How to Identify and Measure Fittings
Pipe size is an industry designation, not the actual size. View information about how to measure threaded and unthreaded pipe and pipe fittings.
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Low-Pressure Iron and Steel Threaded Pipe Fittings
Use these fittings for low-pressure applications in noncorrosive environments.
Compact straight connectors are able to fit into tight spaces. They are also known as merchant couplings. Connectors with NPSC threads are fully threaded from one end. Connectors with NPT threads are threaded on both ends.
NPTF (Dryseal) threads, NPSC (National Pipe Straight Coupling) threads, and NPSL (National Pipe Straight Locknut) threads are compatible with NPT threads.
For technical drawings and 3-D models, click on a part number.

- For Use With: Air, Steam, Oil, Water, Natural Gas
- Pressure Class: 150
- Specifications Met: ASTM A53, ASTM A865
- Pipe Nipples and Pipe: Use Schedule 40 steel
Pipe Size | Max. Pressure | Max. Steam Pressure | Material | Each | |
NPSC Female—Fully Threaded from One End | |||||
---|---|---|---|---|---|
1/8 | 150 psi @ 72° F | 150 psi @ 350° F | Steel | 000000000 | 00000 |
1/4 | 150 psi @ 72° F | 150 psi @ 350° F | Steel | 000000000 | 0000 |
3/8 | 150 psi @ 72° F | 150 psi @ 350° F | Steel | 000000000 | 0000 |
1/2 | 150 psi @ 72° F | 150 psi @ 350° F | Steel | 000000000 | 0000 |
3/4 | 150 psi @ 72° F | 150 psi @ 350° F | Steel | 000000000 | 0000 |
1 | 150 psi @ 72° F | 150 psi @ 350° F | Steel | 000000000 | 0000 |
1 1/4 | 150 psi @ 72° F | 150 psi @ 350° F | Steel | 000000000 | 00000 |
1 1/2 | 150 psi @ 72° F | 150 psi @ 350° F | Steel | 000000000 | 00000 |
2 | 150 psi @ 72° F | 150 psi @ 350° F | Steel | 000000000 | 00000 |
NPT Female—Threaded on Both Ends | |||||
2 1/2 | 150 psi @ 72° F | 150 psi @ 350° F | Steel | 000000000 | 00000 |
3 | 150 psi @ 72° F | 150 psi @ 350° F | Steel | 000000000 | 00000 |
4 | 150 psi @ 72° F | 150 psi @ 350° F | Steel | 000000000 | 000000 |
Low-Pressure Galvanized Iron and Steel Threaded Pipe Fittings
The galvanized finish on these fittings provides fair corrosion resistance. Fittings are for use in low-pressure applications.
Compact straight connectors are able to fit into tight spaces. They are also known as merchant couplings. Connectors with NPSC threads are fully threaded from one end. Connectors with NPT threads are threaded on both ends.
NPSC (National Pipe Straight Coupling) threads and NPSL (National Pipe Straight Locknut) threads are compatible with NPT threads.
For technical drawings and 3-D models, click on a part number.

- For Use With: Air, Steam, Oil, Water, Natural Gas
- Pressure Class: 150
- Specifications Met: ASTM A53, ASTM A865, ASTM B633
- Pipe Nipples and Pipe: Use Schedule 40 galvanized steel
- Flanges: Use Class 150 galvanized steel
Pipe Size | Max. Pressure | Max. Steam Pressure | Material | Each | |
NPSC Female—Fully Threaded from One End | |||||
---|---|---|---|---|---|
1/8 | 150 psi @ 72° F | 150 psi @ 350° F | Galvanized Steel | 000000000 | 00000 |
1/4 | 150 psi @ 72° F | 150 psi @ 350° F | Galvanized Steel | 000000000 | 0000 |
3/8 | 150 psi @ 72° F | 150 psi @ 350° F | Galvanized Steel | 000000000 | 0000 |
1/2 | 150 psi @ 72° F | 150 psi @ 350° F | Galvanized Steel | 000000000 | 0000 |
3/4 | 150 psi @ 72° F | 150 psi @ 350° F | Galvanized Steel | 000000000 | 0000 |
1 | 150 psi @ 72° F | 150 psi @ 350° F | Galvanized Steel | 000000000 | 00000 |
1 1/4 | 150 psi @ 72° F | 150 psi @ 350° F | Galvanized Steel | 000000000 | 00000 |
1 1/2 | 150 psi @ 72° F | 150 psi @ 350° F | Galvanized Steel | 000000000 | 00000 |
2 | 150 psi @ 72° F | 150 psi @ 350° F | Galvanized Steel | 000000000 | 00000 |
NPT Female—Threaded on Both Ends | |||||
2 1/2 | 150 psi @ 72° F | 150 psi @ 350° F | Galvanized Steel | 000000000 | 00000 |
3 | 150 psi @ 72° F | 150 psi @ 350° F | Galvanized Steel | 000000000 | 00000 |
4 | 150 psi @ 72° F | 150 psi @ 350° F | Galvanized Steel | 000000000 | 000000 |
Low-Pressure Aluminum Threaded Pipe Fittings
In addition to being lightweight, these aluminum fittings offer good corrosion resistance. Use them in low-pressure flow applications. To prevent cracking, do not tighten more than a 1/4-turn past hand tight.
Threaded female x butt weld straight adapters are also known as half couplings.
For technical drawings and 3-D models, click on a part number.

- For Use With: Air, Oil, Water
- Specifications Met: See table
- Pressure Class: 150
- Pipe Nipples and Pipe: Use Schedule 40 aluminum
- Flanges: Use Class 125 aluminum
Pipe Size | Max. Pressure | Specifications Met | Each | |
NPT Female × Butt Weld | ||||
---|---|---|---|---|
3/8 | 150 psi @ 72° F | ASME B1.20.1, ASTM A865, ASTM B221 | 000000000 | 00000 |
1/2 | 150 psi @ 72° F | ASME B1.20.1, ASTM A865, ASTM B221 | 000000000 | 0000 |
1 1/4 | 150 psi @ 72° F | ASME B1.20.1, ASTM A865, ASTM B221 | 000000000 | 0000 |
1 1/2 | 150 psi @ 72° F | ASME B1.20.1, ASTM A865, ASTM B221 | 000000000 | 0000 |
2 | 150 psi @ 72° F | ASME B1.20.1, ASTM A865, ASTM B221 | 000000000 | 00000 |
4 | 150 psi @ 72° F | ASME B1.20.1, ASTM A865, ASTM B221 | 000000000 | 00000 |
6 | 150 psi @ 72° F | ASME B1.20.1, ASTM A865, ASTM B221 | 000000000 | 000000 |