Technical documentation

Under the Drinking Water Directive (DWD) and its implementing regulations, every manufacturer placing a product on the EU market must prepare and maintain Technical Documentation (TD). In short, this is the evidence that demonstrates compliance.

What must be included?

At a minimum, if we follow the exact text of Decision 768/2008 the TD must contain:

• a general description of the product,
• conceptual design and manufacturing drawings and schemes of components, sub-assemblies, circuits, etc.,
• descriptions and explanations necessary for the understanding of those drawings and schemes and the operation of the product,
• a list of the harmonised standards and/or other relevant technical specifications applied, and descriptions of the solutions adopted to meet the essential requirements where those standards have not been applied,
• if standards were applied only partly, a specification of the parts which have been applied,
• results of design calculations, examinations carried out, etc.

And it must make it possible “to assess the product’s conformity with the applicable requirements … and shall include an adequate analysis and assessment of the risks.”

Unfortunately that does not help us much. The Technical Documentation, in a nutshell, must allow anyone reviewing it (in particular a Notified Body) to assess the conformity of the product with the applicable DWD requirements. It should also include a risk analysis, details of design, and how the product is manufactured and operated.

While the legal text sounds abstract, in practice TD boils down to all the documents someone would need to check if your product complies. For most DWD products, this typically includes:

• Formulation reviews (to demonstrate compliance with the EU Positive Lists).
• Migration test reports according to Decision (EU) 2024/368.
• Certificates of pre-products, intermediate products, or components (if applicable).
• Bills of materials and supplier declarations.
• Quality management documents relevant to Module C or D.
• The EU Type Examination Certificate (Module B).
• Risk assessments and supporting calculations.
• Description of the product and design documentation.
• Formulation list.
• Wetted surface calculations (for assembled products, for each component).

How should manufacturers handle it?

Think of the TD as a living compliance file. It is not one document, but a collection of everything you have on the product. However, it is extremely helpful to organise these materials into a structured dossier (e.g. through referencing) — especially when dealing with a Notified Body. Presenting test reports, certificates, and declarations in a consolidated format makes the assessment smoother and avoids delays.

Confidentiality of suppliers?

One of the most common challenges for manufacturers under the DWD is dealing with confidential supplier information. Many components rely on pre-products or intermediate products (such as polymer granulates, resins, or coatings) where the formulation is proprietary. Suppliers rarely want to disclose this to manufacturers.

The system has anticipated this. The Notified Body can approach the supplier directly under confidentiality agreements to verify compliance. However, this only works efficiently if the manufacturer prepares the ground.

What you should do in practice:

• Obtain a statement of intent from the supplier confirming willingness to cooperate with the NoBo or authorities.
• Secure contact details of a responsible compliance officer at the supplier.
• Secure a Letter of Access (LoA) allowing the Notified Body to request confidential details directly from the supplier.
• Ensure the LoA covers potential requests from Market Surveillance Authorities (MSAs).

This way, the manufacturer does not need to hold every confidential detail, but must be able to show that the supply chain is legally tied to the compliance process.

One caveat: supplier confidentiality

Imagine you are a large EU chemical company and a customer asks: “We need your full formulation for DWD compliance.” Your instinctive answer: No way. But without that information, the customer cannot complete conformity assessment.

This has always been an issue — also under the 4MS system. The Directive requires manufacturers to prove that every material meets the positive lists and passes migration testing. So the supply chain must open up — but only to the Notified Body.

To make this work, the downstream manufacturer must prepare paperwork in advance:

• Statements of intent from suppliers.
• Compliance contact details at the supplier.
• Letter of Access allowing the NoBo to obtain information directly.
• An LoA clause covering future MSA audits.

With this approach, suppliers protect their secrets, manufacturers get their compliance, and Notified Bodies can assess products properly.

Bottom line

The TD is your evidence trail. If a Notified Body or Market Surveillance Authority asks tomorrow, you must be able to show that your product was designed, tested, and manufactured in line with the DWD. The better you organise this documentation, the easier compliance becomes.