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Siegel “Geprüfte Qualität”

Siebert + Knipschild awards the seal “Endprodukt Schlauchliner – geprüfte Qualität” annually to contractors who have done good work with a particular system for over a year. The test results of various projects of one year that we have received are decisive. All information, applications, documents and info can be found on this page.

Video: that’s how the seal works (German language)

declaration of the seal
in 60 seconds

Are you an executing company? This is how you apply for the seal:

  1. Site samples were tested through Siebert + Knipschild geprüft?Than you may belong to the potential award winners. Here you can find all impotant informations. 2019_award conditions_20180920
  2. You comply the criterias? Perfect. Please fill out the request for the seal and send it to us per Fax or E-Mail. Request_Seal_2019 (fillable PDF) You don’t know if you comply with the criterias? That doesn’t matter we will check it for you.
  3. You didn’t arrange the test by yourself? We need a declaration of consent to use the operators test results so that we can use the the anonymous datas. declaration of consent_2019 (fillable PDF)
  4. You want to show your clients what statement stand behind the quality assurance seal? Feel free to send him those informations. 2019_info_auftraggeber (PDF)

Previous seals (2015-2018)

Image module

Seal: “trenchless sewer renovation – tested quality”

Information at a glance

Since 2015 Siebert + Knipschild GmbH awards the seal “certified quality“.

To whom the seal is adressed:

  • The seal of quality certifies the executing company a product-related qualitative execution of the renovation. It summarizes product-related inspection data collected over the year
  • It serves the user and client as proof of the quality of the liners installed within one year.
  • The basis for this are the test results from a large number of liners installed under conditions equivalent to those on the construction site.


Do you have any questions about the seal? You would like to know how you, as an executing company, can receive a seal?

We are happy to answer your questions. > contact us


At the center of the seal is the final product Schlauchliner. The Siebert seal is therefore primarily a proof of quality for the executing company. Other features:

  • The seal is not intended for manufacturers of precursors. The awarding of the seal always takes place to the executing company in connection with a specific product . This documents the experience of an installation company with a CIPP liner system.
  • A seal is only given at the request of the installing company </ strong> (see form). Decisive are samples of pipe lining projects from January to December of a full, expired year. The award of the seal looks at the data from samples from the previous year.

It goes without saying that details of the test results as well as of individual projects are not published by Siebert + Knipschild to third parties.

Awarding criteria

  • The minimum number of samples  tested at Siebert + Knipschild in a calendar year, per contractor and product used: 20
  • All samples must come from at least four different trenchless rehabilitation projects.
  • The seal is awarded at a rate of 95 percent of those samples that meet the requirements. The characteristic values refer to the requirements according to the respectively valid approval for modulus of elasticity, flexural strength and watertightness . The wall thickness we check if the requirements are met according to the order.
  • If deviations are detected, the assessment of the build-in success takes place taking into account the second sampling.
  • The evaluation will take into account test samples submitted for by the contractor as well as clients . The consideration of the results from network operators require a special approval.

Q & A