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Water

Is a rainwater tank mandatory?

Short answer

For new builds and major renovations in Flanders since 2 October 2023: at least 5000 litres, more for larger roofs, and the water must be reused.

Rainwater tank by roof area: Flanders, new builds and major renovations: 5000 l for a roof up to 80 m², 7500 l above 80 m², 10 000 l above 120 m².
Rainwater tank by roof area — Flanders, new builds and major renovations: 5000 l for a roof up to 80 m², 7500 l above 80 m², 10 000 l above 120 m². (The text inside the figure is in Dutch.)

Explanation

Flanders wants to retain and reuse rainwater for longer. The regional urban planning regulation on rainwater sets volumes and reuse for this. You do not have to replace existing tanks.

Rules of thumb

  • Applies since 2 October 2023. [SW-S42]
  • At least 5000 litres. [SW-S42]
  • Roof larger than 80 m²: at least 7500 litres. Larger than 120 m²: at least 10 000 litres. [SW-S42]
  • Reuse is mandatory, for example for the toilet, cleaning water or washing machine. [SW-S42]

Pitfalls

  • Rainwater is not drinking water: separate pipes and clear marking are needed. [SW-S42]

By region

Flanders
Rainwater regulation 2023; checked via the environmental permit. [SW-S42]
Netherlands Wallonia Brussels
Other rules; not covered in this version. [SW-S42]

Search terms

These search terms are in Dutch; only terms that also find a topic in English are links.

regenwaterput hemelwater nieuwbouw hergebruik

Read also

General information, not personal advice. Check the source and reference date.

Not legal advice. Rules differ by country and region; consult the competent authority.

Sources

  1. SW-S42 Grotere regenwaterput verplicht bij nieuw- en verbouw vanaf oktober 2023 — Vlaamse Milieumaatschappij (VMM) (Reference date 2026-09-27)

Reference date: 2026-09-27 · Translated with AI from the Dutch original.