New NFPA / UL / International Standards for Fire Pipe Couplings — 2025–2026 Technical Brief

This page summarizes key standard developments in 2025–2026 that affect fire-service pipe couplings, gasketed fittings, welded outlets, flexible hose fittings, and related joining systems. It's written for specifiers, manufacturers, QA/QC engineers, installers, and procurement teams who must keep product design, testing, and project submittals up to date with the latest codes and test methods. The brief covers the most relevant NFPA (code) changes that influence allowable coupling types and installation practice, UL standards and outlines affecting qualification and listing of couplings and gasketed fittings, and recent international standards (ISO) that impact flexible connections and fittings. Each section highlights what changed (or is newly available), practical implications for manufacturers and buyers, and recommended next steps.

Executive summary — what to know right now

• NFPA 13 (2025 edition) introduced several installation and component-related clarifications that change how some couplings and fittings are allowed to be used in special ceiling heights, storage, and other restrained configurations — meaning manufacturers and designers must ensure their product submittals reference the correct 2025 NFPA clauses and test evidence. 

• UL 213 (Standard for Rubber-Gasketed Fittings for Fire-Protection Service) remains the principal US test/listing standard for gasketed couplings and grooved-type fittings; manufacturers should be using the latest UL product editions and any recent revisions or outlines of investigation to document compliance. 

• ISO 6182-18:2025 and other ISO updates now provide modernized performance and test methods for flexible sprinkler hoses and fittings — important when couplings or flexible connections are used in concealed or specialty installations. 

• Additional UL outlines and companion standards (e.g., UL 213B for welded outlets and UL piping/fittings certification services) provide targeted test requirements that influence design choices for welded vs. mechanical coupling solutions. 

1. NFPA: code changes that affect coupling selection and installation (2025–2026)

1.1 NFPA 13 (2025) — installation practices and component constraints

The 2025 edition of NFPA 13 (Standard for the Installation of Sprinkler Systems) contains multiple substantive changes that, while aimed primarily at sprinkler layout and performance, also affect acceptable uses of couplings and fittings in specific scenarios:

• Ceiling height and sprinkler type restrictions: new restrictions for ceiling heights above certain thresholds and clarifications about allowable sprinkler types or K-factors influence where mechanical couplings (grooved/gasketed) vs welded/ threaded connections can be placed — particularly in systems with high structural loads or long unsupported runs. Specifiers must ensure couplings used in such areas are covered by the installation conditions now described in NFPA 13 (2025). 

• Obstructions and supplemental sprinklers: updated definitions and provisions for sprinklers under obstructions require installers to consider how couplings and branch connections affect flow and alignment; deviations in pipe geometry caused by improper coupling installation can affect hydraulic calculations and compliance. 

1.2 NFPA 25 (2026 proposals) — inspection & maintenance implications

While NFPA 25 (Inspection, Testing, and Maintenance) updates for 2026 are still in development, proposed changes emphasize component traceability, inspection intervals, and documented maintenance for mechanical fittings and couplings. This increases demand for manufacturer documentation (installation instructions, torque specs, gasket materials, and deterioration acceptance criteria) to be provided with listed couplings. 

Practical implication: Designers and owners should require that coupling submittals explicitly reference the edition of NFPA 13/25 used for hydraulic calculations and demonstrate that couplings will not compromise the required clearances, flow, or support requirements introduced in the 2025–2026 code cycle.

2. UL standards and outlines — what changed for couplings and fittings

2.1 UL 213 — Rubber-Gasketed Fittings for Fire-Protection Service

UL 213 is the primary standard used in the US to evaluate rubber-gasketed couplings and fittings (grooved couplings, flexible couplings, side outlets). The standard’s scope covers couplings used to assemble run pipe, provide branch outlets, and permit limited deflection — so certification to UL 213 remains essential for most mechanical coupling products intended for use in NFPA-compliant systems. Manufacturers should confirm they are referencing the latest UL edition or product listing (UL updates and revisions can contain new test procedures or marking requirements). 

2.2 UL outlines & companion documents (UL 213B, product certification services)

• UL 213B (Outline for Welded Outlets, Ed. 6, 2022) and similar outlines define testing for welded outlet fittings that connect to steel pipe. These documents are essential when choosing welded vs. mechanical outlet strategies and provide the test basis for structural strength and bending moment resistance. Use the current outline when preparing submittals for welded outlet designs. 

