Frequently Asked Questions
The image above shows the ‘Basic Major Diameter’ of a 1½” BSP thread
How to measure BSP thread sizes
The “Basic Major Diameter (mm)” can be obtained by measuring the larger thread diameter on the threads of your immersion – typically called the “across the thread” measurement.
The “Basic Minor Diameter (mm)” can be obtained by measuring the smaller thread diameter. This measurement will closely resemble the measurement on the “port” or “inlet” on the tank.
| BSP | Basic Major Dia. (mm) | Basic Minor Dia. (mm) |
|---|---|---|
| 1/16″ | 7.72 | 6.56 |
| 1/8″ | 9.73 | 8.56 |
| 1/4″ | 13.16 | 11.45 |
| 3/8″ | 16.66 | 14.95 |
| 1/2″ | 20.96 | 18.63 |
| 5/8″ | 22.91 | 20.59 |
| 3/4″ | 26.44 | 24.12 |
| 7/8″ | 30.20 | 27.88 |
| 1″ | 33.25 | 30.29 |
| 1 + 1/4″ | 41.91 | 38.95 |
| 1 + 1/2″ | 47.80 | 44.85 |
| 1 + 3/4″ | 53.75 | 50.70 |
| 2″ | 59.61 | 56.66 |
| 2 + 1/4″ | 65.71 | 62.75 |
| 2 + 1/2″ | 75.18 | 72.23 |
| 2 + 3/4″ | 81.53 | 78.58 |
| 3″ | 87.88 | 84.93 |