How to keep roots away from sewage pipes? IKT investigates protection systems in a long-term project. Researchers want to find out which protective measures are suitable. They have now dug up their worldwide unique in-situ test rig. The initial results are surprising.

At the start of the project, IKT laid wastewater pipes with various protection systems underground. They then planted trees on top.

The researchers left the roots to grow in peace for six years. They only checked on them from time to time. In August 2024, the time had come: they dug everything up to see how the roots had developed and how well the pipes were protected from them.

 

Roots obstruct drains
Sewage network operators are constantly struggling with root ingrowth in sewage pipes. Obstacles to drainage can form and even cause complete blockages. These then have to be laboriously milled out. In the worst case, the only solution is expensive excavation. Structural protection measures are designed to prevent precisely this, so that trees and pipes can coexist in harmony in cramped urban spaces.

Material mix in the experimental setup
IKT researchers therefore want to find out which passive measures are suitable for protecting pipes. Six years ago, they set up a worldwide unique in-situ test stand for this purpose. At a depth of 1.20 metres, they laid two 30-metre-long DN 150 and DN 300 sewer pipes in parallel. On top they planted five fast-growing poplars, each five metres apart.

To see how roots interact with different pipe systems, they chose pipes made of concrete, PVC, PP and GRP. The total of 15 pipe connections are standard push-in joints, shrink sleeves, transition sleeves and an experimental bentonite tape.

What works against root ingrowth?
In the bedding area around the trees, the IKT researchers installed eight root barriers, such as foils and vertical panels from various manufacturers, as well as two mineral encapsulations.

That was six years ago. The poplars are now ten metres tall and in great shape. Time to see how the roots have grown and whether the protective measures are working.

Digging like archaeologists
The IKT researchers took archaeological care when excavating the roots of their trees so as not to damage the roots.

They meticulously documented how the roots had grown. Their painstaking work took a whole week with the help of hand shovels, suction excavators and compressed air lances.

Roots surprise researchers
Visually alone, there was something unexpected: even thick roots branched out like an ancient Roman trident when they encountered resistance. They followed the relatively loose soil space around the sewage pipes. They looked for their way and found it. They bypassed the built-in obstacles – successfully at first glance.

Some roots penetrated deeper into the earth along the vertical protective plates, only to grow upwards again behind the obstacle. Others bypassed the protection systems sideways. All of them grew towards the bedding zone of the pipes, probably because the soil is less compacted there and they can advance more easily than in the natural soil space.

Of the 15 pipe connections, 13 withstood the roots, two did not. The connections between the vertical protective plates were also not impenetrable in all cases. The roots snaked through here too.

Back to the lab
Now it’s back to the lab, where the researchers will investigate exactly what the roots have done. The final results of this research project are expected in early 2025 – we will report back.

Thanks to the Netherlands
The IKT root test stand is located in a new development area in the city of Almere, near Amsterdam. It was set up in the winter of 2018/2019 and has now been dismantled.

We would like to thank the city of Almere and the Dutch foundation RIONED for funding the project to the tune of 205,000 euros. Prof Dr Thomas Stützel, Director Emeritus of the Biological Garden at Ruhr University Bochum, supported us with his impressive wealth of knowledge as a biologist and root expert.

 

Photo gallery: Excavation of the IKT tree root test field
in Almere/Netherlands

Click on pictures for full view

 

We warmly welcome Renotec NV as a new member of our IKT Association of Industry and Services!

Renotec NV is Belgium’s largest sewer rehabilitation company. It has more than 30 years of experience and employs 900 people.

Renotec’s range of services includes the rehabilitation of gravity and pressurised mains using:

• CIPP lining
• Pipe bursting
• Short lining
• GRP lining
• Horizontal drilling
• Slip lining
• Spray mortar and grouting
• Quick-Lock
• Laterals renovation
• Manhole renovation

More about Renotec’s activities here: Renotec NV

Renotec NV is the first Belgian member of the non-profit IKT Association of Industry and Services.

