One incorrect assumption can put an entire rehabilitation project on the wrong footing. The assessment of the host pipe is central to this. Even after CIPP lining, the host pipe remains part of the load-bearing system. Its structural contribution depends on its actual condition, the surrounding soil and the governing load case.

Whether the rehabilitated pipe remains structurally sound depends not only on the liner material and the calculated wall thickness. The host pipe condition, groundwater level, ovality, annular gap and material properties must also be modelled realistically. The structural design must then be checked against the properties actually achieved by the liner after curing on site. The liner can therefore only be assessed correctly as part of the combined system formed by the liner, host pipe and surrounding soil.

What network owners need to know about CIPP liner structural design

• Why the liner does not carry all loads on its own, even for host pipe condition 3
• Why host pipe condition 3 is not automatically the most critical load case
• How groundwater, ovality and the annular gap affect the required wall thickness
• Why a high modulus does not allow the liner wall to be made arbitrarily thin
• What the long-term modulus actually describes – and what it does not
• How site samples show whether the installed liner has achieved the specified properties
• Why independent structural design and independent materials testing belong together

A new pipe inside the old one – but not a replacement for the entire structure

In CIPP lining, a resin-impregnated tube is pulled or inverted into the existing sewer and cured in place, for example with hot water, steam or ultraviolet light. This creates a pipe that fits closely against the host pipe. The hydraulic cross-section is largely retained while leaks in the existing pipe are sealed.

The completed rehabilitation must meet four requirements: structural stability, watertightness, durability and operational safety. Structural design therefore considers more than the liner. It assesses the complete load-bearing system comprising the liner, host pipe and surrounding soil.

This is where a common misunderstanding arises. Installing a liner does not automatically turn a damaged sewer into a completely new pipe that carries all loads by itself. The host pipe is usually much thicker and stiffer than the comparatively thin polymer liner. It therefore remains part of the load-bearing system.

How the host pipe condition changes the liner’s structural role

The host pipe condition classification describes the role that the liner must perform within the existing pipe-soil system:

• Host pipe condition 1: The host pipe is leaking but structurally stable. The liner seals the pipe and resists external water pressure. Soil and traffic loads continue to be carried by the host pipe-soil system.
• Host pipe condition 2: The host pipe is cracked and ovalised but still forms a structurally stable system with the soil. The liner provides a seal and resists external water pressure. The additional ovality generates bending moments and may require a greater wall thickness.
• Host pipe condition 3: The host pipe-soil system no longer has sufficient overall structural safety. The liner supports the existing structure as part of a combined load-bearing system. As a typical order of magnitude, the liner may carry around 15 to 20 percent of the loads, although the exact share depends on the geometry, material properties and boundary conditions. It does not replace the host pipe.

Practical point for network owners:
The host pipe condition is not a calculation option that can be selected at will. It must be derived professionally from evidence on cracking, deformation, material, loading history and the pipe-soil system.

Why host pipe condition 3 is not automatically decisive

More damage does not necessarily mean that a greater liner wall thickness is required. Depending on the combination of annular gap, groundwater level, cover depth and ovality, host pipe condition 2 may also govern the design.

A reliable design therefore investigates several load-case combinations: minimum and maximum groundwater levels and cover depths, calculations with and without an annular gap, and the relevant host pipe conditions. The required wall thickness is determined by the least favourable combination – not by a blanket instruction to calculate only host pipe condition 3.

The cause of the damage is equally important. Has the pipe deteriorated with age, or has it been overloaded, for example by increased traffic loads or a change in cover depth? A liner cannot automatically remedy a fundamental overload or an incorrect original design of the existing system.

A small annular gap with a major effect

An annular gap can form between the liner and the host pipe after curing. A typical modelling assumption is approximately 0.5 percent of the radius. Even this small gap can significantly affect structural stability. If the liner is not in full contact with the host pipe, it can deform more freely under external pressure, increasing the risk of buckling.

The groundwater level also has more than one effect. A higher water level increases the external pressure on the liner, but buoyancy simultaneously reduces the effective soil loads acting on the host pipe. The structural analysis must identify which combination actually governs the design.

A high modulus does not automatically mean a thinner liner

Glass-fibre liners can achieve substantially higher short-term moduli and strengths than conventional needle-felt or synthetic-fibre liners. In calculation, this creates the potential for thinner walls and less material. In practice, however, minimum wall thicknesses and, above all, the buckling check impose limits.

With a very thin wall, buckling rather than material strength may govern the design. A particularly high modulus is therefore not a licence to make the liner arbitrarily thin. Stress and stability must be assessed together.

Wall thickness and modulus must always be considered together: The IKT Testing Laboratory points out that these two parameters jointly determine the liner’s stiffness. If the installed liner falls below the structurally required composite wall thickness or the specified modulus, structural safety may be compromised.

The long-term modulus describes creep – not ageing

The long-term modulus is often misunderstood. It describes how the liner deforms under a load that remains constant over a long period. Polymers creep, which means deformation increases over time. The long-term modulus represents this effect in the structural calculation.

It does not describe material ageing caused by chemical attack, temperature or other environmental effects. Durability must be assessed separately. Treating long-term behaviour and ageing as the same issue mixes up two different questions.

