DS 439:2024 is the first real technical revision of the water standard in nearly 50 years. The simplified dimensioning method is abolished, dimensioning now takes place via the qd method, and there is a tightened requirement for pressure testing of empty pipes before they are hidden. Here are the main points you need to know.
Introduction
DS 439 is the standard for water systems in Denmark — it sets out how a drinking water system is dimensioned, which materials can be used, and how the system is tested and flushed before use. Following DS 439 is the recognised way to comply with the Building Regulations' requirements for water systems.
The simplified method has been abolished
Previously, smaller installations could be sized using a simplified one-step method. This has been removed in the 2024 version — sizing must now be done using the full method with design water flow (qd). This means you always have to sum the expected water flows and calculate the flow through.
Dimensioning water flow qd
qd is the flow the pipe really must be able to carry when taking into account that not all fixtures are used at the same time. The fixture-specific normal flows (qf per fixture type) are in the standard itself — they are not reproduced here because they are behind the Danish Standard paywall and must be retrieved directly from webshop.ds.dk.
- 01Recommended max water velocity is approximately 1 m/s – it reduces biofilm and flow noise (industry practice/Viega, advisory).
- 02Material choice must avoid galvanic corrosion; combine only identical or approved materials.
- 03DS/EN 1717 on backflow protection is referenced from DS 439 — protection type is selected according to fluid category.
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