What Are ASME B16.9 Tees?
ASME B16.9 buttwelding tees branch a piping run into a side outlet, from NPS 1/2 through NPS 48. Equal (straight) tees have all three ends the same size; reducing tees have a smaller branch outlet. Table 6.1-7 below lists equal tees and crosses; Table 6.1-8 covers reducing outlet tees and crosses.
Dimensions — Equal Tees (Table 6.1-7)
NPS 1/2 – 48. Values in mm (inch). C = center-to-end of run; M = center-to-end of outlet.
| NPS | Outside Diameter (mm / in) | C — Center-to-End Run (mm / in) | M — Center-to-End Outlet (mm / in) |
|---|---|---|---|
| 1/2 | 21.3 (0.84) | 25.0 (1.0) | 25.0 (1.0) |
| 3/4 | 26.7 (1.05) | 29.0 (1.12) | 29.0 (1.12) |
| 1 | 33.4 (1.32) | 38.0 (1.5) | 38.0 (1.5) |
| 1-1/4 | 42.2 (1.66) | 48.0 (1.88) | 48.0 (1.88) |
| 1-1/2 | 48.3 (1.9) | 57.0 (2.25) | 57.0 (2.25) |
| 2 | 60.3 (2.38) | 64.0 (2.5) | 64.0 (2.5) |
| 2-1/2 | 73.0 (2.88) | 76.0 (3.0) | 76.0 (3.0) |
| 3 | 88.9 (3.5) | 86.0 (3.38) | 86.0 (3.38) |
| 3-1/2 | 101.6 (4.0) | 95.0 (3.75) | 95.0 (3.75) |
| 4 | 114.3 (4.5) | 105.0 (4.12) | 105.0 (4.12) |
| 5 | 141.3 (5.56) | 124.0 (4.88) | 124.0 (4.88) |
| 6 | 168.3 (6.62) | 143.0 (5.62) | 143.0 (5.62) |
| 8 | 219.1 (8.62) | 178.0 (7.0) | 178.0 (7.0) |
| 10 | 273.0 (10.75) | 216.0 (8.5) | 216.0 (8.5) |
| 12 | 323.8 (12.75) | 254.0 (10.0) | 254.0 (10.0) |
| 14 | 355.6 (14.0) | 279.0 (11.0) | 279.0 (11.0) |
| 16 | 406.4 (16.0) | 305.0 (12.0) | 305.0 (12.0) |
| 18 | 457.0 (18.0) | 343.0 (13.5) | 343.0 (13.5) |
| 20 | 508.0 (20.0) | 381.0 (15.0) | 381.0 (15.0) |
| 22 | 559.0 (22.0) | 419.0 (16.5) | 419.0 (16.5) |
| 24 | 610.0 (24.0) | 432.0 (17.0) | 432.0 (17.0) |
| 26 | 660.0 (26.0) | 495.0 (19.5) | 495.0 (19.5) |
| 28 | 711.0 (28.0) | 521.0 (20.5) | 521.0 (20.5) |
| 30 | 762.0 (30.0) | 559.0 (22.0) | 559.0 (22.0) |
| 32 | 813.0 (32.0) | 597.0 (23.5) | 597.0 (23.5) |
| 34 | 864.0 (34.0) | 635.0 (25.0) | 635.0 (25.0) |
| 36 | 914.0 (36.0) | 673.0 (26.5) | 673.0 (26.5) |
| 38 | 965.0 (38.0) | 711.0 (28.0) | 711.0 (28.0) |
| 40 | 1016.0 (40.0) | 749.0 (29.5) | 749.0 (29.5) |
| 42 | 1067.0 (42.0) | 762.0 (30.0) | 711.0 (28.0) |
| 44 | 1118.0 (44.0) | 813.0 (32.0) | 762.0 (30.0) |
| 46 | 1168.0 (46.0) | 851.0 (33.5) | 800.0 (31.5) |
| 48 | 1219.0 (48.0) | 889.0 (35.0) | 838.0 (33.0) |
Reducing Tees (Table 6.1-8)
Reducing outlet tees cover the full range NPS 1/2×1/2×3/8 through NPS 48×48×22 (213 size combinations per Table 6.1-8). The table below shows commonly requested sizes (NPS 1/2 through 12 run); the complete table is per ASME B16.9 Table 6.1-8.