The association pools the extensive expertise of manufacturers, rehabilitation companies and engineering consultancies in the wastewater sector and contributes it to the work of the IKT – Institute for Underground Infrastructure.

The IKT Association of Industry and Services is also a shareholder of IKT. It holds one third of the shares and is represented by two members on the Supervisory Board.

The second shareholder of the IKT is the IKT Association of Network Operators, which holds two thirds of the IKT shares. Around 160 municipal urban drainage operators belong to this organisation.

You can see which other companies are members of the IKT Association of Industry and Services here: Member companies

Read about the activities and history of the IKT here
“30 Years of Sewerage Research at IKT – Institute for Underground Infrastructure: What was, what is and what is yet to come”:

30 Years of Sewerage Research at IKT – Institute for Underground Infrastructure: What was, what is and what is yet to come

When a group of far-sighted experts founded a new research institute for sewerage technology in 1994, they could hardly have imagined how important the topic would become over the next three decades. Prof. Dietrich Stein from Ruhr University Bochum, Dr. Rolf Bielecki, Senior Construction Director from the Hamburg Building Authority, and Jürgen Wilms from Hochtief AG had recognised something that is undisputed today: Germany’s, and the World‘s sewerage infrastructure needs to be renovated at great expense to address its ageing assets and now also adapted to provide resilience to climate change.

Initial investigations using camera inspection technology, which was still quite new at the time, showed that the structural condition of urban wastewater pipes was very problematic in many places. Pipes were leaking, they were hydraulically restricted and their structural fabric was under attack. The necessary funding for this was estimated to be in the high billions.

Large-scale testing at a real, 1:1 scale

The idea of IKT’s founding fathers was to explore and support this high need for rehabilitation with practically orientated solutions research and material testing. Systems and technologies for underground construction were to be researched and tested on a 1:1 scale in an institute specially created for sewerage technology.

They designed a large-scale test rig for this purpose, the likes of which had never been seen anywhere in the world before. It was to be used to simulate construction sites on a 1:1 scale, with everything that goes with it: soil structure, groundwater, soil pressures and traffic loads. Everything that exists on sewer construction sites was to be realistically constructed. The facility should enable open and trenchless construction methods, including the latest tunnelling and rehabilitation techniques.

Financial support from Ministry of the Environment

The concept met with great approval from municipal sewer network operators as well as construction companies and product manufacturers. The founders turned to the North Rhine-Westphalian Ministry of the Environment for the necessary funding.

The ministry recognised the potential of such an institute, particularly for groundwater protection, because leaking and blocked wastewater pipes endanger the environment. The Ministry therefore provided a large proportion of the funding for the construction of the institute.

Foundation in Gelsenkirchen

The institute was founded as a non-profit limited company based in Gelsenkirchen. The initial shareholders were a development association and the city of Gelsenkirchen. After a planning and construction phase of just two years, which is very short by today’s standards, IKT began operations thirty years ago, in autumn 1994.

The management team consisted of Prof Dr Dietrich Stein as Scientific Director and Felix Weddige as Commercial Director. They were supported by Dr Christian Falk as Scientific Manager. The Supervisory Board and a Friends’ Association were first headed by Dipl.-Ing. Jürgen Wilms and shortly afterwards by Dr.-Ing. Rolf Bielecki. From a handful of employees at the beginning, the IKT has now grown to 50 employees.

State-of-the-art testing technology

A large research hall was built for the extensive testing technology. The large test stand alone has impressive dimensions: made of steel, 18 metres long, six metres wide and six metres high, it is still the experimental heart of IKT today.

There is also an elastomer and an electronics laboratory as well as two gantries with large pressure cylinders for dynamic and static load tests with which earth and traffic loads of up to 4000 kN can be simulated.

First successes

In its first five years, IKT initially focussed on research into geophysical subsoil exploration, pipe jacking, sewer gasses, infiltration and tree root ingrowth. The Institute also took up the topics of pipe and manhole rehabilitation at an early stage.

