NSF has been testing and certifying drinking water system components for more than 70 years. The certification process is organized and follows a seven-step process that is applied across a wide range of products, including valves, flanges, and other piping components. While the overall sequence remains consistent, the specific activities performed during each step vary depending on the product being evaluated. This guide outlines the complete certification process for stainless steel flanges to NSF/ANSI/CAN 61.
The Seven Steps of NSF Certification
Step | Name | What Happens for a Flange |
1 | Application | The manufacturer applies, identifying the specific flange series, size range, and material grade |
2 | Submission | Alloy composition, manufacturing method, and any gasket or seal materials in the assembly are disclosed in full |
3 | Review | NSF’s technical team reviews the formulation and parts list line by line, confirming alloy grades and identifying what needs testing |
4 | On-Site Audit | An auditor visits the actual foundry, forge, or machine shop and collects or requests representative samples |
5 | Testing | Samples undergo laboratory extraction testing, simulating drinking-water contact under controlled conditions |
6 | Technical Evaluation | Review findings, audit results, and lab data are combined into a single pass/fail determination |
7 | Certification | The NSF mark is granted if the product passes and then maintained annually through continued audits, not a one-time approval |
NSF Certification for Flanges
Step 1: Application
The certification process begins when the manufacturer submits a formal application to NSF for evaluation. The application must clearly identify the specific flange product line seeking certification, including the flange type, size range, and stainless steel material grade. Rather than certifying a broad product category, NSF evaluates defined product families with documented specifications and manufacturing controls.
Step 2: Submission
Once the application has been accepted, the manufacturer submits the detailed technical information required for NSF’s evaluation. NSF describes this stage as the review of product formulation, toxicology, and product-use information. For stainless steel flanges, this typically includes the alloy composition, manufacturing method (such as casting, forging, or machining from plate material), coatings (if applicable), or surface treatments, and the intended drinking water application.
The manufacturer must also disclose any non-metallic materials associated with the assembly, including gaskets, seals, liners, or other wetted components. Although the flange body itself may be stainless steel, these additional materials are evaluated separately because they can introduce contaminants into drinking water. This disclosure is particularly important because fluoropolymer-based gaskets or seals can trigger additional PFAS testing and evaluation.
Step 3: Review
During the review stage, NSF’s technical team evaluates the submitted materials, product specifications, and component disclosures in detail. The review is conducted line by line to verify that all materials, formulations, and manufacturing information are complete and consistent with the product being submitted for certification. For a stainless steel flange product line, this includes confirming that the declared alloy grades, such as 304/304L or 316/316L stainless steel, match the supporting material specifications and documentation. A key objective of this stage is determining which materials and components require laboratory testing.
Step 4: On-Site Audit
After the document review is completed, NSF conducts an on-site audit of the manufacturing facility (foundry, forging operation, machine shop, or other production location). The auditor collects or requests samples directly from the line for laboratory testing to confirm the parts being produced match the products described in the application and submission stages, rather than relying solely on catalog specifications or marketing claims. A self-declared compliance claim skips this step entirely, which is why NSF treats certification and compliance as different things.
Step 5: Testing
Once the audit is complete, representative flange samples are sent to the laboratory for testing in accordance with NSF/ANSI/CAN 61 requirements. The primary evaluation is extraction testing, which simulates contact between the product and drinking water under controlled conditions designed to reflect real-world service. The water is then analyzed to determine whether any substances have leached from the product. These results are compared against the contaminant limits established by the standard and applicable toxicological criteria.
Step 6: Technical Evaluation
After testing is completed, NSF performs a comprehensive technical evaluation of the product. During this stage, the certification team consolidates the findings from the document review, manufacturing audit, and laboratory testing to determine whether the product satisfies all applicable requirements of NSF/ANSI/CAN 61. For stainless steel flanges, this evaluation goes beyond reviewing individual test results in isolation. NSF assesses the product as a complete system, confirming that the materials, manufacturing processes, audited production practices, and extraction test data collectively demonstrate compliance with the standard.
Step 7: Certification
Once NSF completes its technical evaluation and confirms that all applicable requirements have been met, certification is granted. The approved flange product line is then listed as certified and becomes eligible to bear the NSF certification mark, demonstrating compliance with NSF/ANSI/CAN 61 for drinking water system components. Certification is not a one-time approval. Instead, NSF certification is maintained through ongoing audits and surveillance activities that verify continued compliance with certification requirements. As a result, certification remains an active obligation rather than a permanent sign-off, requiring manufacturers to consistently demonstrate that their products, materials, and manufacturing processes continue to meet the standard. We cover what that ongoing obligation involves in How NSF Certification Is Earned.
What Manufacturers Need to Prepare for NSF Certification
The process moves faster when the paperwork is already in order. For flanges specifically, that generally means:
- Alloy composition and grade documentation for every material in the line, matched against current Mill Test Reports
- A clear parts list broken out by size, class, and facing type, not a single blanket description covering an entire product family
- Documentation of the manufacturing method, forged, cast, or cut from plate, since this affects what the on-site audit verifies
- Any gasket, seal, or non-metallic component specs, submitted alongside the metal body rather than treated as a separate, unrelated item
What Affects the NSF Certification Timeline?
The timeline for NSF/ANSI/CAN 61 certification depends largely on the completeness of the manufacturer’s submission and the amount of testing required for the product under review. Product complexity, the number of materials involved, and the scope of laboratory evaluation can all influence how quickly a project progresses. Although certification timelines vary, the process itself remains consistent. Every product moves through the same seven-step sequence: application, submission, review, on-site audit, testing, technical evaluation, and certification. Manufacturers that provide complete, accurate, and well-organized documentation at the outset are typically able to move through the process more efficiently, while incomplete or inconsistent submissions are among the most common causes of delays.
Conclusion
The seven-step NSF certification process follows the same framework used for a wide range of drinking water system components, but successful certification of a stainless steel flange depends on a specific set of deliverables. These include accurate material documentation, a complete and traceable parts list, manufacturing processes that match the submitted specifications, and laboratory test results that demonstrate compliance with the contaminant limits established by NSF/ANSI/CAN 61. The result is a certification program that provides manufacturers, engineers, contractors, and water utilities with confidence that products intended for drinking water service meet established public health requirements.
Every flange in API International’s CleanLine product line follows these steps. Explore our online product catalog for a comprehensive range of flanges, or contact us for custom machining in nonstandard sizes and configurations. Get connected with a dedicated sales representative today, or call us at 503.692.3800.
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Frequently Asked Questions
Does every size and grade in a flange line need separate testing?
Typically each distinct material grade and configuration is evaluated, though NSF’s technical review determines which items can be grouped versus which require individual testing.
What happens during the on-site audit specifically?
An auditor visits the actual manufacturing facility, confirms production matches what was disclosed in the submission, and collects or requests representative samples directly from the line.
Is certification a one-time approval?
No. NSF certification is granted and then maintained annually, with the facility remaining subject to ongoing audits and surveillance rather than a single sign-off.
What’s the most common reason certification takes longer than expected?
Incomplete or inconsistent documentation at the submission stage, particularly around material grades and parts lists, is the most common cause of delay.