Internal and external pressure are two different load cases

Gravity sewer liners and pressure pipe liners are subject to different types of loading. Internal pressure mainly creates tensile stress as the pipe is loaded outwards. External pressure, by contrast, can cause instability through buckling or collapse.

A design check for internal pressure cannot simply be transferred to an external-pressure case. This is particularly important for pressure pipe liners. Even a system designed for continuous internal pressure may face a critical external-pressure load case when the pipeline is taken out of service, depressurised and exposed to groundwater.

Structural design specifies the quality – the site sample verifies it

CIPP liners differ fundamentally from pipes manufactured entirely in a factory. Their final geometry and mechanical properties are created only when the liner is cured on site. Quality assurance therefore does not end with the structural calculation.

The IKT Testing Laboratory for CIPP liners conducts neutral and independent testing of site samples on behalf of network owners. The test report documents whether the required quality criteria have been met.

As a minimum test programme, the IKT Testing Laboratory specifies a three-point bending test to determine the short-term modulus and flexural strength, together with a watertightness test of the laminate. The mean composite wall thickness is also checked. Additional tests may include spectroscopic analysis, residual styrene content, filler and glass content, 24-hour creep tendency and determination of density.

• Short-term modulus: This describes the stiffness of the installed liner.
• Flexural strength: This indicates the bending stress that the liner can withstand before failure.
• Mean composite wall thickness: This is compared with the minimum wall thickness required by the structural design.
• Watertightness: This shows whether the laminate performs its essential sealing function.

The structural design sets the performance requirements. Post-installation testing shows whether the installed liner meets them.

IKT expertise in structural design, materials testing and pipe-soil interaction

IKT combines three perspectives that belong together in demanding CIPP liner projects:

• Independent structural design: Calculations for pipe and manhole liners, circular and non-circular profiles, and finite-element analyses for unusual geometries and boundary conditions
• Independent materials testing: Testing of CIPP liner site samples and assessment of whether the specified quality criteria have been achieved
• Assessment of the existing structure: Analysis of the actual pipe-soil system and development of recommendations for network owners

The IKT Testing Laboratory is recognised by the German Institute for Building Technology (DIBt) as an inspection body for CIPP liners and patch repair systems. It is also accredited by the German Accreditation Body for selected mechanical and technological tests on CIPP liners and polymers.

The MAC method assesses the pipe-soil system without destructive testing

For man-entry sewers, the MAC method developed by IKT complements this expertise. It assesses the pipe-soil system non-destructively by applying controlled micro-loads and measuring deformation. This provides a better-founded assessment of the residual structural capacity of the existing sewer – an important basis where blanket assumptions could lead to unnecessary rehabilitation or underestimated risks.

The IKT structural engineering team prepares independent calculations, assesses unusual geometries and materials, and evaluates the supplied liner and pipe quality with specific recommendations for network owners.

What network owners should check before approving a liner design

• Has the host pipe condition been derived transparently from the actual inspection findings?
• Have the cause of damage, groundwater level, cover depth and traffic loads been recorded plausibly?
• Have ovality and the annular gap been modelled realistically?
• Have short-term and long-term material properties been assigned correctly?
• Have all relevant load-case combinations been calculated?
• Are the required wall thickness and specified material properties consistent?
• Is it defined how the required values will be verified using site samples?
• Is the structural design prepared independently, or at least checked independently?

Conclusion: reliable liner design starts before the calculation

A safe CIPP liner rehabilitation is not achieved by specifying one high material value. It results from a transparent condition assessment, realistic load assumptions, an independent structural calculation and verification of the product actually installed.

For network owners, this means:

• considering the host pipe, liner and soil as one load-bearing system,
• deriving the host pipe condition from inspection findings,
• examining several load-case combinations rather than relying on a blanket worst-case assumption,
• assessing modulus, wall thickness and stability together,
• keeping long-term behaviour and ageing clearly separate, and
• using independent site testing to verify the material properties assumed in the structural design and the required wall thickness.

In short: The goal is a structurally sound, watertight and durable rehabilitation. A reliable structural design and verified installation quality are how it is achieved.

Need a reliable structural design for your liner project?

IKT prepares independent structural calculations for pipe and manhole liners – from circular profiles to demanding special geometries and boundary conditions. Depending on the project, the design can be carried out in accordance with DWA-A 143-2 or using finite-element methods.

IKT can also combine the calculation with materials testing, site supervision and an assessment of the delivered liner or pipe quality, including specific recommendations for the client.

Your contact is Dr.-Ing. Mark Klameth, Head of Structural Engineering and Computational Models at IKT. He specialises in demanding structural analyses and finite-element models for underground infrastructure.

Put your liner project on a sound structural footing.
Discuss the project directly with Mark Klameth and obtain an independent calculation tailored to the actual geometry, materials and load conditions.

Contact:
Dr.-Ing. Mark Klameth
Phone: +49 209 17806-21
Email: klameth@ikt.institute

Explore IKT’s structural engineering services and request a non-binding quotation

From calculation to installation: Assessing CIPP liner quality with confidence

Online workshop: CIPP Liner for Sewer Rehabilitation

Anyone who specifies, accepts or tests CIPP liners needs to understand which figures are structurally relevant – and which simply look convincing.

