Tuesday, May 21, 2024

Pressure pipe rehabilitation

Is there a right or wrong? Tom Sangster, Managing Director of Downley Consultants, discusses CIPP for pressure pipes covering water, gas and pressure sewers.

UKSTT recently held a very informative and interesting Masterclass on CIPP for Pressure Pipes. The Masterclass covered water, gas, and pressure sewers, considering their needs, differences, and the common ground. Both the problems and the solutions were presented and discussed, and the number of people attending was testament to the importance of the topic in the UK. Two of the keynote papers on water mains and pressure sewer rehabilitation highlighted very different approaches to solving the problems that are so widespread in these networks – one of revolution and one of evolution.

Revolution in the UK

This focused on the OFWAT funded Designer Liner project. Here the project team has been given a utopian wish-list of capabilities in order to develop a new solution for water mains rehabilitation.

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At first sight, the requirement for something that is cost effective, DWI Regulation 31 compliant, environmentally friendly, minimally disruptive and which offers long-term durability seems reasonable. But the list doesn’t end there, and we must add a lifespan of more than 100 years, self healing materials, embedded fibre, smart networks, sensors, and biofilm suppression. So, can a project with so many objectives succeed? And what does success look like? Typically, such wish-list driven projects are saddled with an all or nothing approach; achieving 80% or even 90% of the wish-list is not enough, only 100% will do – the best is often the enemy of the good so some potentially worthwhile innovations will be lost.

There are many technologies already available that can meet the primary objectives and are widely and successfully used internationally. But apparently these are not suitable for the UK needs. The reasons for this are not immediately clear. So, a smart, talented, and dedicated project team is faced with a Sisyphean task. Regulation 31 will remain a ubiquitous obstacle for future solutions as it is for current ones and while we wait for perfection to be achieved water mains will continue to fail and leaks will remain a daily occurrence.

Evolution in Germany

The Institute for Underground Infrastructure (IKT) in Gelsenkirchen has undertaken a test programme to evaluate the capabilities and limitations of Class A (ISO 11295) fully structural pressure sewer rehabilitation solutions. Supported by the Nordrhein-Westfalen sewer network owners and the State Environment Ministry a test bed was set up to test six products currently available and to compare them. The sewer owners and Environment Ministry decided the evaluation criteria and the test bed contained the full range of defects and damage scenarios that they considered relevant.

Four pressure CIPP liners and two PE close-fit liners were tested. Their performance was analysed and the sewer owners now have good information and an understanding of the capabilities and limitations of each, including several key lessons. As a result, they can implement those that performed well and do so with realistic expectations. Moreover, the limitations and shortcomings are understood so the manufacturers can address them and the technologies will evolve to meet the customers’ needs, even as they become more demanding.

Is there a right or wrong?

The contrasts between the two approaches are striking. One can argue that it is not a fair comparison because the requirements of the water and pressure sewer sectors are not the same. This however is a weak argument as fundamentally the requirements are very similar. Suitability for use with potable water is the key differentiating aspect of the water sector; the chemical conditions and frequent on off pumping cycles define the pressure sewer sector. Otherwise, the requirements to be cost-effective, durable, environmentally friendly and to involve minimal disruption are the same, as are the performance requirements: to be fully structural, leak tight and capable of lining around bends in the pipe. Which is better, or right? Each has its merits. The revolutionary approach, looking for innovative new solutions, can yield worthwhile and valuable progress even if it falls short of the perfection it pursues. New materials such as graphene and new methods such as 3D printing have properties and capabilities that may result in revolutionary change, to take just two examples. But at a cost in time and risk.

A question of time

The key contrast between the two approaches is in the results. The evolutionary approach enables the customers to make best use of available technologies to solve problems right away and the competitive pressure to meet customers’ needs more cost-effectively will drive continued evolution and innovation. The revolutionary approach leaves the customers waiting for a long time for a dream that may never come true while not addressing the current problems. The UK utilities will protest that they are addressing the current problems while the Designer Liner project is under way and that the OFWAT 3-hour rule precludes them from lining. But they are reported to have lined 20km of water mains in the current AMP period; that is a pitiful 0.005% of the total network length. I do not advocate abandoning innovative research and seeking better solutions. To do so would be absurd and genuinely valuable innovation can come from projects such as the Designer Liner. I sincerely believe and hope that they will. But the need is pressing; it is here and now – and so are the solutions. It is telling that the presentation of the Designer Liner project identified the barriers to new lining solutions in the UK water sector regulation, cost of market entry, lack of a consistent testing approach, and lack of definition of need. These make the market unattractive to new entrants and the Designer Liner in itself will not overcome them.

Address the barriers and the current solutions can be deployed to tackle and solve the problem of failures and water loss. They are cost-effective, durable, and environmentally friendly and can be deployed with minimal disruption. Were the UK water utilities to send a strong signal of consistent demand, i.e. a clear policy of mains rehabilitation (as has been the case in the gas sector) the suppliers would go through the Regulation 31 process and the full gamut of solutions would be available. This begs the question – what is stopping them?


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