Reduce rework, delays, and mismatched parts by tightening up your fitting specs
Procurement teams and project engineers rarely get in trouble for choosing a “good” fitting—they get in trouble when the fitting isn’t compatible with the pipe schedule, pressure class, joining method, or governing standard. This guide breaks down how to specify pipe fittings across waterworks, fire protection, and industrial piping so you can buy once, install once, and keep projects moving across the United States.
Why “pipe fittings” is a high-risk line item
A fitting is small compared to the total project cost, but it can dictate whether a system passes pressure testing, flows as designed, and meets inspection. The most common failure points in purchasing are:
Mismatch of standards: Ordering a fitting built to the wrong dimensional standard or pressure rating.
Wrong end connection: Butt-weld vs. socket-weld vs. threaded vs. grooved vs. flanged vs. mechanical joint.
Wall thickness and schedule confusion: “Same NPS” does not guarantee same bore or compatibility.
Environmental/compatibility issues: Corrosion allowance, lining/coating, temperature, and chemical exposure.
For buyers supporting multiple job types (municipal water, industrial process, and fire protection), the same fitting “shape” can have completely different requirements depending on the system.
Start with the system: waterworks vs. fire protection vs. industrial
Buying the right pipe fittings becomes easier when you categorize the system first:
Waterworks & Irrigation
Often ductile iron or PVC-based networks, with a heavy emphasis on standardized dimensions, long life, and field-friendly joints (mechanical joint, push-on, flanged in some applications).
Fire Protection
Commonly steel piping with grooved, threaded, or welded connections depending on design. Consistency with listed/approved components and the job’s governing standard matters for inspection outcomes.
Industrial / PVF
Broad range of materials (carbon steel, stainless, alloys) and higher variation in pressure-temperature conditions. Spec clarity is key: material grade, schedule, end prep, NDE/testing, and documentation.
Quick “Did you know?” facts that prevent bad orders
ASME B16.9 covers overall dimensions, tolerances, ratings, testing, and markings for factory-made wrought buttwelding fittings across a wide NPS range. (asme.org)
ASME B16.5 addresses pipe flanges and flanged fittings and includes pressure-temperature ratings, dimensions, tolerances, marking, and testing (with specific class and NPS limits). (asme.org)
For municipal water, standards like AWWA C110/A21.10 cover ductile-iron and gray-iron fittings for use with ductile-iron pipe in common water service size ranges. (store.awwa.org)
For compact ductile iron fittings, AWWA C153 describes 3-in. through 64-in. compact fittings and lists minimum working pressures by size range (commonly used in water, wastewater, and reclaimed water). (store.awwa.org)
Step-by-step: How to specify pipe fittings (the checklist buyers wish they had)
1) Define service, governing standard, and acceptance expectations
Start your RFQ with what the system is doing and what it must comply with: potable water, reclaimed water, fire protection, compressed air, chemical service, etc. Add the design pressure/temperature, and the inspection or documentation requirements (material test reports, certifications, traceability).
2) Identify pipe size convention and wall thickness
Provide NPS/DN and the pipe wall standard (Schedule, DR, or pipe class depending on material). The fitting must match the pipe OD/ID assumptions for alignment, flow, and welding/grooving/thread engagement.
3) Choose the end connection that matches install reality
End connections determine labor, tools, and field risk. Common choices:
Butt-weld (often governed by ASME B16.9 for many industrial applications). (asme.org)
Flanged (ASME B16.5 is a frequent reference point for flange dimensions and classes). (asme.org)
Mechanical joint / push-on (common in waterworks networks; many specs reference AWWA standards). (store.awwa.org)
Threaded / socket-weld / grooved (common on fire protection and industrial skids; ensure compatibility with the job’s standard and installation method).
4) Specify material grade (not just “carbon steel”)
Material grade affects corrosion resistance, weldability, temperature limits, and documentation. For example, ASTM A105/A105M is a common forged carbon steel material spec for piping components used in pressure systems (including flanges, fittings, valves, and similar parts). (store.astm.org)
5) Add the “project killers”: coating/lining, pressure class, and marking
If you don’t call these out, you can end up with a technically “correct” fitting that fails your application:
Coating/lining: Fusion-bonded epoxy, cement mortar lining, galvanizing, etc., depending on service.