• UL Solutions — Pipes & Fittings testing/certification pages provide guidance on scope, test types (hydrostatic, cyclic, mechanical), and listing processes that manufacturers can use to ensure the coupling product will be accepted by authorities having jurisdiction (AHJs). 

Practical implication: If a coupling design has been modified (materials, gasket compound, geometry), UL listing must be updated or reconfirmed under the current edition/outlines. Builders and specifiers should request current UL listing numbers and test reports as part of procurement.

3. International standards (ISO / EN) — flexible connections and fittings

3.1 ISO 6182-18:2025 — flexible sprinkler hoses with fittings

ISO 6182-18:2025 is a newly available ISO document covering flexible sprinkler hoses and their fittings — it sets performance, marking requirements and test methods for flexible attachments to sprinklers. When couplings are used as part of flexible hose assemblies (e.g., to bridge movement or for difficult routing), manufacturers and specifiers must ensure hose + coupling assemblies meet this ISO standard (or an equivalent national standard). 

3.2 EN standards and regional convergence

Several EN standards and regional test frameworks also influence couplings sold in Europe and other markets. Where a single project spans multiple jurisdictions, compliance to both UL/FM and relevant ISO/EN standards (and proof of equivalence) will simplify approvals.

Practical implication: Exporters and multi-market suppliers should maintain dual test evidence (UL/FM + ISO/EN) where feasible — particularly for flexible connection assemblies, which are now explicitly covered in ISO 6182-18:2025.

4. Key technical trends and how standards reflect them

1. Higher expectation of documentation & traceability: NFPA proposals and UL certification practice both push manufacturers to publish clear installation, maintenance, and material traceability documentation for couplings.

2. Focus on flexible connections: ISO 6182-18:2025 acknowledges the widespread use of flexible hoses and fittings, standardizing test methods so that assemblies with couplings are assessed consistently. 

3. Compatibility with chrome-free pretreatments and modern materials: As the market shifts to chromium-free pretreatment and new gasket elastomers, UL/ISO testing protocols increasingly require materials data and aging test results. 

5. What manufacturers, specifiers and purchasers should do now (action checklist)

• Update spec language: call out the edition of NFPA (2025) and UL standards (state UL 213 and any relevant UL outlines) required for project compliance. Require test reports and listing numbers in the bid package. 

• Request full listing evidence: ask suppliers for current UL listing numbers, the exact UL edition or outline used for testing, and copies of representative test reports (hydrostatic, bending moment, cyclic fatigue, gasket aging). 

• For flexible assemblies: require ISO 6182-18:2025 compliance (or acceptable national equivalent) for hose + coupling subassemblies. 

• Confirm installation compatibility with NFPA 13 (2025): ensure hydraulic calculations, support spacing, and allowable fittings are validated against the 2025 clauses for high ceilings, obstructions, and special occupancies. 

• Plan for maintenance documentation: include coupling inspection criteria and replacement intervals in O&M manuals aligned with NFPA 25 updates. 

6. Typical questions & short answers

• Q: Does UL 213 still cover grooved couplings?
  A: Yes — UL 213 remains the primary standard for rubber-gasketed fittings (grooved/gasket couplings) in fire protection, and manufacturers should reference the latest UL edition/listing. 

• Q: Do I need ISO 6182-18 for all flexible hoses used in sprinkler systems?
  A: If you specify or purchase flexible sprinkler hose assemblies, ISO 6182-18:2025 provides the up-to-date, internationally recognized performance & marking requirements; require it for assemblies to ensure consistent performance. 

• Q: Will NFPA 13 (2025) ban certain coupling types?
  A: NFPA 13 (2025) clarifies and restricts some installation conditions (e.g., high ceilings, specific sprinkler types) that may limit where certain coupling types are acceptable unless the coupling is demonstrated to meet the mechanical and hydraulic requirements. It does not categorically ban coupling types but raises the bar for documented suitability.

References (selected sources)

1. Key changes proposed for the 2025 edition of NFPA 13 — NFPA technical blog. 

2. NFPA 13 — Standard development and edition information — NFPA codes & standards pages. 

3. UL 213 | Standard for Rubber-Gasketed Fittings for Fire-Protection Service — UL Standards product page / shop.

4. ISO 6182-18:2025 — Fire protection — Automatic sprinkler system (flexible sprinkler hose with fittings) — ISO catalogue. 

5. UL Solutions — Fire sprinkler pipe and fittings testing and certification — UL Solutions service page.

6. UL 213B Ed. 6 (Outline of Investigation for Welded Outlet Fittings) — ANSI/UL store summary.