Using tables from the National Fuel Gas Code or our Sizing & Application Guide, determine the diameter of venting required. The Sizing & Application Guide also offers tips on good design including multi-appliance system sizing and design. The System Design and Installation Guide is an additional resource.
Branch and trunk diameters of the standard tee are the same size. For small branch sizes, use a reducing tee up to 6" size. For larger sizes, use an increaser with a standard tee.
Model | Size | A | B |
---|---|---|---|
3ET | 3" | 7 1/8" | 4 1/8" |
4ET | 4" | 8 7/8" | 4 5/8" |
5ET | 5" | 10" | 5 1/4" |
6ET | 6" | 11 1/2" | 5 3/4" |
7RT | 7" | 13" | 6 1/2" |
8RT | 8" | 14" | 6 7/8" |
9RT | 9" | 15" | 7 3/4" |
10RT | 10" | 16" | 8 1/16" |
12RT | 12" | 17 9/16" | 9 3/4" |
14RT | 14" | 24" | 11 3/4" |
16RT | 16" | 26" | 13" |
18RT | 18" | 28 1/2" | 14 1/4" |
20RT | 20" | 30" | 15 1/2" |
22RT | 22" | 33" | 16 3/4" |
24RT | 24" | 36" | 18" |
26RT | 26" | 38" | 19" |
28RT | 28" | 40" | 20" |
30RT | 30" | 42" | 21" |