One ground-breaking project was the first to scrutinise sewers that had been rehabilitated with pipe liners. Sections of pipe that had previously rehabilitated with Cured In Place Pipe (CIPP) 5 to 15 years earlier were excavated from the networks of several municipalities and thoroughly analysed.

The results revealed the entire spectrum of the installation quality issues with pipe lining. They attracted a great deal of attention from experts and laid the foundation for subsequent work focus on the quality of sewer rehabilitation, which IKT continues to pursue intensively in numerous projects to this day.

New management

As successful as the scientific research was, the business side of the initial phase was difficult.

With the economist Roland W. Waniek appointed as Managing Director (1999) and the civil engineer Prof. Bert Bosseler appointed as Scientific Director (2000), a new management team took over responsibility. Together, they and the entire team worked together to devised a new strategy.

New strategy

The core idea behind this reorganisation of the Institute was and still is to move away from purely academic research towards addressing the practical questions and issues faced by municipal network operators. This is because they are locally responsible for the construction, operation and renovation of underground networks. They decide which technologies they use, which investments they make and how they operate their networks. Therefore their needs made them the target client group for IKT activities.

Since the early 2000‘s, the Institute has consistently focussed its activities on the knowledge needs of network operators. The new mission statement has become that of creating and supporting the “informed network operator”, for whom the IKT provides scientifically sound and practically achievable project results. To this end, the Institute first and foremost addresses topics that are identified as important by network operators.

In addition, the Institute was renamed IKT – Institute for Underground Infrastructure to signal that it not only deals with sewerage systems, but also with other pipeline networks.

New shareholder structure

The new strategy also required a new shareholder structure. The city of Gelsenkirchen left as a main shareholder and was replaced by the newly founded IKT-Förderverein der Netzbetreiber e.V., to which more than 150 municipal drainage companies now belong. Any public sewer network operator can become a member. The association holds two thirds of the shares and therefore has a majority stake in the non-profit organisation.

Its function is to gather the voices of the municipalities, i.e. the demand side of our industry, on a broad basis and to help determine the project topics of the IKT. This is achieved through regular formal and informal discussions between the members of the association and the Institute.

However, because it is not only the demand side of the professional world that is important, but also the supply side with its expertise, the second IKT shareholder is the IKT-Förderverein der Wirtschaft e.V. (IKT Industry Association). More than 60 companies from the private sector belong to this organisation: manufacturers, engineering offices, rehabilitation and construction companies, primarily from Germany, but now also from countries such as Belgium, China, Japan, the Netherlands and Switzerland.

That association holds a third of the IKT shares and its function is to gather issues relating to the supply side of the industry and incorporate them into the Institute’s work. Any interested company can become a member.

New business areas

The traditional field of research was initially expanded at the beginning of the century to include three new business areas: comparative product testing, material testing and consulting. Later, training, flow measurement and managing the municipal network of wastewater companies – KomNetABWASSER – were added.

Comparative product tests

The product test projects in particular have cemented the IKT’s reputation as a neutral and independent institute. This is particularly important for supporting investment decisions by local authorities. With its comparative product tests, the Institute analyses the strengths and weaknesses of marketable products and processes. More than a dozen major product test projects have been completed to date, including on house connection repairs, manhole renovation, flow restrictors, liquid soil trench backfill and the renovation of pressurised wastewater pipes. Download here: All IKT product test reports

Municipal steering committees

A local steering committee is formed for each product test project, which determines which products are tested, what the test programme looks like and what criteria are used for evaluation. The IKT large-scale test rig is usually used for the test set-up.

This enables IKT scientists to simulate sewer situations and construction sites on a 1:1 scale. Sewer pipes, manholes and special structures are installed and damage scenarios are realistically applied, before rehabilitation is undertaken by manufacturers and contractors using their respective products and processes.

 

Supporting investment decisions

In the test rig, long-term operational loading is simulated, such as traffic loads, high-pressure cleaning and changes in groundwater pressure. IKT scientists examine the remediation results and report to the municipal steering committee. The steering committee then evaluates and grades the products. The results are widely publicised so that all municipalities can use them to support their investment decisions.