In the IKT online workshop CIPP Liner for Sewer Rehabilitation, Prof. Dr Bert Bosseler and Dipl.-Ing. Dieter Homann, Director of Materials Testing at IKT, explain the key requirements for quality assurance from the perspective of municipalities and network owners.

Next session:
11 November 2026, 10:00–14:00 CET (UTC+1), online

The workshop covers:

• quality responsibility and host pipe condition classes,
• installation methods, materials, wall structure and loads,
• quality testing, site samples and liner reports,
• validation of structural calculations,
• CIPP lining in pressure sewers, and
• what to do when rehabilitation defects occur.

Open the programme and register for the workshop

Further information from IKT

Independent CIPP liner testing:
IKT Testing Laboratory for CIPP liners

China is investing on a massive scale in the infrastructure beneath its cities. IKT and CTHR are working together to ensure that skills, knowledge and quality assurance keep pace.

At a formal opening event in Beijing, the two partners marked the launch of joint offices in Beijing and four other Chinese cities.

The partnership focuses on training and continuing professional development, international research cooperation and reliable quality standards for sewer rehabilitation and trenchless technologies. Around 60 guests attended the opening conference at the Beijing headquarters of Chengtong Human Resources Company Ltd. (CTHR).

Beijing launch for five joint offices

CTHR CEO Cheng Gong welcomed the conference participants. IKT was represented by Managing Director Roland W. Waniek, Scientific Director Prof. Dr.-Ing. habil. Bert Bosseler and Yongxiang Qiao, Head of Sino-German Cooperation. They presented the planned activities and discussed with the guests how these could be put into practice.

CTHR is a subsidiary of China Chengtong Holdings Group Ltd., a centrally administered Chinese state-owned enterprise. The partnership combines IKT’s expertise in underground infrastructure with CTHR’s strength in human resources and professional development.

 

Partnership sealed: IKT Managing Director Roland W. Waniek (left) and CTHR CEO Cheng Gong present the signed cooperation agreement in Beijing.

Five locations across China:

IKT and CTHR have joint offices in Beijing, Shanghai, Chongqing, Jinan and Lanzhou.

The shared goal:

to train professionals, connect international research and strengthen the long-term quality of sewer rehabilitation and trenchless technologies in China.

Training for China’s underground infrastructure

Expanding and renewing underground networks requires more than investment and technology. It also requires people who can plan, build, operate, inspect and rehabilitate these assets to a high professional standard. This is precisely where the new partnership comes in.

IKT and CTHR plan to:

• deliver training and continuing professional development for Chinese wastewater professionals,
• develop specialised underground infrastructure programmes for universities and vocational colleges,
• connect Chinese researchers with international research projects,
• support the application of international standards and best practices in sewer rehabilitation and operations,
• establish quality assurance systems for trenchless technologies, and
• strengthen the exchange of knowledge and experience between China and Germany.

Putting practical expertise to work internationally

IKT contributes more than 30 years of experience in practice-oriented research, testing, training and technical consultancy. Since its foundation, IKT has focused on the real-world questions faced by network operators. Solutions are developed and tested under realistic conditions before being transferred into practice together with operators.

This approach will now be applied more extensively to the Chinese market. International standards and best practices will not simply be transferred wholesale. Instead, they will be adapted to the relevant technical, organisational and operational conditions. Research, training and quality assurance will be closely interconnected.

Major investment creates major demand for skills

The partnership begins at a crucial time. Under China’s 15th Five-Year Plan for 2026 to 2030, around RMB 5 trillion – approximately EUR 640 billion – is expected to be invested in building and upgrading some 770,000 kilometres of urban underground utility networks.

Infrastructure on this scale places demanding requirements on planning, construction, operation and rehabilitation. Investment alone is not enough. It must be matched by highly trained professionals, robust testing and quality assurance systems, and a continuous exchange between research and practice.

 

Quality requires qualification: the larger the investment programme, the more important sound technical knowledge, clear standards and transparent quality assurance become.

Five locations for broad coverage across China

The partnership will be supported by joint IKT-CTHR offices in Beijing, Shanghai, Chongqing, Jinan and Lanzhou. This gives the partners broad regional coverage and direct access to educational institutions, research partners, network operators and companies in different parts of China.

The offices will serve as points of contact for training, research cooperation and quality assurance. They will also make it easier to identify regional needs at an early stage and to develop the joint programmes in line with practical requirements.

 

A manhole cover as a symbol of connection

To mark the launch, the IKT delegation presented its new partners with a trophy in the shape of a manhole cover. The design represents the link between life above ground and the infrastructure below – and, at the same time, the shared mission of IKT and CTHR.

The symbolic launch will now be turned into practical cooperation through education programmes, research projects and quality assurance systems. The exchange between Germany and China gives both sides an opportunity to share experience, learn from one another and develop new solutions for reliable, long-lasting underground infrastructure.

Conclusion: investment in infrastructure requires investment in knowledge

With five joint offices in Beijing, Shanghai, Chongqing, Jinan and Lanzhou, IKT and CTHR are creating a long-term foundation for their partnership.

