2-1/2-8 NPT vs 3-8NPSH: specs compared
Updated 05 September 2026.
88.14 mm
3-8NPSH wins on major diameter
On major diameter, 3-8NPSH leads: 88.14 mm versus 73.02 mm.
| Spec | 2-1/2-8 NPT | 3-8NPSH |
|---|---|---|
| Designation | 2-1/2-8 NPT | 3-8NPSH |
| Major diameter | 73.02 mm | 88.14 mm |
| Threads per inch / pitch | 8 | 8 |
| Thread form | tapered, 60 degree | straight (parallel), 60 degree |
| Seals on | on the thread flanks with PTFE tape | gasket in the coupling |
Questions and answers
Which has the higher major diameter, 2-1/2-8 NPT or 3-8NPSH?
On major diameter, 3-8NPSH leads: 88.14 mm versus 73.02 mm.
How do 2-1/2-8 NPT and 3-8NPSH compare?
On major diameter, 3-8NPSH leads: 88.14 mm versus 73.02 mm.