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.
Design late = redesign
How Caskade helps
Design-to-permit: feasibility, sizing and documentation prepared for licence approval, in line with the Ordinance.
Turnkey delivery: engineering, supply, installation and commissioning with maintenance and testing protocols.
100 % financing: zero upfront investment — pay per m³ reused with our Water-as-a-Service (WaaS) model.
Operation and monitoring: real-time telemetry and testing programme for hassle-free audits.
