Elastomer-bonded sealing materials that come in contact with drinking water need to be tested and certified. From March 1, 2025, a new guideline will be taking effect.
By Andreas Will and Oliver Zach, ESA
For organic materials that come in contact with drinking water, proof of suitability for drinking water hygiene must be provided. Products that were previously subject to the German KTW, coating, or lubricant guideline (German: KTW-Leitlinie, Beschichtungsleitlinie oder Schmierstoffleitlinie) have been assessed since 21st of March 2021 according to the assessment basis for plastics, organic coatings and lubricants in contact with drinking water. Silicones and TPE based on silicones shall also come under the scope of the application once the relevant annexes are supplemented.
In the case of elastomers, the confirmation of conformity in the past has been carried out in accordance with the elastomer guideline (German: Elastomerleitlinie). In March 2022, elastomers and thermoplastic elastomers have also been included in the KTW-BWGL, with a transitional period until the 1st of March 2025.
KTW-BWGL gradually replaces elastomer guideline
Please note that until the 28th of February 2025, it is still possible to prove the suitability of the elastomer-bonded sealing materials associated with the elastomer guideline test reports and microbiological growth according to W270, provided that they are not older than 10 years.
The certificates in Table 1 confirm the suitability for the use in drinking water in the transitional period. In the transitional period, it is always possible to initiate new tests according KTW-BWGL or re-assess elastomer guideline testing if requirements from KTW-BWGL are met.
The elastomer guideline for products in contact with drinking water is to be withdrawn on March 1, 2025. From then on, own conformity declarations in combination with a related third party KTW-BWGL test report from an accredited institute replace the so far known certificates.
The material ingredients must be toxicologically assessed by the accredited test institute. They are typically listed in the actual positive list of annex “D” of the KTW-BWGL. Here, the recent listing of the aramid fibre and various cross-link substances are specifically worth mentioning as supportive for the sealing industry. Optionally, the ingredients could be qualified directly through the institute without publishing them in the positive list. Please note that it is not required to replace installed sealing materials after the end of the transition period.
KTW-BWGL risk-based approach
In the KTW-BWGL, the risk of individual components in contact with drinking water within a plant for the production, treatment, or distribution of drinking water is estimated based on the assignment to various risk groups (P1, P2, P3). The classification is based on the fraction AB/A of the water-contacting surface of the component AB within the overall plant or component with surface A. Surface A is generally the cross section of the sealing component. Sealing materials are to be classified in the risk groups P3 (AB/A < 1 %) and P2 (1 % < AB/A < 10 %). The KTW-BWGL does also provide a simplified confirmation of conformity in the form of a type test for components in risk groups P2 and P3.
KTW-BWGL sealing materials classified as risk group P2
Required type tests for risk group P2:
- Ingredients assessment
- Migration tests
- Microbiological growth
Tests are required for all components in contact with water.
Certifiable components in water meters:
- Metals
- Plastics
- Elastomers
- Coatings
For the confirmation of conformity, previous test reports that were prepared in the context of issuing can still be used, if test certificates are in accordance with the corresponding guidelines. In risk group P3, there is no ingredient assessment required by a third party. Only compliance with the basic requirements like odour, cloudiness, colouring, foaming, TOC as well as microbiological growth must be ensured to continue using these components. Sealing material suppliers, do not have any responsibility for the suitability of all composite components or the assembled system.
About the author
Andreas Will is a chemical engineer with 26 years of experience in the gasket sector. He currently serves as R&D Manager of the Industry Division of Frenzelit GmbH.
Oliver Zach is a mechanical engineer with 28 years of experience in the gasket sector. He is a Director at Teadit International Produktions GmbH. Both authors are members of the ESA Flange Gaskets Division.
About this Technical Story
This Technical Story is an article from our Valve World Magazine, December 2023 issue. To read other featured stories and many more articles, subscribe to our print magazine. Available in both print and digital formats. DIGITAL MAGAZINE SUBSCRIPTIONS ARE NOW FREE.
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