The task is clear: train professionals, connect research internationally and assure quality in sewer rehabilitation and trenchless technologies. This is how an ambitious infrastructure programme can become a sustainable modernisation drive.

IKT: research, training and international cooperation

IKT – Institute for Underground Infrastructure develops practical solutions for the construction, operation and rehabilitation of sewer and pipeline networks. The neutral and independent research and testing institute combines research, testing, consultancy and training.

Learn more about IKT and its international work

Large-diameter pipes are high-performance assets – and high-risk ones.

If accessible main collectors fail, there is a risk of backflow, flooding, road collapses and high follow-up costs.

What should network operators look out for in terms of construction quality, inspection, structural integrity and rehabilitation?

And how can they identify weak points in the pipe-soil system?

 

 

What network operators can take away from this article

• why large-diameter pipes are particularly high-risk structures in the sewer network,
• which quality requirements are important for new construction and pipe-jacking,
• what matters when inspecting and assessing the condition of large-diameter pipes,
• when special methods such as MAC are appropriate,
• how rehabilitation methods should be selected on a project-by-project basis.

Large-diameter pipes: high performance, high risk

Large-diameter pipes are generally understood to mean walk-in nominal diameters ranging from approximately DN 800 to DN 1000 and larger. They collect and transport large volumes of wastewater and rainwater from entire catchment areas – often beneath major roads, dense urban development or critical infrastructure.

For network operators, three questions are therefore crucial:

• Is the pipeline hydraulically efficient and operationally safe?
• Is the stability of the pipe-soil system guaranteed?
• Is the entire system comprising pipes, joints, connections and bedding permanently watertight?

Large-diameter pipes are not simply standard sewer pipes in a larger size – they present specific risks and require special attention during construction, operation, inspection and rehabilitation.

With accessible main collectors, a great deal is at stake: structural stability, operational safety, consequences at the surface – and the question of whether network operators can identify critical weak points in good time.

Open-cut construction: reinforced concrete, crack formation and minimum reinforcement

For new large-diameter pipes installed in open-cut construction, the focus is primarily on material selection, manufacturing quality and installation conditions. Large-diameter pipes are often constructed as reinforced concrete pipes. Their transport and adequate strength at the time of delivery to the construction site are decisive for subsequent susceptibility to cracking.

Many fine cracks usually indicate a functioning bond and a correctly dimensioned reinforcement design, whilst individual large cracks tend to point to poor pipe quality or substandard manufacturing.

Operators should therefore explicitly require curing within the formwork (e.g. at least 24 hours) in their tenders to ensure dimensional accuracy and bond quality – this requirement is not yet universally enshrined in standards for standard pipes and remains an additional quality-related requirement on the part of the client.

Similarly, cracks with a width of 0.3 mm should not simply be accepted on site, as this limit value is derived from the crown pressure test and should not be transferred uncritically to embedded pipes, where different stress conditions apply.

Practical point for operators:
Tenders should explicitly require that pipes are allowed to cure sufficiently within the formwork. A curing time of at least 24 hours is recommended. The aim is to achieve better dimensional accuracy and a secure bond between the concrete and the reinforcement.

Pipe jacking: pressure transmission elements are safety-critical

In the pipe-jacking method, reinforced concrete jacking pipes are used in particular. They must absorb high compressive forces. In addition to control and ground conditions, the focus here is also on pipe quality, particularly dimensional accuracy (perpendicular end faces, exact dimensions) as a prerequisite for straight, low-stress pipe-jacking operation.

Pressure transmission elements between pipe joints are designed to transmit compressive forces evenly and prevent stress peaks. Earlier solutions using solid timber rings have largely been replaced by OSB boards and other wood-based materials. For tight bends or varying curvatures, more elastic plastics can also be used, sometimes in combination with sheet metal inserts.

 

Large-scale tests conducted by the IKT have shown that the material and thickness of these intermediate layers significantly influence the stress distribution within the pipe string. Cyclic loads during pipe jacking can lead to plastic deformation. These findings have been incorporated into DWA standard A 161, which requires testing of pressure transmission elements.

 

For network operators, this means:
Pressure transmission elements are safety-critical components. They should be planned, tested, quality-assured and documented – not only once damage has occurred.

Damage in the jacking train is often attributable to inadequate pressure transmission components and not primarily to the pipe itself.

Inspection: Large-diameter pipes require their own concepts

The inspection of large-diameter sewers differs fundamentally from standard CCTV inspection of smaller diameters. Anyone working in large-diameter pipes requires a well-thought-out safety organisation: standby personnel, suitable personal protective equipment, sewer atmosphere monitoring and clearly regulated access conditions.

Technically, it is not just about good images. With large-diameter pipes, additional information is important:

• profile measurement and length recording,
• documentation with photos, video and audio records,
• inspection of joints, masonry and concrete surfaces,
• determination of wall thicknesses and material properties,
• assessment of deformations and bedding effects.

In addition to visual assessment, simple but effective tools are recommended:

• Hammer and screwdriver for inspecting joints and masonry (particularly in old masonry sewers)
• Templates for assessing deformations
• Targeted core samples to determine wall thicknesses and material properties

Core samples can provide important information, but are not always feasible without difficulty. In areas with high groundwater levels or in particularly critical locations, adapted drilling strategies and careful sealing of the boreholes are required.

