T Definitions

Definition Categories

Tail piece

A tail piece is a short piece of vertical pipe that runs from the plumbing fixture waste outlet (drain) to the inlet side of the fixture’s trap.


A tee is a fitting with 3 or more openings. Two openings are in a straight line and one opening is at an approximate 90° angle to the others. Double tees and tees with side inlets are also available. Use vent tees only in the dry vent sections of vent pipes.


The throat is the opening above the firebox through which combustion products leave the firebox.


A townhouse building contains three or more attached single family dwelling units in one building. A townhouse must: (a) be continuous from the foundation to the roof (not one dwelling unit on top of another), (b) have at least (≥) two sides exposed to a yard or public way, and (c) have a separate means of egress for each dwelling unit. Read the full Definition

Trap (P trap)

A trap is a fitting, usually located either inside or under fixtures, that prevents sewer gasses from escaping from the plumbing waste pipes. Traps maintain a water seal (trap seal) extending from the trap’s crown weir to its dip. Vents help protect the water seal from siphoning.

Trap arm

The trap arm is the part of the fixture drain pipe between the trap outlet and the fitting connecting the trap arm to the vent. If the vent fitting is also the drain fitting, then the entire trap arm is also the fixture drain. If the vent fitting is before the drain fitting, then only the pipe before the vent fitting is the trap arm.