Blog · Published September 17, 2025 · 3 min read
Barcelona: 2026 Greywater Ordinance
If you plan to build or renovate in Barcelona, take note: from July 2026 your project will not get a licence without a greywater system.
From 19 July 2026, all new buildings and major renovations must include greywater systems (showers/bathtubs) for toilet flushing, drip irrigation and street washing. If your project falls under these rules and the system is not included in the basic project design, the licence will not move forward.
Who does it apply to?
- Residential: buildings with 16+ dwellings in new builds or in major renovations involving replacement of the building (even if the façade or some structural elements are preserved).
- Commercial and other uses (hotels, offices, gyms, etc.): if water consumption for toilets + drip irrigation + street washing is ≥ 595 m³/year in new builds or major renovations.
How it works
- Mandatory collection: showers and bathtubs.
- On-site treatment: filtration/biological or membrane systems, with disinfection, to meet the quality standards required by the ordinance.
- Uses of the treated water: toilets, drip irrigation and street washing.
Deadlines and paperwork
- In force: 19/07/2026 (one year from the day after official publication on 18/07/2025).
- For building works licences: the basic project must include the system with sizing calculations and technical documentation; without this, the application will not advance.
Operation and control (the minimum)
- Technical standard: UNE-EN 16941-2:2021 (design and O&M).
- Water quality: half-yearly tests (E. coli, turbidity, chlorine, pH); RD 487/2022 if aerosols (street washing) are involved.
- Documentation: Final Certificate (Annex 3) and Maintenance Book (Annex 4) with protocol and records.
Impact – why plan now
Up to ~33 % less potable water in residential use; ~136,000 m³/year saved across the city. Expected coverage: 70 % of residential projects (new build or major renovation) and 100 % of hotels (Barcelona City Council).
Design late = redesign
plumbing and technical rooms
Why Caskade
Compare first.
Every site and effluent is different. And yet, manufacturer proposals are built to sell a standard solution, not to compare the options.
Caskade finds the optimal solution for each site and effluent, evaluating 5+ technology routes and 30+ manufacturers on one baseline.