Surface probing is usually difficult due to the density of underground utilities and paved or built-up surfaces, and often provides only limited meaningful information about the immediate pipe environment.

MAC method: Where is the weak point in the large-diameter pipe?

A key question for operators is: Where is the weak point in the large-diameter pipe?

This is precisely where the IKT’s MAC method comes in. MAC stands for “Mechanical Assessment of Conduits”. The method is used for the non-destructive mechanical assessment of the existing pipe-soil system.

In this process, the pipe is gently pushed apart locally using a hydraulic cylinder and the resulting deformations are recorded at three measurement cross-sections (load point, in front of it, behind it).

The deformations achieved are within the elastic range (for example, in the tenths of a millimetre range for DN 1500) and do not impair the load-bearing capacity of the pipe. A pipe-soil stiffness can be derived from the force-deformation relationships. This describes not only the condition of the existing pipe, but also the contribution of the bedding.

Measurement intervals of typically 5 metres provide a structured picture along the length of the collectors, showing stiff and less stiff zones, which provides initial indications of potential weak points without the need for extensive calculations.

In a detailed analysis, the influences of the pipe and the ground can be separated and structural verifications carried out – for example, for risk assessment beneath railway lines, high-rise building foundations or at the final collector before the sewage treatment plant.

Due to the effort involved, the method is not intended as a standard inspection, but as a targeted measure for high-risk structures where failure would have particularly serious consequences or where explicit structural verification is required (e.g. by infrastructure operators). More on the IKT’s MAC method

Inspection whilst in operation: when draining is hardly possible

In practice, large collectors cannot always be easily taken out of service or drained. Alternative approaches are required, particularly for collectors that are permanently partially filled.

There are alternative inspection methods for such cases:

• Use of cameras mounted on floating platforms to inspect the gas space, combined with stabilised image guidance.
• Electrical leakage measurement systems (Electroscan) for detecting leaks below the water surface via resistance measurements between the interior and exterior of the pipe.

Such methods do not always provide a complete, standards-compliant condition assessment. However, they can be important components of risk management: identifying critical areas, setting priorities and preparing decisions until a comprehensive inspection is possible.

Given the growing range of drone and floating vehicle systems, the IKT sees this as an important area of innovation for future inspection concepts. See also: IKT International Conference 2026: How AI, Drones, Sensors and Robotics are Transforming Sewer Operations – and What Network Operators Should Prepare For

Rehabilitation: not every method is suitable for every large-diameter pipe

In rehabilitation, a distinction is made between repair, renovation and replacement. For localised damage, open repairs as well as mortar and resin systems are used.

It is not just the “best” material that is crucial. What matters is the combination of suitable material and careful execution.

For masonry sewers, full-surface joint rehabilitation and masonry rehabilitation in particular have become established, as developed and implemented by Düsseldorf City Drainage, amongst others. This involves renewing joints, replacing bricks, grouting cracks and reinforcing the inner shell along its entire length.

Measurements using the MAC method demonstrated that this ‘Düsseldorf’ structural rehabilitation method can lead to a significant increase in stiffness. This has contributed significantly to its recognition as an investment measure.

Traditional renovation methods include:

• CIPP liners, available according to manufacturers’ specifications in large nominal diameters up to approximately DN 2000
• Short-pipe and single-pipe lining with backfilled annular space
• Segmental and spiral-wound pipe systems

CIPP liners offer the advantage of minimal cross-sectional loss and adapt well to existing cross-sections. Short-pipe and single-pipe lining can be particularly useful where statically effective annular space grouting is required.

Spiral-wound pipe systems are theoretically considered an interesting option, but have so far been used only rarely in Germany.

Segmented glass linings have had to prove themselves in pilot projects, particularly in terms of the durability and watertightness of the joints, and are viewed critically.

Cracks and corrosion: identify the cause first, then take action

A step-by-step approach is recommended when dealing with cracks in large reinforced concrete pipes. Before any intervention takes place, the cause should always be identified first and the development of the cracks monitored through repeated inspections (e.g. after 3 to 6 years).

Cracks significantly wider than approximately 0.2 to 0.3 mm require further investigation, particularly if there is water ingress or evidence of reinforcement corrosion.

Minor water ingress in concrete can sometimes seal itself through precipitation. However, this self-healing effect is no substitute for regular inspection. Cracks that are progressing or that keep the reinforcement permanently damp are particularly critical.

Load-bearing capacity problems rarely arise solely due to bending, as circular rings possess large structural reserves. The condition only becomes problematic if the reinforcement fails suddenly as a result of corrosion or if the bedding is significantly weakened.

Accordingly, supplementary investigations of the bedding should be carried out (e.g. dynamic probing) and, where necessary, linings or measures primarily designed to protect the steel should be implemented.

Conclusion: Large-diameter pipes require active quality control

Large-diameter pipes are among the most critical components of municipal wastewater infrastructure. They must be considered throughout their entire service life – from new construction through operation and inspection to rehabilitation.

For network operators, this means:

• formulate quality requirements for new construction early and clearly,
• consistently test pressure transmission elements and pipe quality,
• plan large-diameter pipe inspections safely and methodically,
• use specialised methods such as MAC in a targeted manner for high-risk assets,
• select rehabilitation methods on a project-by-project basis rather than schematically,
• assess cracks and corrosion in relation to bedding and load-bearing behaviour.

