Reducing Tee Dimensions
A tee whose branch is smaller than the run. ASME B16.9 sets the run dimension C from the RUN size alone, so it is identical to the straight tee of that size — an 8 x 6 and an 8 x 4 tee are both 7.00 in centre-to-end on the run.
- Standard
- ASME B16.9
- Dimension
- Run centre-to-end C
- Size range
- NPS 3/4 – NPS 24
- Sizes published
- 20
Dimensions are given in inches, with the millimetre equivalent beneath in grey.
| Size | Matching pipe OD | Run centre-to-end C |
|---|---|---|
| NPS 3/4 | 1.050 in | 1.1228.45 mm |
| NPS 1 | 1.315 in | 1.5038.10 mm |
| NPS 1 1/4 | 1.660 in | 1.8847.75 mm |
| NPS 1 1/2 | 1.900 in | 2.2557.15 mm |
| NPS 2 | 2.375 in | 2.5063.50 mm |
| NPS 2 1/2 | 2.875 in | 3.0076.20 mm |
| NPS 3 | 3.500 in | 3.3885.85 mm |
| NPS 3 1/2 | 4.000 in | 3.7595.25 mm |
| NPS 4 | 4.500 in | 4.12104.65 mm |
| NPS 5 | 5.563 in | 4.88123.95 mm |
| NPS 6 | 6.625 in | 5.62142.75 mm |
| NPS 8 | 8.625 in | 7.00177.80 mm |
| NPS 10 | 10.750 in | 8.50215.90 mm |
| NPS 12 | 12.750 in | 10.00254.00 mm |
| NPS 14 | 14.000 in | 11.00279.40 mm |
| NPS 16 | 16.000 in | 12.00304.80 mm |
| NPS 18 | 18.000 in | 13.50342.90 mm |
| NPS 20 | 20.000 in | 15.00381.00 mm |
| NPS 22 | 22.000 in | 16.50419.10 mm |
| NPS 24 | 24.000 in | 17.00431.80 mm |
B16.9 dimensions are a function of NPS only and do not change with schedule or wall thickness.
Same size, any schedule. Because these dimensions depend on NPS alone, a spool drawing can be dimensioned before the schedule is fixed. The wall thickness still has to be ordered to match the pipe, or the weld prep will not line up.
Not tabulated here. The branch dimension M is not reproduced here. Unlike C, it depends on the size PAIR, and B16.9 tabulates it combination by combination in Table 8 rather than deriving it from a rule. Read M for your exact run x branch from a current copy of the standard or the manufacturer's catalogue; do not assume it equals the straight tee value for either size.
Common questions
What is the run centre-to-end c of an NPS 8 reducing tee?
7.00 in (177.8 mm). ASME B16.9 dimensions depend on NPS only, so this figure is the same in every schedule.
Does the reducing tee dimension change with wall thickness?
No. ASME B16.9 sets fitting dimensions from NPS alone. A schedule 40 and a schedule 160 fitting of the same size have identical centre-to-end dimensions — only the wall thickness and the bore differ, so the fitting still matches its pipe at the weld.
What material are reducing tees made from?
Carbon steel fittings are normally ASTM A234 WPB, matched to A106 Gr B pipe. Low-temperature service uses A420 WPL6, stainless uses A403 WP304/WP316, and chrome-moly uses A234 WP11, WP22 or WP91. See the material grade reference.