Testing laboratory for building products

IKT operates two testing laboratories for material and construction product testing. Both are recognised by the German Institute for Building Technology (DIBt).

On the one hand, there is a focus on testing CIPP liner samples that are taken at installation sites and checked for watertightness and material characteristics. The test results show clients whether they have actually received the promised installed quality. All test results are published in tabular summaries in the annual IKT Liner Report.

On the other hand, tests are carried out on treatment plants for wastewater, such as decentralised rainwater treatment plants or oil separators. In this way, manufacturers, customers and operators find out whether products fulfil the requirements and learn about the efficiency of the treatment.

 

The laboratory also offers manufacturers tests for DIBt approvals and individual product-specific testing. Everything that is used in underground construction is tested. Successful products can be awarded the coveted “IKT-Geprüft (approved)” test seal.

Here you can see how IKT operates its scheme of seals from product tests and test projects.

Due to increased heavy rainfall and because rainwater is to be infiltrated and stored, the testing centre has already extended its accreditation to infiltration products. All DIBt approval tests required for this can now be carried out at the IKT.

 

Ongoing training for practitioners

Part of the strategic reorientation is to pass on the knowledge acquired in research and product testing to the entire industry. To this end, IKT offers a varied programme of more than 120 seminars, workshops, courses, in-house training sessions and congresses.

The topics are closely coordinated with municipal network operators and cover what is important to them. This includes classic technical content on construction, renovation and operation. But the programme also includes courses on heavy rain consultancy, sewer management and regulation. Even “exotic” topics such as rat control are included. Those who pass the courses are rewarded with an IKT certificate.

Municipal network of wastewater companies

The IKT’s focus on the issues and problems of sewer network operators is particularly reflected in the municipal network of wastewater companies – KomNetABWASSER. The Institute launched this network in 2008, initially focussing on the topic of citizen advice for private property drainage.

In the meantime, the range of topics has expanded considerably. It encompasses all technical and operational issues relating to urban drainage. Over the years, a strong community of wastewater companies has developed, providing mutual support and encouragement. They exchange ideas with their peers from other municipalities, ask questions and get useful answers to sopport their own work. More than 170 municipalities across Germany are now members of KomNetABWASSER.

The network attaches great importance to continuous further training. All employees of participating municipalities can attend all IKT seminars free of charge. They also receive technical advice and materials to support their public relations work.

International orientation

IKT is very aware that the issues faced by network owners are very similar around the world, that there are lessons to learn from each other and that its research has applications internationally. So, IKT is becoming increasingly internationalised in terms of its staff, its clients, its outreach and translation of its reseach reports. Starting in 2013, the Institute has been operating a pipe liner laboratory for the Benelux region in the city of Arnhem in the Netherlands. Training courses and research are also offered there.

IKT has an office near Oxford for the UK. British network operators are advised there primarily on issues relating to sewer rehabilitation. The Institute’s overseas activities are also coordinated from there. These include international research projects and seminars.

European Laboratory Network

IKT has been part of a large European laboratory network for four years. Under the name “Consortium of Drainage Laboratories (CoUDLabs)”, renowned water researchers from seven countries have joined forces to address future issues of climate-resilient urban drainage. This network is funded by the European Union.

New investments in testing laboratory and heavy rain research

Shortly before its 30th anniversary, the IKT has extensively expanded its test laboratories. Investments have been made in state-of-the-art test rigs and equipment that significantly expand the range of services.

This means that a wider range of construction products can now be subjected to dynamic and temperature loads. State-of-the-art and novel materials can be tested for behaviour, durability and operational stability. With UV test and weathering systems, it is now also possible to analyse plastic products for above-ground infrastructure.

For the increasingly important topic of heavy rainfall and urban flooding, the construction of a test facility is being planned to simulate heavy rainfall events on a 1:1 scale. This will enable IKT to analyse and test protective measures against excessive water in the city.

