CIPP Rehabilitation Seal of Quality

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

Seal of Quality news

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Video: How the seal works in 60 seconds (German language)

How the seal works
in 60 seconds

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

  1. Your site samples were tested by Siebert + Knipschild? Then you may be among the potential award winners. Here you can find all impotant information. 2019_award conditions_20180920
  2. You fulfill the criteria? Great! Please fill out the request for the seal and send it to us via Fax or E-Mail. Request_Seal_2019 (editable PDF) You don’t know if you comply with the criterias? That’s okay – we will check for you.
  3. You did not arrange the tests by yourself? We need a declaration of consent to use the operator’s test results so that we can use the the anonymous data. Declaration of consent_2019 (editable PDF)
  4. You want to show your clients what the seal of quality stands for? Feel free to send them this information: 2019_info_auftraggeber (PDF)

Seal: “trenchless sewer renovation – tested quality”

Information at a glance

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

Who is the seal for?

  • Executing companies use the seal of quality to certify the qualified execution of renovations using the specified product. 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 the conditions of construction sites.


Do you have 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


The CIPP liner is the focus of the seal of quality. It is therefore primarily a certification of quality for the executing company. Other aspects of note:

  • The seal is not intended for manufacturers of precursor materials. The seal is always awarded to the executing company in connection with a specific product. This documents the expertise of an installation company with a CIPP liner system.
  • A seal is only given at the request of the installing company (see form). It is decided based on samples of pipe lining projects from January to December of a full, expired year. The awarding regards 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

Which critera form the basis in awarding the seal?

The seal is awarded to executing companies whose samples from the previous calendar year were tested at least 95 % positive. The requirements in terms of wall thickness, modulus of elasticity, flexural strength and watertightness must be fulfilled for the respective sample. The minimum number is 20 samples of the respective system submitted. All specimens must come from at least four different construction measures. If deviations are found, the evaluation of the executing company will take into account the second sampling.

 What is the advantage for clients planning a pipe lining project if an executing company bears the seal? 

The client obtains the assurance of working with a company that has successfully proven its experience with the respective product at a high quality level. The seal is issued by a qualified and independent body – Siebert + Knipschild is an accredited testing institute with more than 30 years of experience in quality assurance for pipe lining.

What is the advantage of the seal for an installation company that has submitted samples?

The installing company is ultimately responsible for the quality of the end product. With this seal, it can show a potential customer that it has done a good job in the past – always in relation to the respective pipe liner system. This also sends out the message that the organization, equipment and qualifications of the employees are right.

In what capacity can companies use the seal?

Companies have the option of using the seal for their communication with customers. For example, they can display the seal on their website or use it for printed customer information. The corresponding printable graphic file is provided by us. It must not be modified, as, for example, the liner that is decisive for the awarding of the seal is noted on the seal.

Can a company receive multiple seals?

Since the seal is only ever awarded in conjunction with a specific pipe liner system, a company can receive multiple seals if it installs more than one system.

How does an installation company obtain the seal?

Once the criteria have been met, companies can apply to us for the seal. There is a corresponding form for this purpose. If we determine that the criteria have been met, we will contact you and enclose the relevant information or the application form in addition to the test report.

What if an executing company / product does not have a seal – do I as a client receive information about the reasons from you?

No. Even if the reason is only that the company is not a customer of ours, we are not allowed to give out such information.

As a client, I would like to receive more detailed information about the data, for example, how many samples were submitted and what the exact percentage is. Where can I get this information?

The seal is to be seen as a visible reference based on statistical data from test reports. The right to use this data lies with the client of the test report. As a test laboratory, we are of course not allowed to release this data.

When is the seal awarded?

The seal award considers the data of samples from the past year. The seal states the year in which it was awarded. If a company meets the criteria in the current year, interim statistics can also be made if resources are available, and the seal can be awarded during the year.

What are the costs?

We charge the applicant an administration flat rate of 250.00 euros plus VAT per seal for compiling the documentation. Seal holders receive detailed statistics on all tests carried out and a list of all test results determined for the entire previous year, as well as an aluminum plaque with their logo and the current seal.