inspections done?

Depending on the reason for the inspection, and that site access conditions, lateral inspections are usually undertaken in one of two ways.

  1. Starting from the mainline – The first, is from the mainline using specialist inspection camera technology. This involves a type of camera that has ‘lateral launch’ functionality, which basically means a camera can be ‘launched’ up the lateral up to a length of 150 ft or 45.72 meters.  There are restrictions on the use of these types of cameras, such as lateral and camera angles. This type of inspection can help with access issues, and investigations of network connectivity.
  2. Starting from an upstream point in the lateral – The second way to do an inspection of the lateral starting from an upstream point in the lateral down towards the mainline. Its possible to do this type of inspection with a standard CCTV inspection camera (either crawler or pushrod). This type of inspection can help with investigations of customer issues.

Conclusion

The increased demand for lateral inspections can be attributed to a number of things, not least of which the availability of the technology, and increased customer reporting capability and more. Either way, these inspection methods are a great way to supplement your upcoming inspection programs where the needs arise.

About the author
pipe inclination in roman aqueducts

Pipe inclination

Pipe inclination - What goes up must come down?

What is pipe inclination?

Most of the world’s sewers and storm pipes operated as gravity pipe network. What that means is that the water in the pipes drain to the outlet point under gravity. For this to happen, the entire pipe network needs to be laid on a slight incline in the direction of the downstream outlet.

This is the most efficient method of transporting water from one point to another and has been a method used since ancient times. The Roman aqueducts brought water from the various springs in the Anio valley and its uplands to Rome, over 92000 metres or 301837.27 ft away, entirely using this method; slowly declining the aqueduct over the length of it so that water would fall in the direction of Rome.

roman aqueduct

Roman aqueducts crossing a valley

That is why when aqueducts needed to cross valleys, the Romans made every effort to keep the level of the structure constant, as dropping the level to match the valley would eventually require some sort of pumping action.

Why is inclination in pipes so important?

Pipes have inclination for the same reason as the Roman aqueducts do, water transport efficiency. The degree of inclination in pipes is a subject of much debate and is an ongoing engineering design and maintenance challenge. The more inclined the pipe, the faster the water will flow, the slighter the incline, the slower the water will flow. An interesting thing happens when water moves fast; it starts to pick up debris in the flow. Conversely, when the same flow starts to slow down, the debris that was once swept up in the flow begins to settle out.

For this reason, design engineers try to maximise inclination of the pipe network to encourage ‘self-cleaning’ velocities in the pipe network as a low-cost way to prevent blockages in the network. Anecdotally, a reasonable self-cleaning inclination would be between 1-2% grade depending on the diameter. A grade of 2.00% is the same as a ratio of 1 in 50. This means over a distance of 50 m the trench or pipe will slope down or fall 1 m from the horizontal.
However, in a flat catchment, there may not be a big enough difference in height between the top of the catchment and the bottom. When this happens, there is an increased risk of blockages and flooding because the water is not able to move itself (or debris) to the outlet as efficiently.

How can I test for inclination?

Testing for inclination can be done a couple of ways, but the most common are:

  1. Using pipe lengths and elevations between access points – Measuring the reduced level of the pipe from an upstream node and subtracting it from the reduced level of the downstream node would give you the elevation drop. Dividing that elevation drop by the length of the pipe would give you the indicative inclination of that pipe. The reason this method is only indicative is that there may be other dips and changes in direction of the pipe between the two access points that would affect the exact calculation.
  2. Using dynamic inclination measurements during CCTV inspections – Most standard CCTV camera crawler systems come with inclinometers as part of the equipment and the inclination is logged as part of the camera telemetry data. For water authorities to access this information, they will need to request and have the ability to decode this telemetry data. Or asking your CCTV contractor to display inclination on the on-screen display (OSD) as part of the inspection will also provide you with the information you need.

Conclusion

For gravity pipe networks, the inclination is very important for the efficiency of the network performance. Introducing additional debris, such as wet wipes or any other items that should not be flushed, into the sewer or storm pipe network only adds to the challenges that gravity networks have, which has the unfortunate impact of increases operational and maintenance costs for water authorities.

Effective public awareness campaigns to reduce sewer misuse such as #binthewipe and #weirdthingsinpipes can help to raise awareness about sewer misuse in the community to ensure we keep our pipes running as efficiently as possible.

About the author
Sewer vent

What are sewer vents for and how do they work?

What are sewer vents for and how do they work?

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.  

sewer vent

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