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Trap arm length: trap to vent
IPC 2021 909.1 — check your local code
The longest a fixture's trap arm may run from the trap to the vent, by trap size, from IPC 2021 909.1. Measured along the arm.
Local codes differ — check your local code.
Verify with your local code and AHJ. Reference only, no warranty.
| Trap to vent, max | |
|---|---|
| 1 1/4″ | 5′ |
| 1 1/2″ | 6′ |
| 2″ | 8′ |
| 3″ | 12′ |
| 4″ | 16′ |
Left: trap size. Measured along the arm, from the trap to the vent.
Open this sheet in the toolkitQuestions
How far can a 1 1/2 inch trap be from the vent?
6′ under IPC 2021 909.1. Check your local code.
What is the trap arm length for a 2 inch trap?
8′ from the trap to the vent under IPC 2021 909.1.
How is a trap arm measured?
Along the arm, from the trap weir to the vent.