Key Updates to the 2025 RD-1 Standard

Reorganized Structure for Clarity

One of the most noticeable updates in the 2025 RD-1 revision is the restructuring of the “Test Method” section. Previously located within Section 5, this content now stands on its own as Section 6, enabling users to more easily locate and apply testing procedures. Additionally, minor grammatical improvements and reorganized content throughout the document contribute to clearer communication and streamlined usability.

Evolution in Testing Requirements

The 2025 revision introduces new alternative testing configurations designed to complement the existing 10-foot water column test. Users now have the option to perform tests with air pressure in conjunction with water, supported by clear diagrams. This hybrid testing method offers greater flexibility, accommodating the needs of diverse testing environments and adapting to modern requirements.

Expanded Flow Requirement Standards

Flow requirement standards have been updated to incorporate recommendations from the ASPE/IAPMO/ANSI Z1034-2015 testing standard. These updates are presented alongside traditional methods and historical formulas for calculating flow capacity. By including more comprehensive testing frameworks, the 2025 RD-1 better supports a wide range of practical applications compared to the 2019 edition.

Enhanced Commentary for Practical Use Cases

The commentary section of the RD-1 standard has been enriched with guidance tailored to real-world scenarios. Notably, specific design considerations for strainers in balcony and plaza drains are now included, addressing systems outside the traditional rooftop drain applications. This expanded commentary ensures the standard remains relevant to a broader range of use cases.

Refined Terminology and Focused Changes

Precision in language is a hallmark of the 2025 RD-1 revision. Updates include replacing "roofing manufacturers" with the more accurate term "roof system manufacturers" to better reflect current industry roles. Additionally, subtle but impactful edits throughout the document ensure consistency with current best practices in technical writing.

Additional Considerations

The task force behind the 2025 revision, chaired by Liam Donovan of OMG, dedicated significant focus to nuances such as testing variability, rainfall rate data, and the separation of design considerations and backflow seal testing standards into distinct documents. These deliberate updates aim to address user feedback and industry requirements while providing greater organizational clarity.

A New Standard for Consistency and Adaptability

The 2025 RD-1 revision represents a significant step forward in establishing clearer, more adaptable, and practically applicable standards for retrofit drains. By incorporating user-centric updates and aligning with contemporary needs, the revised document sets a stronger foundation for ensuring consistent performance and compliance across the industry.