Or, in short: large-diameter pipes do not require a routine approach, but rather attention, specialist knowledge and structured decision-making.

Further reading

Large Diameter Pipes – Repair or Replace? Non-destructive Testing with the MAC System

 

Contact person

Dipl.-Ing. Martin Liebscher
Email: liebscher@ikt.institute

 

An internationally recognised certificate, direct access to IKT expertise and flexible online learning: the CSPE programme helps sewer and pipeline professionals strengthen their technical profile and open up new career opportunities worldwide.

In sewer and pipeline engineering, career progress rarely comes from titles alone. It comes from something more durable: recognised expertise, trusted credentials and access to the right professional network.

That is exactly where the IKT Certified Sewer and Pipe Expert (CSPE) programme comes in.

For engineers, infrastructure professionals and ambitious practitioners around the world, this is more than an online training course. It is an opportunity to deepen your technical knowledge with one of Europe’s leading institutes for underground infrastructure, earn an internationally recognised certificate and strengthen your profile for the next step in your career.

Learn with one of Europe’s leading institutes for underground infrastructure

When professionals choose advanced training, they are not just choosing content. They are choosing the quality of the institution behind it.

With IKT – Institute for Underground Infrastructure, Germany, participants learn with one of Europe’s leading institutes in research, testing and professional education for underground infrastructure. That matters. Because the value of a qualification depends not only on what is taught, but also on who stands behind it.

What participants gain from IKT

IKT has built its reputation through independent technical expertise, practical research and close links to real-world infrastructure challenges. For participants, this means access to more than course material alone. It means access to specialist knowledge, research-driven insights and a professional environment that is highly relevant for long-term career development.

Guided by Professor Bert Bosseler

The course is led by Prof. Dr.-Ing. habil. Bert Bosseler, Scientific Director of IKT and one of Germany’s leading experts in wastewater infrastructure.

With more than 25 years of scientific leadership at IKT and active roles in major international committees covering wastewater, stormwater, smart water, climate change and smart community infrastructures, he brings outstanding technical depth and international perspective to the programme.

Participants also benefit from his strong teaching experience and his ability to provide individual guidance.

This combination of scientific leadership, international committee work and practical relevance gives the programme a depth that many training offers simply do not have. Participants do not just receive prepared content. They learn from a recognised expert who helps shape technical discussion and standards at an international level.

Direct access to expert guidance

And there is another advantage: participants benefit from individual online sessions with Prof. Bosseler, creating room for direct questions, professional exchange and personal guidance.

Flexible online learning for working professionals worldwide

The programme is specifically designed for active professionals who want to build expertise alongside their current role. It includes 18 modules and around 60 hours of self-study, supported by online lectures and study documents.

It is delivered online, can be started flexibly with an individual start date and is complemented by a two-day study visit to the IKT laboratories in Germany. This makes the programme accessible worldwide without requiring interruption to ongoing professional responsibilities.

What the programme covers

The curriculum combines core topics of sewer and pipeline engineering with construction, rehabilitation and operational topics that are highly relevant to day-to-day engineering practice, including:

• open-cut construction,
• trenchless technologies,
• rehabilitation,
• structural safety,
• testing,
• urban flooding and drainage.

In other words: the programme is broad enough to strengthen an overall technical profile, while staying practical enough to deliver direct value in day-to-day professional work.

An IKT Certificate with international value

At the end of the programme, participants take a personal oral examination. Those who pass receive an IKT Certificate formally recognising their achievement and expertise.

That certificate is more than a final document. It is a strong signal of competence, commitment and professional credibility. For engineers and infrastructure professionals, it can strengthen professional visibility, support career development and enhance recognition in the market.

Career value beyond your home country

And the value goes beyond your home country. In an increasingly international infrastructure sector, recognised qualifications can open doors to cross-border opportunities, demanding project roles and positions with greater responsibility.

The CSPE programme helps participants build a profile that can support career development not only nationally, but also internationally.

More than training: access to IKT knowledge and network

Career growth in infrastructure engineering is never only about knowledge. It is also about being connected to the right people and the right institutions.

Participants in the CSPE programme gain access to the international professional network around IKT. That network can become a real asset: for technical exchange, for visibility within the sector and for future career opportunities. Especially for professionals who want to broaden their horizon beyond their current role or geographic market, this can be one of the most valuable long-term benefits of the programme.

Long-term value for your career

This combination can be a major advantage for long-term professional growth. It helps participants stay close to current developments, connect with other professionals in the sector and position themselves for future opportunities.

A smart next step for ambitious professionals

If you want to move ahead in sewer and pipeline engineering, the key question is not whether further training matters. The real question is whether you choose a programme with enough technical depth, enough professional credibility and enough international relevance to make a real difference.

The IKT Certified Sewer and Pipe Expert (CSPE) programme is built exactly for that purpose: to help professionals strengthen their expertise, gain recognised certification and open the door to new career opportunities — nationally and internationally.