These new and expansion investments totalling millions are financially supported by the EU, the state of North Rhine-Westphalia, Emschergenossenschaft/Lippeverband, GELSENWASSER and Abwassergesellschaft Gelsenkirchen.

Urban drainage agenda 2035

This makes it clear that even after 30 years of sewerage research, there will still be more than enough to do. IKT and its partners will certainly not be bored. The next ten years will be particularly challenging for urban drainage systems.

To mark its 30th anniversary, the IKT is therefore organising two conferences, one for its German clients and collaborators and one in English for its international collaborators and clients. The focus of both conferences is on the issues facing urban drainage systems and what the future will be like.

The German “Agenda Urban Drainage 2035” congress (10th/11th September 2024) will be focusing on what German urban drainage systems will increasingly be facing in the next ten years: sewer renovation, climate adaptation, AI and capacity bottlenecks.

The International Conference (11th/12th September 2024) will be hearing about the issues affecting sewerage and urban drainage in different countries and some of the solutions being adopted and reserched.

Attendees from both Conferences have the opportunity to come together and celebrate IKTs 30 years at an evening birthday party on 10th September – be there too!

IKT Congress “Agenda Urban Drainage 2035”
10 – 11 September 2024
Programme and registration here: Congress with anniversary celebration

IKT 30 International Conference
11 – 12 September 2024
Contact: naismith@ikt.institute

IKT’s Managing Director, Roland W. Waniek, and Scientific Director, Prof. Dr. Bert Bosseler, have attended the “China-Europe Conference on Pipelines and Trenchless Technology” at the end of March 2024, where they presented the latest IKT research results on the subject of pipe liner quality.

The event was organised by Prof. Dr. Jingguo Cao from the Tianjin University of Science and Technology.

 

 

The event brought together more than 700 experts in the metropolis of Jinan, the capital of Shandong province on the south bank of the Yellow River.

Prof Bosseler spoke about “Quality Assessment of CIPP Lining in Sewers” and Roland W. Waniek spoke about “International Trenchless Development Trends”.

 

Bert Bosseler presented the latest IKT research results on the quality assurance of CIPP liners, whilst Roland Waniek highlighted the advantages of trenchless construction and renovation in densely populated regions against the backdrop of economic and climate-related challenges.

The two had further interesting discussions at the Tianjin North China Geological Exploration Bureau, at the Tianjin Municipal Drainage Department and at the China International Petroleum & Petrochemical Technology and Equipment Exhibition in Beijing.

The programme also included a visit to a CIPP liner construction site in Jinan and a tour of a CIPP liner and Spiral Wound Lining manufacturer in Gongjiatun.

And at the end there was also a short detour to the Great Wall of China to the north of Beijing – very impressive!

The Chinese hosts will be making a return visit to the IKT with a delegation in May 2024 to discuss further cooperation on the topic of sewer rehabilitation. Before that, they will visit the IFAT exhibition in Munich.

 

You can find a detailed report from our Chinese hosts about this trip here:

 

Chinese report on the IKT visit to China

 

 

More information about quality assurance for CIPP liners:
Neutral and independent: IKT test centre for CIPP liners

 

CIPP liner quality: What is the essence of two decades of IKT’s research?

Prof. Dr. Bert Bosseler, our Scientific Director, and colleagues identify the key factors that are crucial for the quality of the world’s most popular rehabilitation process for sewer pipes, Cured-in-Place-Pipes (CIPP).

In a peer-reviewed journal paper we have summarized all our findings. It is a comprehensive compilation of many research projects and many thousands of CIPP tests over the years.

We also highlight the challenges that remain and the key research issues that still need to be resolved.

