New National SuDS Standards 2025: What Every Developer Needs to Know

The drainage design landscape has fundamentally shifted with the introduction of National SuDS Standards.

After over 40 years in drainage design, I can confidently say this represents the most significant change to sustainable drainage requirements we've seen. The new hierarchy doesn't just change how we design—it revolutionises our entire approach to water management.

The Game-Changing Hierarchy

The most critical change is the new runoff destination hierarchy, which prioritises water conservation above all else:

1. Priority 1: Collected for non-potable use (rainwater harvesting)

2. Priority 2: Infiltrated to ground

3. Priority 3: Discharged to above ground surface water body

4. Priority 4: Discharged to surface water sewer

5. Priority 5: Discharged to combined sewer

This hierarchy fundamentally shifts the focus from disposal to resource management. Water is now viewed as a valuable resource to be captured and reused, not simply managed and discharged.

What This Means for Your Projects

Every development must now demonstrate why rainwater isn't being harvested before considering any other drainage solution. This isn't just about large developments—the principle applies to projects of all scales.

From our recent project experience, this is causing a complete rethink of building services design. We're seeing:

• Dual plumbing systems becoming standard

• Underground storage tanks integrated into foundation design

• Landscape irrigation systems planned from the outset

• Commercial developments incorporating harvesting into operational strategies

The Water Conservation Imperative

The new Priority 1 status for rainwater harvesting reflects the UK's growing water stress challenges. The Environment Agency's 2021 water stress classification shows that much of England faces serious water supply constraints, making conservation a national priority.

For developers, this creates both challenges and opportunities:

• Challenge: Additional system complexity and cost

• Opportunity: Reduced long-term utility costs and enhanced sustainability credentials

Planning Permission Impact

Planning authorities are now assessing applications against this hierarchy. We're seeing:

• More detailed drainage strategies required at application stage

• Specific justification needed for each hierarchy level

• Integration requirements between harvesting and building design

• Long-term management strategies becoming mandatory

Regional Implementation Variations

While the hierarchy is national, implementation varies by region:

• Water-stressed areas: Stricter harvesting requirements

• Urban areas: Focus on combined system benefits

• Rural areas: Emphasis on agricultural water reuse

• Coastal regions: Integration with flood risk management

Timeline and Cost Implications

The new standards are adding 2-4 weeks to design programmes and increasing drainage design costs by 20-40%. However, projects that embrace the hierarchy from concept stage are achieving faster approvals than those trying to retrofit compliance.

• Residential: £1,500-£3,000 per unit for harvesting systems

• Commercial: £20-£35 per m² for integrated systems

• Infrastructure: 15-25% increase in overall drainage costs

The Compliance Reality

Full compliance isn't optional—it's becoming a prerequisite for planning approval. Water companies are requiring detailed hierarchy assessments before providing connection agreements, and planning authorities are rejecting applications that don't demonstrate proper consideration of all hierarchy levels.

Future-Proofing Your Approach

The standards will become more stringent, not less. Early adoption positions your projects ahead of regulatory changes and demonstrates environmental leadership to planning authorities and end users.

Key success factors we're seeing:

• Early specialist engagement (concept stage, not detailed design)

• Integrated design approach (drainage informing architecture, not responding to it)

• Comprehensive hierarchy assessment with robust justification

• Long-term management planning from project outset

The message is clear: sustainable drainage isn't just about managing water—it's about conserving and reusing this precious resource. Projects that embrace this philosophy are not only achieving compliance but creating more resilient, valuable developments.