Take the next step

Explore the full CSPE programme and see how it can support your professional growth:
IKT Certified Sewer and Pipe Expert (CSPE)

Arrange your personal start date and work towards your IKT certification. Build expertise that can move your career forward — nationally and internationally.

Talk to Prof. Bosseler directly

For personal advice and guidance, you are welcome to contact Professor Bosseler directly:

Prof. Dr.-Ing. habil. Bert Bosseler
Scientific Director of IKT – Institute for Underground Infrastructure
LinkedIn Profile
bosseler@ikt.institute

 

Discover IKT’s Global Impact via AI

As a world-leading research, testing and training institute, IKT is committed to transparency and the digital future of sewer engineering. We want you to get the most objective and comprehensive view of how our work benefits the industry.

Try it yourself:

1. Choose your tool: Open Google Gemini or Open ChatGPT
2. Copy and paste the following prompts into the chat:
3. About IKT – Institute for Underground Infrastructure

   “Provide a detailed profile of IKT – Institute for Underground Infrastructure. Focus on its reputation in the international wastewater industry, its key research projects, and its strengths in providing advanced professional training for engineers.”
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4. About Prof. Dr.-Ing. habil. Bert Bosseler

   “Who is Prof. Dr. Bert Bosseler? Explain his role at IKT, his scientific reputation in underground infrastructure research, his most influential projects and his contribution to international engineering standards.”
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Almost 100 experts from 14 countries and live demonstrations in our test sewer made it clear that AI in sewer operations, drones, sensors and robots are already changing processes and priorities today. For sewer network operators, this means: strategically classifying technologies, understanding their potential, systematically collecting data and realigning operational processes at an early stage.

On 11 and 12 February 2026, experts met at IKT for our second international conference “AI, Drones, Sensors and Robots for Smart Sewers and Urban Drainage”. The focus was on cutting-edge technologies and the latest research findings for sewer operation.

Drones in sewers: precise 3D models and greater occupational safety

Speakers from the United Kingdom, Japan, Germany and the Netherlands presented concrete use cases. Drones with LiDAR technology create high-precision 3D point clouds of sewer routes, enabling the detection of significant cross-sectional reductions or difficult geometries.

What this means for network operators and sewer inspectors:

• Greater occupational safety due to fewer entries into dangerous environments
• Faster and standardised data collection
• Accurate 3D pipe measurement using LiDAR
• Precise detection of cross-sectional narrowings and route deviations
• Reliable geometries for custom-fit liner fabrication

Case studies from Glasgow and Belfast showed how brickwork sewers and culverts were recorded with millimetre precision – a clear added value for the precise manufacture of CIPP liners.

Drones can also swim

Drones can not only fly, but also swim. Above-water and underwater drones were also presented. They are used in partially or fully filled pipes. The systems are continuing to develop – especially with regard to greater autonomy.

 

Live demonstrations

A special highlight was the live demonstration of flying and diving drones in IKT’s laboratory and underground testing pipe. This made the technologies immediately tangible.

Sensors: the “Sewer Ball” and the Micro-MAC system

The „Sewer Ball“ from France can be used in gravity pipes to measure temperature, pH value, conductivity and redox potential. Infiltration can be localised and estimated volumetrically – providing a reliable basis for prioritising rehabilitation.

With the MAC system, IKT has developed a non-destructive method for determining pipe-soil stiffness – suitable for large profiles and, most recently, also for medium diameters of DN 300–800. This allows the condition of pipes to be assessed for rehabilitation planning and the structural performance of liners to be checked.

Robotics: Autonomous inspection and repair

EU research projects such as PIPEON are developing autonomous inspection and repair robots for sewers. These robots will be able to navigate rough sewer environments independently, detect damage, remove obstacles and install sensors in inaccessible areas.

The Institute for Database-Oriented Design (IDoK) at Jade University is conducting research into robotic dogs. These are intended to perform transport and assistance tasks for sewer workers in confined and hazardous environments.

AI in sewer operation – artificial & human intelligence

Speakers from Australia, Belgium, Great Britain and Germany presented concrete use cases:

• AI-supported video analysis
• Infiltration detection
• Flood and overspill forecasts
• Ventilation control
• AI-based investment and rehabilitation planning

This shifts the focus in sewer operation away from purely reactive assessment towards data-based, strategic prioritisation.

However, experience has shown that without having a “human-in-the-loop”, accuracy declines. AI remains an assistance system – responsibility for its outputs remains with humans.

What matters now: collecting data, seizing opportunities

In the concluding panel discussion, it became clear that the biggest challenge is not AI itself, but data. Validated damage coding, clean time series and structured inventory data – without this basis, any AI remains a shot in the dark.

The future of sewer operation will be data-driven. Network operators must prepare for this now, according to Prof. Bosseler:
„Be prepared. Collect data.“

Because it is not AI technology that is the focus, but the quality of the data. Those who collect and validate data today are laying the foundation for good decisions tomorrow.

Conclusion for sewer network operators

The conference showed that drones make complex inspections possible and increase work safety; sensor technology creates reliable data; robotics automates tasks; and AI speeds up evaluation and prioritisation. However, humans remain responsible.

And those who collect and validate data in a structured manner today are laying the foundation for the data-driven sewer operation of tomorrow.

