pipe grade target

Targeting the Correct Pipe Slope

Targeting the Correct Pipe Slope

Why is pipe slope important?

Most wastewater networks rely on gravity to function. The term ‘💩 runs downhill’, wasn’t coined by accident. Interconnected gravity sewer pipes collect flow from customers and transport the wastewater downstream to a treatment plant through a series of gravity pipes, pump stations and pumped mains. 

When designing new gravity sewer mains, the ground topography and required grade of the sewer is the driving factor in determining where it will be constructed and how deep it will need to be. A sewer that is too steep will result in fast flow and increased turbulence. A sewer that is flat or has a sag (belly) is problematic and likely to result in ponding water and a build-up of sediments and solids. This gradual build-up of deposits can create blockages and overflows.  

Pipe sag or belly

Figure 1 – Problematic flat spots in a pipe 

Different ways to measure pipe slope and straightness?

Following the construction of a new sewer, a range of tests and checks are carried out to ensure it has been constructed as per design and is fit for purpose. These checks can include an air pressure test, hydrostatic test, ovality test, and pipe grade check. 

Utility organisations, who are the owners of the pipes, may use a variety of methods to be satisfied the new pipe has been constructed to design by housing developers or contractors. These tests check to see if the pipes are straight, free from obstruction and will achieve self-cleansing velocity. Tests can include: 

  • Ball Test 

    A smooth ball is placed at the upstream end of the sewer pipe and should run unobstructed to the downstream end. 

  • Light & Mirror Test 

    A light and mirror are sometimes used to ensure a new sewer main is straight with no unintended horizontal or vertical bends. The projection of a strong light through a straight sewer can be confirmed with a full circle of light visible at the end. 

  • Dynamic Inclination 

    Many CCTV camera crawler systems come with inclinometers that will display the grade of the pipe directly onto the inspection video. Sections of the pipe that are too flat or have a sag/belly can be identified from this displayed value. 

Digital inclination recorded by a CCTV crawler

Figure 2 – Digital inclination recorded by a CCTV crawler 

An out of the box solution!

On a recent trip to the USA, the VAPAR team discovered an out of the box solution from a pilot project in Oregon. The City of Salem have been using an alternate inclination testing approach for decades. It has worked so well for them; they continue to use this unique method to check new pipe meets their requirements. Just prior to the CCTV pipe acceptance inspection, tracing dye is released into the pipe to be tested. If the pipe has a consistent negative slope the dye will not collect and pool in a sag. If there is a pool of dye, then there is a sag present, but the dye will not be able to quantify the magnitude of sagging. 

The method employed by City of Salem is novel in its ability to identify and quantify a sag in a pipe. A target is installed in front of the CCTV camera that clearly identifies if a sag is present. The magnitude of the sag can be observed using a target where the rings correspond to their internal acceptance levels. Any significant sag in the pipe is immediately obvious as the dye level will reach the 4th target ring.  

Figure 3 – Crawler camera with dye target mounted out  front 

When the pipe doesn’t meet the required slope

If there are a number of these instances of this occurring, it may trigger a complete pipe relay. A single instance where the dye reaches the 5th target ring will generally require a dig-up to address the sag and remove the risk of settling deposits and blockages. In-service pipes with sags/ponding often require regular jetting to minimise this risk. 

Figure 4 – The City of Salem target 

Evolution of ideas

The team at the City of Salem are an excellent example of not limiting the approach to a problem or task with a narrow and set method, but rather to think about the job at hand and include innovative ideas to achieve a desired outcome. Testing alternate equipment, technology, and methodologies is an important part in process evolution throughout the world.  

We would love to hear from others who have a unique solution to complete a part of their job! 

About the Author


Mark Lee is the Business Development Manager (Aus/Nz) at VAPAR and a former Senior Asset Engineer who has spent more than a decade managing the asset lifecycle of infrastructure. He has extensive experience managing pipeline networks, including design, construction, condition assessment and decommissioning.