 

Download paper

Read now our findings in this peer-reviewed paper, free for download:

Quality assessment of CIPP lining in sewers:
Crucial knowledge acquired by IKT and research gaps identified in Germany

Authors:
Bert Bosseler, Dieter Homann, Thomas Brüggemann, Iain Naismith, Matteo Rubinato

published in “Tunnelling and Underground Space Technology”
by Elsevier
January 2024

CIPP Test Center

Find out more on how we test CIPP liner in our test center: IKT’s Test Center for CIPP Liner

Contacts

Prof. Dr.-Ing. Bert Bosseler
Scientific Director, IKT
T: +49 209 178060
E-mail: bosseler@ikt.institute

Iain Naismith, Ph.D.
Senior Research Fellow, IKT
T: +44 1491 712707
M: +44 7983 605219
E-mail: naismith@ikt.institute

 

Aging pressure sewer pipes, just like gravity sewers, require renovation. But which methods are best suited for the job? What are the pros and cons of each? The latest IKT comparative product test on pressure sewer liners offers valuable insights.

Pressure sewers are critical and sensitive elements of urban wastewater infrastructure. Many are ageing so sewer network owners are increasingly having to deal with their rehabilitation and there are different methods available on the market for this.

Consequently, the neutral, independent and not for profit IKT Institute for Underground Infrastructure, in Germany, has been examining rehabilitation solutions in an extensive comparative product test. Over a three-year period an evaluation project was undertaken on behalf of six municipal network operators from Bottrop, Bremen, Burscheid, Iserlohn, Cologne and Voerde and two regional water associations, the Emschergenossenschaft and the Wupperverband.

The project was supported by the district government of Münster and the State Office for Nature, Environment and Consumer Protection of North Rhine-Westphalia (LANUV). It was financed jointly by the NRW Ministry of the Environment and the eight network operators.

These organisations formed a steering group that determined the pressure sewer damage scenarios to be remedied, the testing programme and the evaluation of the results. IKT developed the test concept, set up the test rigs in its large 1:1 scale test pit and carried out the testing.

Six liners in the comparative product test

The steering committee selected the following lining technologies for the comparative product test:

Close-fit linier method:

• Compact Pipe (Wavin GmbH)
• egeLiner (egeplast international GmbH)

Cured in Place Pipe (CIPP) liner process:

• Esders HPS Liner (Esders Pipeline Service GmbH)
• Nordiflow WPE (NordiTube Technologies SE)
• SaniPipe (AMEX Sanivar AG)
• Starliner Structure-S (Karl Weiss Technologies GmbH)

Remediation task

For each liner system, the test setup consisted of a DN200 steel pipe with damage patterns such as holes, leaky connections, point loads, transverse and longitudinal cracks, ovalisation and incrustations. This realistically depicted the damage that network operators find in their pipes.

Class A liner systems

The central issue was whether the liners are suitable as Class A products. A Class A liner must be able to withstand internal and external stresses on its own, regardless of the condition of the host pipe. The stress testing programme conducted as part of the IKT comparative product test went well beyond the regular warranty period of five years in order to consider the entire useful life.

Test program and evaluation scheme

The test programme consists of three phases: The first phase depicted the regular, normal operation of a rehabilitated pressure pipe. Internal water pressures of between 2 and 6 bar were applied at different flow speeds.

In the second phase, the degeneration of the host pipe was simulated over a prolonged period of time. For this purpose, some of the damage scenarios in the host old pipe were worsened in order to simulate progressive damage development and the resulting changes in external influences on the liner. Test pressures and flow rates remained the same as in the first phase.

Finally, the third phase served to simulate additional, non-every day and extraordinary loads on the liner that may occur over the course of its useful life. These included high-pressure cleaning at 80 bar, abrasive substances, the rapid switching on and off of the pump or elevated groundwater levels, such as those that occur when pipes pass under rivers.

Evaluation criteria

The overall grades for the liner systems are made up of the four main criteria of tightness, stability, operational safety and quality assurance. These are divided into nine sub-criteria. The range of grades lies between VERY GOOD (1.0) and INADEQUATE (6.0).

Watertightness criterion (weighting 45%)

The main weak points found in the four CIPP liner processes were the end connections to the host pipe, there were leaks. In contrast, the PE flange and electrofusion sleeve connections of the close-fit liners were reliably watertight.