Pressure class/rating: Especially for flanged components—ASME B16.5 addresses class designations and pressure-temperature ratings. (asme.org)
Marking/traceability: Heat numbers, manufacturer marks, and any required stamping to support QA/QC.
At-a-glance table: What to include on a pipe fitting RFQ
| RFQ Field | Example | Why it matters |
|---|---|---|
| Service / medium | Potable water / fire sprinkler / compressed air | Drives material + coating/lining and compliance needs |
| Size & wall | NPS 4, Sch 40 (or DR / pipe class) | Prevents misalignment and end-prep mismatches |
| End connection | Butt-weld / flanged / MJ / grooved | Defines installation method, tools, and lead time |
| Dimensional standard | ASME B16.9 / ASME B16.5 / AWWA C110 / AWWA C153 | Ensures interchangeability and fit-up across vendors (asme.org) |
| Material grade | ASTM A105 forged carbon steel (example) | Controls mechanical properties, welding, and traceability (store.astm.org) |
| Documentation | MTRs, COO, inspection, packing | Critical for export and QA/QC sign-off |
Local angle: buying pipe fittings across the United States (and shipping without surprises)
For multi-site buyers supporting projects in Boise, Salt Lake City, Denver, Phoenix, Seattle, and beyond, the “best” fitting isn’t only about spec—it’s also about availability, packaging, and logistics. A few practical ways to reduce supply-chain friction:
Standardize your naming: Use a single internal line description format (size + end type + standard + material + coating).
Call out export needs early: If a shipment may cross borders, specify required paperwork and packing method up front.
Plan for field realities: Mixed inventories (threaded + grooved + flanged) drive mix-ups—labeling and kitting can prevent costly returns.
Keep critical spares aligned: If your maintenance team uses the same fitting families across sites, reorders become faster and cleaner.
IFW Supply supports buyers nationwide with fire protection, waterworks & irrigation, industrial PVF, and safety products—plus export-ready support when documentation and packing requirements matter.
Need help matching pipe fittings to your spec, lead time, and shipping plan?
IFW Supply helps procurement teams and project engineers source fire protection, waterworks & irrigation, industrial PVF, and safety products—backed by responsive quoting and export-ready support.
FAQ: Pipe fittings
What information should I include when ordering pipe fittings?
Include system/service, size, wall/schedule (or DR/class), end connection type, governing dimensional standard, material grade, coating/lining (if any), pressure class/rating (when applicable), and documentation needs (MTRs, COO, inspections, packing).
What’s the difference between ASME B16.9 and ASME B16.5?
ASME B16.9 is commonly referenced for factory-made wrought buttwelding fittings and addresses dimensions, tolerances, and related requirements. (asme.org) ASME B16.5 is focused on pipe flanges and flanged fittings and includes pressure-temperature ratings, materials, dimensions, marking, and testing. (asme.org)
For waterworks, when would I reference AWWA C110 vs. AWWA C153?
AWWA C110 is a widely used standard for ductile-iron and gray-iron fittings (commonly used with ductile-iron pipe in municipal water service ranges). (store.awwa.org) AWWA C153 covers ductile-iron compact fittings and includes size ranges and working pressure guidance commonly applied to potable water, wastewater, and reclaimed water. (store.awwa.org)
Is “ASTM A105” a fitting standard or a material standard?
ASTM A105/A105M is a material specification for forged carbon steel components used in pressure systems (including flanges, fittings, valves, and similar parts). Dimensional standards (like ASME B16.5 or ASME B16.9) still determine geometry and end-to-end dimensions. (store.astm.org)
Glossary (quick definitions for common fitting terms)
NPS (Nominal Pipe Size): A standardized pipe size designation (not a true measured OD/ID).
Schedule (Sch): A wall thickness series commonly used for steel pipe and fittings (affects ID and weight).
Butt-weld fitting: A fitting designed to be welded end-to-end with pipe (common in industrial process piping).
Flanged fitting: A fitting with bolted flanges used for removable joints; flange dimensions and ratings are standardized in common specifications such as ASME B16.5. (asme.org)
Mechanical joint (MJ): A gasketed, bolted joint style widely used in waterworks distribution networks (often referenced through AWWA standards).
MTR (Mill Test Report): A material certification document that ties chemical/mechanical properties to a heat/lot for traceability and QA/QC.