Can I collect rainwater?
Yes — collecting rainwater is allowed everywhere, and for a new build or major renovation a tank is even compulsory. Just don't drink it. Collecting it for the toilet, washing machine, garden or cleaning is perfectly allowed and encouraged. In Flanders the Rainwater Regulation 2023 (in force since 2 October 2023) requires, for new builds and major renovations, a rainwater tank sized to the roof: 5,000 litres under 80 m² of roof, 7,500 litres up to 120 m², 10,000 litres up to 200 m², then 100 l/m². The rainwater must feed the toilet, washing machine and an outdoor tap, and on most plots an infiltration facility is also required. In Brussels a tank is compulsory for a new build or an extension over 20 m² of footprint (at least 33 l/m² of roof). In Wallonia there is no general regional obligation, unless your municipality or a flood condition imposes one. Drinking, cooking or showering with rainwater is inadvisable, and a fixed connection to the drinking-water network is forbidden.
📋 The rules
- Collecting rainwater for toilet, laundry, garden and cleaning: allowed everywhere
- Flanders (new build/renovation): a tank of 5,000 to 10,000 l by roof area, then 100 l/m²
- Flemish rainwater must feed the toilet, washing machine and outdoor tap; usually an infiltration facility too
- Brussels: tank required for a new build or extension > 20 m² footprint, at least 33 l/m² of roof, plus a tap and a WC
- Wallonia: no general regional duty — check your municipality or a flood condition
- Do not drink it: a fixed connection to the mains is forbidden; networks must be separated and inspected
🔓 Exceptions
- Existing house without works: no compulsory tank, collecting stays free (water butt, existing cistern)
- If a tank is already present during a renovation, no second one is needed
⚠️ Penalties & fines
The tank and infiltration are permit conditions: missing them on a new build or renovation risks an unfavourable opinion or a refused permit, and the water-installation inspection is failed until the infiltration is in order. A forbidden fixed connection to the mains is also failed. The regulation itself sets no separate fine; enforcement runs through the planning and inspection rules.
📎 Official sources
- Departement Omgeving Flanders · Rainwater Regulation 2023 →
- VMM · using rainwater safely →
- Bruxelles Environnement · rainwater management →
❓ Frequently asked
Can I just put out a water butt?
Yes, always and everywhere, even without works. The compulsory tank with fixed connections applies only to a new build or a major renovation.
How big must my rainwater tank be?
In Flanders it depends on your roof: 5,000 l under 80 m², 7,500 l up to 120 m², 10,000 l up to 200 m², and 100 l per m² above that. In Brussels reckon at least 33 l per m² of roof.
Can I drink rainwater?
Better not. Rainwater is not clean enough to drink, cook with or shower in — that needs drinking-water quality. And a fixed connection between rainwater and the mains is forbidden.
Do I also have to infiltrate my rainwater?
In Flanders an infiltration facility is nearly always compulsory when building or renovating, except on very small plots (under 120 m²). In Brussels the zero-discharge-to-sewer principle applies.
🔎 Common searches
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