New SuDS Standards for Architects: What You Need to Know in 2025

As sustainable drainage systems (SuDS) continue to evolve, architects across the UK are facing updated standards and requirements that significantly impact project planning and design. At The Drainage Designers, we've been closely monitoring these changes to help our architect partners navigate the new landscape effectively.

Understanding the Updated SuDS Framework

The latest SuDS standards represent a shift towards more stringent environmental protection and flood risk management. These changes aren't just regulatory updates - they're fundamental improvements to how we approach sustainable water management in development projects.

The New Hierarchy: Rainwater Harvesting Takes Priority

Critical Change: Rainwater Harvesting First One of the most significant updates to the SuDS standards is the new requirement to prioritise rainwater harvesting above infiltration methods. This represents a fundamental shift in the drainage hierarchy that architects must understand and implement from the earliest design stages.

Previously, the focus was primarily on managing surface water through infiltration and attenuation. Now, architects must first consider how rainwater can be captured, stored, and reused before exploring other drainage solutions.

Key Changes Affecting Architectural Design

Enhanced Planning Requirements Local authorities are now requiring more detailed SuDS proposals at the planning stage, with specific emphasis on rainwater harvesting systems. Gone are the days when a basic drainage statement would suffice. Architects must now demonstrate comprehensive understanding of water reuse potential from the earliest design phases.

Rainwater Harvesting Integration The new standards require architects to think beyond simple water collection. This isn't just about installing water butts in gardens—it's about comprehensive rainwater reuse systems that can serve:

• Toilet flushing

• Shower and bath water (with appropriate treatment)

• Washing machine supply

• Garden irrigation

• Commercial cleaning applications

Stricter Discharge Rate Controls The updated standards impose tighter restrictions on surface water discharge rates, often requiring developments to achieve discharge rates significantly below pre-development levels. However, effective rainwater harvesting can significantly reduce the volume requiring discharge, making compliance more achievable.

Improved Integration Standards The updated guidance emphasises the integration of rainwater harvesting systems into the overall architectural design. This means considering:

• Tank locations and access requirements

• Pump and filtration system housing

• Distribution pipework routes

• Control system integration

• Maintenance access provisions

Rainwater Harvesting: Beyond Water Butts

Comprehensive System Design Modern rainwater harvesting requires sophisticated system design that architects must accommodate:

Collection Systems

• Roof catchment area calculations

• Gutter and downpipe sizing

• First-flush diverters

• Leaf screens and filters

Storage Solutions

• Underground tank positioning

• Above-ground tank integration

• Pump chamber design

• Overflow management

Distribution Systems

• Dual plumbing systems for potable and non-potable water

• Pump and pressure vessel housing

• Control panel locations

• Monitoring system integration

Treatment Considerations For applications beyond toilet flushing and irrigation, architects must consider:

• Filtration system space requirements

• UV sterilisation equipment

• Water quality monitoring systems

• Backflow prevention measures

Why Early Consultation Matters More Than Ever

With rainwater harvesting now taking priority in the SuDS hierarchy, early consultation has become absolutely critical. Here's why timing is crucial:

System Integration Complexity Rainwater harvesting systems require coordination with:

• Structural design (tank foundations and loadings)

• Electrical services (pumps and controls)

• Plumbing design (dual water systems)

• Landscape design (overflow management)

Space Planning Requirements Effective rainwater harvesting systems require significant space allocation:

• Storage tanks (typically 1m³ per 50m² of roof area)

• Plant rooms for pumps and controls

• Access routes for maintenance

• Distribution pipework routes

Planning Approval Success Our experience shows that projects incorporating comprehensive rainwater harvesting from the design stage achieve higher approval rates and fewer conditional requirements.

Practical Implications for Architects

Space Allocation for Rainwater Harvesting

Modern standards require careful consideration of space allocation for:

• Primary storage tanks (underground or integrated into structure)

• Secondary treatment systems

• Pump and control equipment

• Distribution pipework (separate from potable water systems)

• Access routes for maintenance and monitoring

Design Coordination Requirements

Successful rainwater harvesting implementation requires:

• Early structural engineer involvement (tank loadings and foundations)

• Mechanical and electrical coordination (pumps, controls, monitoring)

• Plumbing system design (dual water supply networks)

• Landscape integration (overflow management and aesthetics)

Technology Integration

Architects should specify rainwater harvesting technologies that:

• Meet current water quality standards for intended use

• Integrate seamlessly with building services

• Provide reliable operation with minimal maintenance

• Include monitoring and control systems

Common Challenges and Solutions

Challenge: Limited Site Space Urban developments often lack space for traditional rainwater harvesting systems.

Solution: Innovative Integration Approaches

• Structural integration of storage tanks

• Multi-functional basement spaces

• Modular above-ground systems with architectural screening

• Integration with landscape features

Challenge: Dual Plumbing Systems Separate distribution systems for harvested rainwater increase complexity and cost.

Solution: Strategic System Design

• Focus on high-volume, low-quality applications (toilets, washing machines)

• Centralised plant rooms for efficient distribution

• Clear labelling and colour-coding systems

• Integration with building management systems

Challenge: Maintenance and Monitoring Rainwater harvesting systems require ongoing maintenance and water quality monitoring.

Solution: Accessible Design

• Design clear access routes to all system components

• Specify monitoring systems with remote capability

• Provide adequate space for maintenance equipment

• Consider maintenance contracts from design stage

Best Practices for Architects

1. Prioritise Rainwater Harvesting: Always consider rainwater reuse before infiltration or attenuation

2. Engage Early: Involve drainage and water system specialists during concept design

3. Plan for Dual Systems: Design buildings to accommodate separate potable and non-potable water systems

4. Allocate Adequately: Reserve sufficient space for tanks, plant, and access routes

5. Consider Maintenance: Design systems that can be maintained efficiently

6. Integrate Aesthetically: View rainwater harvesting as a design feature, not just infrastructure

7. Stay Updated: Regulations continue to evolve—maintain awareness of local authority requirements

Working with The Drainage Designers

Our approach to supporting architects with the new rainwater harvesting requirements includes:

• Early Design Consultation: We review architectural proposals and provide rainwater harvesting feasibility advice

• System Integration: We work collaboratively to integrate harvesting systems with architectural vision

• Regulatory Expertise: We maintain current knowledge of rainwater harvesting standards across England and Scotland

• Comprehensive Design: We consider the complete water cycle, from collection to reuse and overflow management

Looking Ahead

The prioritisation of rainwater harvesting represents a fundamental shift in how we approach water management in buildings. This isn't just about compliance - it's about creating more sustainable, resilient developments that reduce demand on mains water supplies and minimise surface water discharge.

Successful architectural practices are already adapting by:

• Building rainwater harvesting expertise within their teams

• Establishing relationships with water system specialists

• Incorporating dual water systems into standard design processes

• Viewing water reuse as both environmental responsibility and design opportunity

Conclusion

The new SuDS standards, with their emphasis on rainwater harvesting as the first priority, represent both challenges and opportunities for architects. While system complexity has increased, these requirements also provide opportunities to create more sustainable, self-sufficient developments.

At The Drainage Designers, we're committed to helping architects navigate these changes successfully. Our experience with over 40 years in drainage design, combined with our understanding of current regulatory requirements and rainwater harvesting systems, ensures your projects meet the highest standards while achieving planning approval efficiently.