Trap & Vent Calc Plumb

Trap & Vent Sizing Calculator helps you size trap arm distances and vent pipe diameters per the printed IPC: Table 909.1 (trap-to-vent distance), Section 906.2 (vent sizing rule) and Table 906.1 (stack vents). Instantly determine maximum allowable trap arm length and minimum vent pipe size for any DFU load and vent length. Useful for DWV system design, especially for island sinks and fixture groups requiring separate vent stacks. Works 100% offline on the job site. Eliminate trap and vent sizing errors, ensure full code compliance.

FEATURES
- Trap Arm Mode: Maximum trap-to-vent developed length per printed Table 909.1 (1-1/4" 5 ft through 4" 16 ft, with the required drain slope; water closets exempt per the 909.1 exception)
- Vent Sizing Mode: Minimum vent diameter per the printed 906.2 rule — at least half the drain served, never below 1-1/4", one nominal size larger when the developed length exceeds 40 ft
- Stack Vent Length Mode: Maximum developed length for stack vents and vent stacks per printed Table 906.1 (stack size + DFU; conservative next-higher DFU row)
- Printed Table 906.1 data for stacks 1-1/4" through 8" stored exactly as published (app input covers 1-1/4"-4" stacks)
- Printed Table 909.1 trap-arm distances with slopes (1/4" per ft through 2"; 1/8" per ft for 3" and 4")
- 5 Trap/Drain Sizes: 1-1/4", 1-1/2", 2", 3", 4"
- Code Notes: Every result cites the exact IPC table or section used

HOW IT WORKS
1. Select calculation mode (trap arm length, vent size, or vent length)
2. Enter total DFU load on the vent
3. Enter trap size and vent pipe length
4. See IPC 2024 maximum distances and minimum vent sizes
5. Export chart to PDF for code inspection and permitting

PERFECT FOR
- Plumbers sizing trap arms for island sinks and fixture groups
- Journeyman plumbers and apprentices learning vent sizing
- Plumbing contractors designing complex vent systems
- Mechanical estimators calculating material requirements
- Plumbing inspectors verifying code compliance
- Building code officials conducting plan reviews

OPTIONAL PRO UPGRADE — $2.99 ONE-TIME IN-APP PURCHASE
The following features require a separate one-time in-app purchase. They are not required to use the calculator:
• Unlimited saved calculation history
• PDF export of results
• Dark theme
• Ad-free experience

STANDARDS & COMPLIANCE
IPC 2024 Table 906.1 - Vent Sizing for Continuous Ve