Generally no with some small exceptions:
A Module B certificate is issued for a type — a representative sample that has been tested and approved. To avoid unnecessary duplication, the system allows several products to be grouped into a product family if they are:
Produced from the same formulation or composition,
Manufactured under the same production process, and
Only differ in aspects that do not affect migration or hygienic performance (for example: size, length, or diameter within a defined range).
This concept is also mentioned in the guidance: if the smallest diameter pipe from a family is tested and approved, the whole series of larger diameters made from the same pre-product and process can be covered under the same certificate.
Examples
Pipes: If a manufacturer produces a full range of polyethylene service pipes from DN 10 to DN 300 using the same resin and extrusion process, testing the smallest diameter may cover the entire family.
Fittings: A series of brass compression fittings of different sizes, made from the same alloy and coating, can be grouped under one Module B certificate.
Assemblies: Product families may include an assembled product line (e.g. a range of taps of different shapes) as long as the internal wetted materials and processes are identical.
Where It Doesn’t Work
You cannot group products together if they:
Use different formulations (different resins, additives, alloys).
Are made under different production methods (e.g. injection moulded vs. extruded).
Introduce new materials/components not already part of the certified type.
In these cases, you need either a separate Module B certificate or an extension of the existing one.
The Bottom Line
Yes, product families are possible — and encouraged — under Module B certification. They help reduce testing and certification costs by covering a whole range with one representative type. But the golden rule is consistency: the products must share the same formulation, material, and production method. Differences that could affect migration performance or compliance with the DWD require their own approval.