Scrapers
Rod seals
Piston Seals
Guide rings
Back-Up rings
O-Rings / X-Rings
Flat seals
Spring-loaded seals
Radial shaft seals
Rotary seals
High pressure seals
Sealing sets
O-ring measuring towers
Turned parts
Milled parts
Turned and milled parts
Bushes or bearings
Moulded parts
Large format 3D printing
Post-processing of 3D printed parts
Heat-resistant 3D printed components
Plastic Components with Flame Retardancy
DVGW W270
Definition and Purpose of DVGW W 270
DVGW W 270 is a technical code of practice issued by the DVGW (German Technical and Scientific Association for Gas and Water). It describes a standardized test method that evaluates whether a material in contact with drinking water promotes the growth of microorganisms on its surface. This property is often referred to as biofilm tendency. A biofilm is a layer made up of microorganisms and their metabolic products that can form on surfaces in aqueous environments.
The purpose of the test is hygienic: materials in drinking-water installations should encourage the formation of such layers as little as possible. This is particularly relevant for materials that contain organic constituents or consist of organic polymers, because these can, under certain conditions, create a more favorable “adhesion” or “nutrient” environment for microorganisms. In practice, this often concerns plastics, elastomers (rubber-like materials such as seals), as well as coatings and composite materials.
In the market, the 11/2007 edition is widely used; according to common reports, it was reviewed in terms of content and confirmed in 09/2023.
Scope: Material, Component, Product
In many cases, DVGW W 270 is carried out as a material test. Standardized specimens or defined material samples are then tested in order to evaluate the basic behavior of a material.
Sometimes that is not enough, because a real component brings additional influences with it — for example, layered build-up, manufacturing residues, or special internal geometries. In that case, a product test can be sensible or even required, so that the actual surface in contact with drinking water is captured realistically.
| Test object | What is captured? | When is it practical? |
|---|---|---|
| Material specimen | Material baseline behavior (formulation/matrix) | Often suitable for homogeneous materials |
| Product/component | Surface, layers, geometry, manufacturing condition | Frequently for multilayer systems or complex internal geometries |
What Is Tested and What Is the Evaluation Principle?
The test evaluates how strongly microorganisms multiply on the surface of a material under practice-near conditions. As a result, it targets surface colonization — the build-up of biomass on the material. The evaluation is usually carried out as a comparison with a reference material considered uncritical; in explanatory descriptions, stainless steel is often cited as such a reference. What matters is the relative behavior: a material should not show a clearly elevated biofilm tendency compared with the reference level.
In practice descriptions, unchlorinated drinking water is frequently mentioned, in order to reflect the situation in installations without a continuous disinfection effect. Likewise, a multi-month test duration is often referenced, because biofilm formation is a time-dependent process. The specific operating conditions, measurement variables, and acceptance criteria are defined in the original code of practice and should always be consulted directly for a robust assessment.
Distinction: Surface Colonization vs. Substance Migration
DVGW W 270 primarily addresses the microbiological colonization of the surface. It is not primarily about detecting specific pathogens, but about the fundamental tendency of a material to promote microbial growth.
Other hygiene-relevant topics sit alongside this and are addressed in separate codes of practice. These include in particular:
- Substance migration: transfer of chemical constituents from the material into the water.
- Sensory effects: changes in odor and taste.
These properties can be just as important for drinking-water products, yet they are not the core of W 270.
Context: KTW-BWGL, UBA Requirements, and Further Test Requirements
In the drinking-water context, DVGW W 270 is frequently considered together with requirements for material suitability. In Germany, the KTW-BWGL (Assessment Basis for Plastics and Other Organic Materials in Contact with Drinking Water) plays a central role. While W 270 addresses microbiological surface tendency, the KTW-BWGL primarily evaluates chemical aspects such as migration and, in part, sensory effects.
Until full EU-wide harmonization, requirements and assessment bases of the UBA (German Environment Agency) are also referenced as part of drinking-water regulation in Germany. In practice, a comparison with positive lists is common. Positive lists specify which starting substances or material constituents may be used under defined conditions.
Which Verifications Are Typically Combined
For manufacturers and users, this typically results in a package of multiple verifications, because drinking-water hygiene consists of several dimensions. The following building blocks are therefore frequently considered together:
| Verification type | Target property | Typical practical benefit |
|---|---|---|
| DVGW W 270 | Biofilm tendency (microbiological surface colonization) | Assessment of microbiological surface behavior |
| KTW-BWGL / UBA assessment bases | Migration, material suitability, partly sensory effects | Chemical hygiene and material conformity |
| Positive-list comparison | Permissibility of constituents | Safeguarding the formulation/material selection |
Practice in Sealing and Hose Technology: Materials, Formulation, and Documentation
In sealing technology, DVGW W 270 is particularly relevant, because many sealing materials are organic and come into direct contact with drinking water. Typical applications are O-rings, flat seals, membranes, and sealing lips, as well as inner layers of hoses and coated components. Composites in which several material classes interact can also be affected.
The formulation (compound) of an elastomer or plastic influences behavior in contact with water. This includes fillers, plasticizers, additives, stabilizers, and curing agents. Even small changes can alter the surface, leaching processes, or adhesion properties — and thereby indirectly also the biofilm tendency. Therefore, in supply chains for drinking-water applications, it is common to clearly define formulation states and strictly control changes.
For documentation, several levels are frequently expected: a test report or test certificate for the W 270 assessment, a comparison with positive lists, and information about the formulation. Formulation disclosures often take place under a non-disclosure agreement (NDA), because the compound represents a substantial part of the know-how.
When a Product Test Is Sensible (e.g., Multilayer Systems)
A product test is particularly sensible when the surface in contact with drinking water cannot be described by a single homogeneous material. This is often the case with multilayer hoses, coatings, co-extrusions, or when adhesive and primer layers are involved. Geometry can also become relevant, because it influences flow, deposits, and therefore local biofilm formation.
When it is unclear whether a material test is sufficient or a system verification is required, an early alignment with the test laboratory and quality management pays off. Specialized consultation can help to plan test effort and verification strategy in a focused way.
