Be on the safe side with KTW hygiene certification 1+

The quality of the drinking water that flows from taps across Germany is excellent. Besides water quality, also other factors play an important role including the material of pipes, fittings and other components that come into contact with water. In Germany, the Umweltbundesamt (German Environment Agency) is authorised to stipulate evaluation criteria to assess the hy-gienic level of materials that come into contact with drinking water. In future, there will be an official system to replace the current non-binding KTW guidelines, which will be legally binding from March 2021 after a transition period. Manufacturers, companies and water suppliers want to know what this means for their products. 

Drinking water must be protected against undesirable substances

According to the German Drinking Water Ordinance (Trinkwasserverordnung TrinkwV), materials used to construct or maintain systems for the extraction, treatment or distribution of drinking water and those in contact with drinking water must not:
- directly or indirectly reduce the protection to human health
- adversely change the odour or taste of the water, or
- allow substances to pass into drinking water in quantities beyond those which are unavoidable when complying with the generally accepted technical regulations.

These general requirements have been substantiated for organic materials, particularly in the guidelines of the German Environment Agency and in terms of microbial growth in the DVGW worksheet W 270. The German Environment Agency’s guidelines for organic materials are also summarised under the umbrella term “KTW guidelines”. It is not strictly mandatory to use the KTW guidelines, however, product certifications in particular make them necessary. When certifying products for use with drinking water, certification bodies that are accredited for the drinking water sector, such as DVGW CERT GmbH, require evidence of hygienic safety, provided by the results of testing in line with the KTW guidelines. There is no specific requirement to date for certification that solely evaluates adequate hygiene. 

New assessment criteria plus hygiene certificate for plastics

On 21 March 2019, the German Environment Agency published assessment criteria for plastics and other organic materials in contact with drinking water (KTW-BWGL) (Link to the document, only in German). The KTW-BWGL is intended to gradually replace the previous KTW guidelines for organic materials. Its scope currently covers plastics, organic coatings and lubricants. As well as a general section, the guidelines contain a polymer-specific section with a positive list of the substances that may be used to produce the various organic materials. The KTW-BWGL becomes legally binding from 21 March 2021. At the same time as the KTW-BWGL were published, the German Environment Agency published its recommendation, attestation of conformity of product hygiene suitability for drinking water (Link to the document), which describes a method that can be used to demonstrate conformity and therefore receive a (hygiene) certificate. Relevant certification programmes have been established by DVGW Cert GmbH based on this recommendation, which can be followed to obtain a hygiene certificate once compliance with all requirements is achieved (Link to the document ZP 1000), (Link to the document ZP 0800) .

Pipes and equipment require KTW 1+ system

The new certification procedure can be used for components such as mechanical filter housing and for compound products containing components made from organic materials such as mechanical filters with all the individual components. Pipes and equipment such as fittings and valves are subject to the highest testing requirements according to the KTW-BWGL and certification according to the German Environment Agency’s recommendation. The reason behind this is that they comprise the vast proportion of the surface area in contact with drinking water in a drinking water distribution system. These products are classified as risk group P1 according to KTW-BWGL. Group P1 products or components must be certified according to the “1+ system”. The 1+ system involves:

  • Initial inspection of the plant and sampling
  • Type testing
  • In-house production control (in-house monitoring) and
  • Annual monitoring tests (third-party monitoring).

Previously, the KTW guidelines required only type testing. The awarded test certificate was then also used as evidence of conformity. Type testing is just one element in the new 1+ system, which also includes inspections and monitoring. The attestation of conformity is awarded by an accredited certification body based on testing and inspection reports.

From a practical perspective, type testing remains the same as before and is conducted according to DIN EN 12873-1 or, for microbial growth, according to DIN EN 16421, method 2 (identical to DVGW W 270 testing). The hygienic suitability of drinking water continues to be based on requirements on the formulation, basic and additional requirements, formulation-specific requirements on individual substances and a requirement concerning microbial growth.

Products with smaller surface areas in contact with drinking water are subject to simpler procedures to obtain the attestation of conformity: a type testing-based certification procedure for P2 products or a manufacturer’s self-declaration based on a KTW-BWGL test report for P3 products. The latter procedure omits the initial plant inspection and does not include any annual third-party monitoring.

TZW Test Centre is accredited for the new system

Product manufacturers are not obliged to obtain certification, however it is possible to acquire a certificate, as stated explicitly in section 17 of the German Drinking Water Ordinance, which attests to compliance with material requirements. A certificate issued by an accredited body is held in much higher esteem than other forms of conformity declarations. And this is increasingly the case when extensive testing and inspections are performed on the product and in the production site to obtain a certificate. These can only be performed by auditors and inspectors with appropriate qualifications – such as those who work at the TZW Test Centre.    

The TZW Test Centre is already accredited as a testing laboratory for testing according to KTW-BWGL. What’s more, it can provide inspectors commissioned by the certification body to perform specialist audits for the initial plant inspection and the annual monitoring tests.