If you're writing an RFQ for butterfly valves, one of the first questions is: which standard should I specify — API 609 or AWWA C504?
Both are widely used butterfly valve standards, but they serve different worlds. API 609 is the oil & gas and industrial standard. AWWA C504 is the water utility standard. Choosing the wrong one means either over-specifying (paying for metal seats you don't need) or under-specifying (getting a valve that won't pass inspection).
This guide explains both standards in plain English, the key differences, and how to choose for your project.
What Is API 609?
API 609 (American Petroleum Institute) covers butterfly valves for oil, gas, chemical and general industrial service. It defines:
- Types: Concentric (rubber-seated), double offset and triple offset valves
- Pressure classes: up to Class 600 (PN100), including higher-pressure metal-seated designs
- Sizes: typically NPS 2 to NPS 48 (DN50 to DN1200) in standard coverage
- Testing: shell and seat tests per API 598, with leakage classes from Class VI (soft) down to Class V and tighter for metal seats
- Design requirements: stem retention, torque calculations, fire-safe options (API 607)
When buyers specify API 609, they typically need documentation, material traceability and either soft-seat or metal-seat performance for process service.
What Is AWWA C504?
AWWA C504 (American Water Works Association) covers rubber-seated butterfly valves for water supply and wastewater service. It defines:
- Type: Concentric, rubber-seated valves (the standard explicitly covers this design)
- Pressure classes: 150B, 250B and 250A (roughly PN10 to PN25)
- Sizes: 3" to 72" (DN80 to DN1800), with most water utilities specifying through 48"
- Design requirements: body and disc thickness, seat retention, operator torque requirements, and closure/opening limits
- Testing: shell, seat and hydrostatic tests per the standard's own requirements
AWWA C504 is the go-to for drinking water plants, wastewater treatment and irrigation because it is written around what water utilities actually need: dependable rubber-seated valves with predictable operating torque.
Key Differences at a Glance
| Aspect | API 609 | AWWA C504 |
|---|---|---|
| Primary service | Oil & gas, chemical, industrial | Water supply, wastewater |
| Valve types | Concentric, double offset, triple offset | Concentric rubber-seated |
| Pressure | Up to Class 600 (PN100) | 150B / 250B / 250A (PN10–PN25) |
| Size range | NPS 2–48 typical | 3"–72" |
| Seat options | Rubber, PTFE, metal | Rubber (EPDM/NBR) |
| Testing | API 598, leakage classes V–VI | Standard's own hydrostatic/seat tests |
| Operator focus | Process control, fire safety | Predictable torque, utility reliability |
Which Standard Should You Specify?
Choose AWWA C504 when…
- Your service is water, wastewater or irrigation
- You need rubber-seated valves up to PN25
- A water utility or municipality is the end client (they often require it)
- You want the standard's torque and operator sizing guidance
Choose API 609 when…
- Your service is oil & gas, chemical or industrial
- You need higher pressure ratings (beyond PN25) or metal seats
- Fire-safe or tight metal shutoff is required (double/triple offset)
- The project spec or EPC requires API compliance
Can one valve meet both?
Yes, in many cases. A rubber-seated concentric wafer or lug butterfly valve in Class 150B/250B can be designed to satisfy both AWWA C504 and API 609 requirements where they overlap — sizes, pressure, and testing. If your project might be inspected under either standard, ask your supplier for a dual-compliance statement in the quotation.
What to Put in Your RFQ
To avoid confusion and rework, include these in every butterfly valve RFQ:
- Governing standard — API 609 or AWWA C504 (or both, with primary marked)
- Size and pressure class — e.g. DN200, Class 250B / PN16
- End connection — wafer, lug or flanged
- Body and disc material — ductile iron, carbon steel or stainless steel
- Seat material — EPDM, NBR, PTFE or metal
- Testing and documentation — shell/seat test reports, material certificates (EN 10204 / SGS)
How Reguvale Can Help
We manufacture wafer, lug and flanged butterfly valves in DN50–DN1200, in ductile iron, carbon steel and stainless steel, with EPDM, NBR, PTFE and metal seats. Valves ship with ISO 9001 and SGS material test certificates, and we can provide dual API 609 / AWWA C504 compliance statements where applicable.
Ready stock on standard sizes — ship within 5–7 days. Send us your RFQ and we’ll confirm the right standard and specification for your project.