The close-fit systems Compact Pipe and egeLiner proved to be watertight after renovation. In contrast, the picture for the CIPP liner end connections was very different: Nordiflow and SaniPipe each had to be reworked once to make them all watertight, whilst the Starline end connections had to be reworked twice in order to get them tight. The Esders HPS liner remained leaky even after the connections had been repaired twice and thus it failed on this criterion.

Stability criterion (weighting 25%)

 

The stability (load-bearing capacity of the structure) was classified by the steering committee as a central “KO” (failure) criterion. It was gratifying that five of the six liner systems tested passed this criterion with GOOD or SATISFACTORY grades. They show no or only minor abnormalities such as local wrinkling.

The SaniPipe liner failed this criterion as it collapsed under external pressure. The reason for this was insufficient fabrication of the liner, which took place without static proof. It was therefore not a Class A liner and consequently received the overall rating INADEQUATE, regardless of performance against all other criteria.

Operational performance criterion (weighting 15%)

This examined to what extent the liners can withstand normal operating conditions such as pressure fluctuations, abrasion, static pressures and high-pressure cleaning.

 

Here, Compact Pipe and egeLiner scored a GOOD grade. Also, they did not form folds and obstacles along their length. However, their installation leads to a hydraulic loss of 6% compared to unlined pipe this was in the middle range. The Nordiflow and Starline liners both had folds larger than 6 mm in the installed liners sheets and thus achieved a SATISFACTORY score. However, the hydraulic power loss of the Nordiflow was particularly high at 8%, whilst the Starline was the lowest at 3%.

With high-pressure cleaning, the Compact Pipe and egeLiner close-fit products achieved a VERY GOOD rating. Nordiflow and Starline withstood this operational stress SATISFACTORILY. On the other hand, Esders and SaniPipe failed this criterion because holes and delaminations occurred. Chemical loads did not have a negative effect on any liner system.

Quality assurance criterion (weighting 15%)

Although all the manufacturers provided an installation procedure manual, some of them have significant deficits in training, test certificates and external and internal monitoring. In addition, the installed Esders and SaniPipe liners each had a continuous longitudinal fold along the length and SaniPipe had design defects, which led to a devaluation of the grade.

Overall result and conclusion

The IKT comparative product test “Renovation process for sewage pressure pipes – Class A liner” confirmed that it is possible to achieve good renovation results. However, there are major differences in the performance of the six rehabilitation technologies examined, which are reflected in the test results awarded. One of the six liners could not qualify as a Class A liner.

Passed:

• Compact Pipe (Wavin) GOOD (1.8)
• egeLiner (egeplast international) GOOD (1.8)
• Nordiflow W PE (NordiTube Technologies) SATISFACTORY (2.6)
• Starline Structure-S (Karl Weiss Technologies) SATISFACTORY (2.6)

Failed:

• Esders HPS Liner (Esders Pipeline Service) DEFICIENT (5.3)
• SaniPipe (Amex Sanivar) INADEQUATE (6.0)

Results at a glance and complete report (English)

The further deterioration of the condition of the host pipe over time was found to have no effect on the success of the rehabilitation. This applied in particular to signs of corrosion such as simulated pitting and point loads. Only in one case did the complete loss of the supporting host pipe lead to liner failure under external water pressure.

All six of the liner systems could be installed through the four 15° bends included in the rig. Three of the liners were even able to install through a further 30° bend.

The systems were able to withstand normal operating conditions such as pressure fluctuations, abrasion and static pressure without any problems. However, there are clear limits to high-pressure cleaning and holes and delamination can occur here. Chemical stresses did not affect the tightness of the liner.

All liner systems lead to hydraulic performance losses in the pressure sewer the highest up to 8% at the top. The internal diameter was reduced by more than 20% in some places in some liners. Wrinkles >6 mm could be seen on all the CIPP liners. In contrast, the close-fit liners showed no creasing whatsoever, but there was clear ovalisation in the bends.