“Keeping things as they are” is not an option…

A personal viewpoint on compliance with the generally recognized rules of technology, a new mod. ZTV, the DIBt and the way out of the dilemma…

Dipl.-Ing. Jörg Brunecker / Managing Director
Swietelsky-Faber GmbH Kanal Sanitation
Am Kaiserkai 69, 20457 Hamburg

More than 50 years ago, the first cured-in-place pipe liner was installed in London, and to this day it has advanced from a niche product to a globally recognized standard product for the rehabilitation of our underground infrastructure, thanks to continuously improved materials and equipment technology as well as an internationally valid set of regulations.

As the responsible representative of an executing company that operates various pipe rehabilitation technologies, in addition to single-pipe lining, winding-pipe lining, and close-fit lining, we install over 4,000 CIPP liners of all kinds annually, with an increasing trend. In the UV-curing sector, we installed goods worth over €10 million in Germany alone in 2025.

However, in some circles this very liner has become the subject of discussion, which in my view should be examined from a different perspective. For, in my assessment, this endless discussion is only the effect of a matter, and in this report I would like to address the cause of the debate. With 30 years of industry experience, which is accompanied by many years of association activities and standardization work and also includes good access to the liner industry, I can classify the cause of the dilemma and would like to offer possible solutions.

Because, in my view, the problem stems on the one hand from the fact that many parties involved in the liner industry have lingered in a comfort zone for far too long and, in recent years, have simply neglected, for various reasons, the actual implementation of the state of the art and customer sensitivities. On the other hand, fueling such a debate increases attention and, in some eyes, possibly even market reputation, which one can use to make a splash on event stages. So if we examine the cause of the discussion, the multifaceted background quickly becomes apparent; a multi-layered analysis is called for. So I will start with the DIBt.

Although this may seem unfamiliar to some market participants, our internationally standardised pipe liner no longer requires an explicit certificate of applicability under the state building regulations. Especially since the model building code, on which all state building regulations are based, has long excluded the pipes of public wastewater disposal from its scope for good reason (MBO §1 Scope). Thirty years ago, it was different. But just because that was the case yesterday does not make it right today.

Therefore, the DIBt approvals for our area of work derive their legitimacy from customary law. Those responsible in Berlin are aware of this too, and accordingly very little staff is assigned to our area. The relevant advisory board meets once a year, ambiguities become time-barred, and the DIBt processing steps take an extremely long time. Installation manuals and DIBt approvals differ outrageously from one another. In the end, our DIBt approvals degenerate into nonsensical money-making and no longer serve the purpose, but rather act as an anachronistic obstacle to competition.

As already said, our market still calls for approvals out of habit, but through targeted and technically sound public relations, all parties involved could be convinced of the absurdity of the DIBt approvals. What would be necessary for this, however, is that the manufacturing and executing companies have themselves audited with regard to DIN EN ISO/TS 23818-2. They have to do it anyway, because this corresponds to the generally recognized rules of technology, and our planners and clients should also demand this proof of suitability and quality.

I can only recommend this to every client, because the test programmes of ISO/TS 23818 are significantly more detailed and comprehensive in production and installation than the previous suitability verifications. Special profiles are thus no longer in the grey area of application fields. Good for our testing institutes, good for our clients and, ultimately, good for the final product, the hose liner.

But out of habit and often self-serving sensitivities, one has not yet cut off the braid. Unfortunately, one does not act in accordance with the recognized rules of technology and ignores innovation… However, this is only part of the cause of the dilemma.

Because, in addition, the industry associations have set themselves the goal of closing the gaps in the regulatory frameworks. Very commendable, but apart from the highly committed employees in the association committees, the association officials (DWA, VSB, RSV) have viewed the task more as marketing for their own benefit and, beyond that, have devoted themselves to interminable association disputes in the preparation of the working papers. Harmonising the rules of technology is, after all, rather irrelevant for member recruitment (they think so; however, I see it very differently...).