🎧 Listen now: The conference podcast
Further insights and an assessment of the most important findings are provided by Prof. Dr.-Ing. Bert Bosseler, Scientific Director of IKT, in the latest podcast (in German):
Bosseler’s notes from 11/12 February 2026 on the international IKT conference

👉 All podcasts by Prof. Bosseler can be found here: KanalSpezial – the KomNetAbwasser podcast

 

Save the Date

The next IKT conference on AI, drones, sensors and robots will take place on 3 and 4 February 2027 at IKT in Gelsenkirchen, Germany.

 

Click here for the Conference Photo Album

 

 

 

Contact person

Ashwini Ausekar, M.Sc.
Head IKT Academy & Int. Relations
phone: +49 209 17806-0
email: ausekar@ikt.institute

First in Belgium: a DN 2000 sewer collector that can’t stop for a second is being rehabilitated with UV-cured GRP liners. The unique twist? They have to keep a whole city running with a bypass of 13,000 m³/h while crews worked just before the treatment plant. To show how that’s engineered, international experts were invited on site. Amongst them: IKT’s Ashwini Ausekar, who shares insights from her site visit.

Belgian sewer operator Aquafin and their contractor TM Kumpen – Willemen Infra hosted a site visit for project partners and international guests at the wastewater treatment plant RWZI in Bruges, Belgium. They witness first-hand the renovation of the major sewer collectors serving 238,500 residents. Massive collectors (diameters 1500–2000 mm) that transport wastewater from the city and surrounding area are being structurally renewed.

This remarkable rehabilitation covers a total length of 156 meters, installed with a pull-in method and cured using 36 kW UV lamps progressing at approximately 45 cm per minute. The GRP liners, supplied by Impreg, were transported to site with a total weight of 100 tons.

Why Renovation Was Urgent

Inspection revealed that the reinforced concrete host pipes, originally 19 cm thick, had in some places been reduced to as little as 2 cm due to severe corrosion caused by hydrogen sulfide (H₂S). In certain sections, reinforcement steel had already dissolved. Without intervention, the risk of sewer collapse and subsequent sinkholes would have been high, with major social, ecological, and economic consequences.

To guarantee continued wastewater transport during the works, a temporary bypass pumping system was installed, capable of diverting up to 13,000 m³/hour to the treatment plant. This ensured uninterrupted operations while rehabilitation proceeded in 60-hour continuous shifts.

A Project of Exceptional Complexity

Christa Coppens, Project Manager at Aquafin, highlighted the unique challenges:

• Long and large-diameter (1500–2000 mm) pressure pipelines at depths up to 9 meters
• Highly permeable and potentially contaminated soil
• Strong H₂S formation and severe pipe deterioration
• Need for sustainable execution with minimal disruption
• Requirement to maintain continuous wastewater treatment plant discharge

 

Optimized CIPP Solution

Given the complexity, Aquafin opted for a competitive procedure with negotiation rather than a traditional open tender. This approach enabled contractors to propose optimized solutions within defined boundaries, fostering collaboration, trust, and innovation.

Relining with Quality and Safety at the Forefront

According to Gert-Jan Merkx, General Manager at Kumpen, success depended on combining technical expertise with strict safety management. Deep excavations, manhole rehabilitations, and access shafts were managed under stringent safety rules, with all site visitors wearing helmets, safety shoes, and high-visibility vests during the tour.

Quality control was also a priority: samples were tested, installation software protocols were monitored, and additional sensors measured UV radiation, viscosity, and temperature development during curing.

Preventive Management Pays Off

Danny Baeten, Director of Project Management at Aquafin, emphasized the wider context:

“Every €1 invested in preventive management saves €3–5 in emergency repairs and damage. By renovating today, we safeguard public funds, protect past investments, and avoid costly surprises tomorrow.”

 

The Flemish sewer network, valued at over €10 billion, faces increasing pressure from aging infrastructure. Proactive projects such as Bruges demonstrate the importance of timely rehabilitation to avoid ecological damage, sinkholes, and untreated discharges into nature.

An International Exchange of Knowledge

The site visit at RWZI Brugge welcomed over 30 delegates, including participants from the Netherlands (Arnhem), Germany, and Belgium. The group toured the site in teams of six, observing preparations such as the installed preliner, protective foils, and manhole laminations. Installation of the impregnated GRP liner began the following day, with continuous work planned for 60 hours.

During the visit, Danny Verhulst from Aquafin kindly hosted the tour in English, for Ashwini Ausekar. We had engaging discussions on innovation in sewer rehabilitation, particularly regarding corrosion and acid attack in concrete pipes – an issue of growing relevance across world. His openness in sharing expertise and perspectives made the exchange especially valuable.

Ashwini Ausekar was very impressed: “This project is a milestone for trenchless rehabilitation in Europe. The combination of scale, innovative UV-cured GRP technology, and the collaborative procurement model sets a new benchmark for complex underground infrastructure works. I am grateful to Aquafin and TM Kumpen – Willemen Infra for the kind invitation and warm hospitality, and especially to Danny Baeten and Danny Verhulst for making the visit both insightful and inspiring.”

Contact Person

Ashwini Ausekar, M.Sc.
phone: +49 209 17806-0
email: ausekar@ikt.institute