How to Specify a Brass Fitting: A Checklist for Engineers

I review a lot of purchase orders. And I can tell you with confidence that at least half of the problems we encounter in order fulfilment — wrong product delivered, specification dispute, customer dissatisfaction — trace back to an incomplete or ambiguous specification provided at the time of order.

This is not a criticism of the buyers who write these orders. It's a reflection of how complex a full fitting specification actually is when you list all the variables — and how many of those variables are left implicit or assumed when they shouldn't be. This checklist is my attempt to prevent those problems by making explicit everything that needs to be specified.

The Complete Specification Checklist

1. Fitting Type and Function

What type of fitting is it? Ball valve. Compression tee. Forged elbow. Needle valve. Non-return valve. Manifold. Be specific — "elbow" without further detail could mean a straight threaded elbow, a compression elbow, a push-fit elbow, a flared elbow, or others. The function (isolation, direction change, branch, regulation, non-return) should also be stated to confirm the correct product type is selected.

2. End Connections

For every end connection on the fitting, specify:

• Connection type: Threaded / Compression / Push-fit / Solder / Flanged / Press-fit
• If threaded: Thread standard (BSPP / BSPT / NPT) + nominal size + male or female
• If compression: Tube OD in mm or inches + tube material (copper / stainless / plastic)
• If flanged: Flange standard (PN / ANSI class) + flange face type (RF / FF / RTJ)

3. Material Specification

Body: Specify the alloy grade explicitly — CW617N for standard, CW602N for DZR, CW614N for machined parts, bismuth grade for lead-free. "Brass" alone is not sufficient.

Sealing elements: PTFE seats (for ball valves), NBR or EPDM O-rings (for pressure ratings and chemical compatibility), graphite packing (for high temperature). Specify material, not just "standard seals."

4. Pressure and Temperature Rating

State the required pressure rating at the maximum operating temperature. Not just "PN25" — "PN25 at 100°C operating temperature." If the system sees pressure transients (water hammer, pump surge), state the transient pressure as well.

5. Size (Nominal and Physical)

Nominal pipe size (DN / NPS / inch nominal) for threaded connections. Tube OD for compression connections. Body to body or face to face dimension for critical envelope constraints. Weight per unit if relevant to logistics or structural calculation.

6. Applicable Standards

List the standards the fitting must comply with: EN 13828, EN 1254-1, BS EN 331, WRAS, WaterMark, NSF/ANSI 61, ISO 9001 manufacturing, etc. These drive both the design requirements and the required documentation you'll receive with the product.

7. Required Certifications and Documentation

Be specific about what documentation you need to accompany delivery:

• Material certificate (with lot number and chemical composition)
• Hydrostatic pressure test certificate (batch-specific)
• Thread gauging certificate
• WRAS approval reference (if required)
• Declaration of Conformity for CE marking
• Third-party inspection report (if pre-shipment inspection is required)

8. Special Requirements

Does the fitting need a locking handle? Anti-static provision (gas applications)? Specific temperature marking? Extended stem for insulated pipework? Anti-tamper feature? These are not standard — they must be specified explicitly.

9. Quantity and Packaging

Total quantity. Packing: individual polybag? Bulk in carton? Specific labelling on outer carton? Country of origin marking requirement? These affect both manufacturing planning and shipping cost.

10. Quality Level (AQL)

For large orders, specify the acceptance quality level for incoming inspection: AQL 1.0 (tighter), AQL 2.5 (standard commercial), or AQL 4.0 (less stringent). This communicates to the manufacturer the quality standard you expect and to your own receiving inspection team the sampling plan to apply.

The Payoff: Why This Matters

An order placed with all ten categories specified will be fulfilled correctly the first time, with no back-and-forth clarification, no risk of receiving the wrong thread standard, and no dispute over what documentation should accompany the goods.

An order that says "500 brass ball valves, ½ inch, standard" will generate a clarification request, may be fulfilled with assumptions that turn out to be wrong, and arrives without the documentation you needed for your quality records.

Five minutes invested in a complete specification saves days of problem resolution. That trade is always worth making.