Result: Instead of having closed gaps, we are wandering through a homemade jungle of rules. For from Castrop to Rauxel alone we have different supplementary technical contract conditions, requirement profiles, standard texts, and need various regulations just to line a sewer... A situation that stands in the way of the generally desired reduction of bureaucracy. In addition, we should honestly take a look at ourselves, because only a few tenders are planned ready for execution and the claims vultures are circling around the projects, few awards comply with the requirements of VOB/A, only a few site supervisors shine with a presence on site, hardly any liner manufacturer has done its homework on the standard statics taking into account the new strength values according to ISO-11296-4. Some do not even know the draft standard of ISO 11300. To this day, no liner manufacturer is willing to declare to us executing companies the styrene content of the liners at goods issue. Regardless of the fact that the styrene contents demonstrably show significant tolerances and this is clearly relevant to the curing degree of the final product. Furthermore, some representatives of the liner industry are so busy selling the liners abroad that they completely ignore the concerns of our customers here. Fitting for Carnival, a person from Cologne would say: „Know not, need not, away with it, because it has always gone well so far...“

But in terms of the matter - that is, for the future-proof preservation of the value of our infrastructure, we cannot get any further with faulty mod. ZTVs from private hands and the shortcomings described above. However, they underline the dilemma: because apparently everyone does what they want, no one does what they are supposed to, and everyone joins in...

Even though some approaches of the mod. ZTV-Schlauchlining are usable, I am convinced that the market for cured-in-place pipe lining does not need any further association standards. And certainly not if they do anything but bring clarity to the jungle of standards and even inadequately take the recognised rules of technology into account. A few examples...

1. For good reasons, DIN 53394-2 for styrene measurements was withdrawn in 1993. It is simply negligent to use an invalid standard and not to carry out residual styrene measurements according to ISO 4901. No judge will accept such disregard for the recognized rules of technology.
2. I do not understand why the use of an integrated anti-slip film should not be permitted,
3. ...why the provisions of ISO 23818-2 were ignored in the mod. ZTV,
4. ...why the ZTV contains no references whatsoever to sustainable procurement criteria and instead promotes an obsolete strategy (more material use = longer service life),
5. The storage and temperature monitoring are described in such a misleading way between the technology families and are finally rendered absurd by a manufacturer’s declaration.
6. Unacceptable wall thickness tolerance specifications – which shift an unreasonable execution risk onto the executing companies and thus unnecessarily increase the cost of the final product,
7. ...why static recalculations should no longer be permitted,
8. ...why municipal contracting authorities develop a mod.-ZTV, which is then sold by a private entity for €250 per item.

The recognized rules of technology are not a private matter, however, and all the other craftsmanship errors of the mod. ZTV that are not mentioned here would be corrected with the hundreds of employees in international standardization. But if we continue like this, we should not be surprised by the startup companies that reinvent the wheel with good marketing, or by all the well-intentioned but market-unsettling specialist articles.

I have great understanding for the client side, which has more or less contributed to the revised ZTV, and I do not regard this action negatively at all, as some others do. Rather, I regard it as a wake-up call – and that is a good thing, because a “carry on as before” is not an option... So let us finally address the cause together. In my view, the general market irritation arises essentially from the unclear situation surrounding compliance with the rules of engineering and the disregard for our customers’ concerns regarding the sewer liner. Resolving this is not that complicated. Leading figures in the liner industry have already assured me that they will now have audits carried out according to the production criteria of ISO 23818-2. One has already done so. The test parameters and intervals are a step in the right direction toward meaningful quality assurance.

If the association officials are now also prepared to clear away the jungle of regulations and direct their focus toward cooperation with the relevant regulatory bodies, we will clearly be able to keep our cured-in-place pipe on course. The construction companies will promptly have themselves audited according to the installation criteria of ISO 23818-2, but some may only do so if the client makes this quality certificate a tendering criterion. I would do it…