Mark lee posing for a photo

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.

sewer inspection software featured image

Sewer Inspection Software 

Sewer Inspection Software

Why is asset condition important?

One of the fundamental tasks of an asset manager is knowledge of asset condition. Whether this is buildings, bridges, plant, or pipes; collecting accurate information on the condition of the asset base is essential in understanding risk, developing budgets, and preparing asset maintenance and repair programs. 

 For those that manage wastewater and stormwater pipe networks, there is an additional challenge with the assets requiring inspection usually being located underground.  

What is the role of inspection software for sewer and stormwater pipes?

With cities and utilities managing vast pipe networks, there is a necessity for an efficient way to collect data and make decisions based on this information. The typical requirements of sewer inspection software are: 

  • Record defects and pipe features to inform pipe condition and details 
  • Apply consistent scoring of defects based on regional coding systems 
  • Provide a method to grade pipes to determine priority for maintenance and repair work that is required 
  • Generate informative reports to share inspection details with relevant stakeholders 
  • Deliver a structure for further data analysis, and information transfer to asset management software and geographical information systems 
VAPAR sewer inspection software

Figure 1 – Current generation of pipe inspection software

Regional differences between inspection codes

Different countries and regions around the globe have developed pipeline inspection codes in slightly different ways. The goal of each of these codes is typically the same; to provide a uniform standard for a region to apply a consistent approach to the inspection of pipes. 

Below is a list of some of the most common regions and codes that are used around the world. 

North America 

Code: Pipeline Assessment & Certification Program (PACP) Reference Manual 

Issuer: National Association of Sewer Service Companies (NASSCO) 

 United Kingdom 

Code: Manual of Sewer Condition Classification (MSCC)  

Issuer: Water Research Centre (WRc) 


Code: WSA 05 – 2020 Conduit Inspection Reporting Code of Australia 

Issuer: Water Services Association of Australia (WSAA) 

 New Zealand 

Code: New Zealand Gravity Pipe Inspection Manual 

Issuer: Water New Zealand (with ProjectMax) 

 European Union 

Code: DIN EN 13508-2 Investigation and assessment of drain and sewer systems outside buildings – Part 2: Visual inspection coding system 

Issuer: European Committee for Standardization (CEN) 


pipe inspection manual picture

Figure 2– There is a variety of regional coding standards around the world 

How recording inspections has changed over the decades

Clay sewer pipes were first constructed by the Mesopotamians over 6,000 years ago, with modern city sewer construction beginning in the 19th century. Before inspection crawler cameras and computers, these underground pipe networks still required periodic inspection. This was initially a visual inspection that was carried out either by walking or floating through the underground infrastructure. 

Old sewer inspection by canoe

Figure 3 – Pipe inspection by canoe (1908) 

Inspections gradually moved to photography and hand-written logs of defects. The 1950s saw the first development of remote camera deployment into underground pipes. As videography become an option in the 1970s/80s, the opportunity to capture condition information in a video format became accessible to utilities.  

Sewer inspection software evolved as computers became commonplace in businesses. Software provided numerous advantages over written/typed records. Errors reduced, consistency improved and access to information became easier. 

VHS capture of pipe inspection


Figure 4 – VHS capture of pipe condition information 

Video capture then evolved from VHS to digital media storage, and as data capture and storage advanced, inspection file size also grew. This presented fresh challenges for organisations as the transfer and storage of substantial amounts of data required careful management to ensure the condition information remained accessible to those who needed access to it.  

The current generation of sewer inspection software is using artificial intelligence to automatically identify defects and automate many of the tasks that are logic based and ideal for computer-assisted decisions. Data storage is increasingly moving into the cloud to provide fast and organised access to the growing amounts of collected data with ease. 

Pipe inspections still require operator controlled (or staged) capture of data in the field, and results processed through artificial intelligence models are combined with human quality assurance. There is excitement in the industry as the next generation of software is being advanced to further improve the tools available to asset managers.  

Watch this space!  

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.

Pipe jetting process

What is Pipe Jetting?

What is 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. 




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.