| NPS (Run × Run × Branch) | Run OD (mm / in) | Branch OD (mm / in) | C — Run (mm / in) | M — Branch (mm / in) |
|---|---|---|---|---|
| 1/2 × 1/2 × 3/8 | 21.3 (0.84) | 17.3 (0.68) | 25.0 (1.0) | 25.0 (1.0) |
| 1/2 × 1/2 × 1/4 | 21.3 (0.84) | 13.7 (0.54) | 25.0 (1.0) | 25.0 (1.0) |
| 3/4 × 3/4 × 1/2 | 26.7 (1.05) | 21.3 (0.84) | 29.0 (1.12) | 29.0 (1.12) |
| 3/4 × 3/4 × 3/8 | 26.7 (1.05) | 17.3 (0.68) | 29.0 (1.12) | 29.0 (1.12) |
| 1 × 1 × 3/4 | 33.4 (1.32) | 26.7 (1.05) | 38.0 (1.5) | 38.0 (1.5) |
| 1 × 1 × 1/2 | 33.4 (1.32) | 21.3 (0.84) | 38.0 (1.5) | 38.0 (1.5) |
| 2 × 2 × 1-1/2 | 60.3 (2.38) | 48.3 (1.9) | 64.0 (2.5) | 60.0 (2.38) |
| 2 × 2 × 1-1/4 | 60.3 (2.38) | 42.2 (1.66) | 64.0 (2.5) | 57.0 (2.25) |
| 2 × 2 × 1 | 60.3 (2.38) | 33.4 (1.32) | 64.0 (2.5) | 51.0 (2.0) |
| 2 × 2 × 3/4 | 60.3 (2.38) | 26.7 (1.05) | 64.0 (2.5) | 44.0 (1.75) |
| 3 × 3 × 2-1/2 | 88.9 (3.5) | 73.0 (2.88) | 86.0 (3.38) | 83.0 (3.25) |
| 3 × 3 × 2 | 88.9 (3.5) | 60.3 (2.38) | 86.0 (3.38) | 76.0 (3.0) |
| 3 × 3 × 1-1/2 | 88.9 (3.5) | 48.3 (1.9) | 86.0 (3.38) | 73.0 (2.88) |
| 3 × 3 × 1-1/4 | 88.9 (3.5) | 42.2 (1.66) | 86.0 (3.38) | 70.0 (2.75) |
| 4 × 4 × 3-1/2 | 114.3 (4.5) | 101.6 (4.0) | 105.0 (4.12) | 102.0 (4.0) |
| 4 × 4 × 3 | 114.3 (4.5) | 88.9 (3.5) | 105.0 (4.12) | 98.0 (3.88) |
| 4 × 4 × 2-1/2 | 114.3 (4.5) | 73.0 (2.88) | 105.0 (4.12) | 95.0 (3.75) |
| 4 × 4 × 2 | 114.3 (4.5) | 60.3 (2.38) | 105.0 (4.12) | 89.0 (3.5) |
| 4 × 4 × 1-1/2 | 114.3 (4.5) | 48.3 (1.9) | 105.0 (4.12) | 86.0 (3.38) |
| 5 × 5 × 4 | 141.3 (5.56) | 114.3 (4.5) | 124.0 (4.88) | 117.0 (4.62) |
| 5 × 5 × 3-1/2 | 141.3 (5.56) | 101.6 (4.0) | 124.0 (4.88) | 114.0 (4.5) |
| 5 × 5 × 3 | 141.3 (5.56) | 88.9 (3.5) | 124.0 (4.88) | 111.0 (4.38) |
| 5 × 5 × 2-1/2 | 141.3 (5.56) | 73.0 (2.88) | 124.0 (4.88) | 108.0 (4.25) |
| 5 × 5 × 2 | 141.3 (5.56) | 60.3 (2.38) | 124.0 (4.88) | 105.0 (4.12) |
Materials & Temperature Range
Tees are manufactured in A234 WPB carbon steel (-29°C to 425°C), A403 WP304 / WP316 stainless (up to 538°C), and A420 WPL6 low-temperature carbon steel, matching the schedule of the pipe they are welded to.
Related Standards
- ASME B16.9 — Buttwelding Fittings (parent standard)
- ASME B16.9 Elbows — 90° & 45°
- ASME B16.9 Reducers — Concentric & Eccentric
- ASME B16.9 Pipe Caps
- ASME B16.9 180° Returns
- ASME B16.11 — Forged Socket-Weld & Threaded Fittings
- ASTM A403 WP304 Stainless
- Our Fittings Range
FAQ
What is the difference between an equal tee and a reducing tee?
An equal tee has three ends of the same NPS size. A reducing tee has a branch outlet smaller than the run — e.g. 4×4×3.
What sizes do B16.9 tees cover?
Equal tees NPS 1/2–48 (Table 6.1-7). Reducing tees range from NPS 1/2×1/2×3/8 up to 48×48×22 (Table 6.1-8, 213 combinations).
What do dimensions C and M mean?
C is the center-to-end length of the run; M is the center-to-end height of the branch outlet.
Can B16.9 tees be used with B16.5 flanges?
Yes — the welding-end dimensions match ASME B36.10/B36.19 pipe and B16.5 flange bores for a complete butt-welded system.
Which materials are standard?
A234 WPB carbon steel, A403 WP304/WP316 stainless, and A420 WPL6 low-temperature service — chemistry per the applicable ASTM standard.
Do you supply reducing tees in sizes not listed above?
Yes — the full 213-size range of Table 6.1-8 is available. Send your exact NPS combination for a quote.
Need This Standard for Your Project?
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