| Mains | Branch | Main vertical
-----------------+----------------+------------+----------------
1-1/4-inch vent | 20 feet | 1 |
1-1/2-inch vent | 40 feet | 2 or less |
2-inch vent | 65 feet | 10 or less | 20 or less
2-1/2-inch vent | 100 feet | 20 or less | 40 or less
3-inch vent | 10 or more | 60 or less | 100 or less
| stories | |
-----------------+----------------+------------+----------------

The branch vent shall not be less than the following sizes:

1-1/4 inches in diameter for 1-1/4 inch trap.
1-1/2 inches in diameter for 1-1/2 inch to 2-1/2 inch trap.
2 inches in diameter for 3 inch to 4 inch trap.
One-half their diameter, for traps 3 inches and over.

Where two or more closets are placed side by side, on a
horizontal branch, the branch line shall have a relief
extended as a loop. A pipe 2 inches in diameter shall be
sufficient as a loop vent for two closets. A pipe 3 inches in
diameter shall be sufficient as a relief for three or four
closets; and where more than four closets are located on the
same branch the relief shall not be less than 4 inches in
diameter. All house drains and soil lines on which a water
closet is located must have a 4-inch main vent line. Where an
additional closet is located in the cellar or basement, and
within 10 feet of main soil or vent line, no relief vent will
be required for said closet; but where it is more than 10
feet, a 2-inch vent line will be required. Relief vent pipes
for water closets must not be less than 2 inches in diameter,
for a length of 40 feet, and not less than 3 inches in
diameter, for more than 40 feet.

No re-vent from traps under bell traps will be required.

In any building having a sewer connection with a private or
public sewer used for bell-trap connections or floor drainage
only, a 2-inch relief line must be extended to the roof of the
building from rear end of main. House drains, constructed for
roof drainage only, will not require a relief vent.

A floor trap for a shower shall be vented, unless located in
the cellar or ground floor the paving of which renders the
trap inaccessible.

SEC. 30. HORIZONTAL VENT PIPES.--Where rows of fixt