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IPC 905-906
Validated against the standard.
PDF export
Pro-only. Generate professional reports.
$2.99 Pro
Lifetime unlock. No subscriptions.
How it works
Enter your values
Type in your inputs — the app fills code tables and constants for you, so there's nothing to look up.
Get a code-checked result
Instant answer with a clear PASS / FAIL and the exact IPC 905-906 reference behind every number.
Save & export
Keep a history of calculations and export a clean PDF report to share or attach to a permit (Pro).
What this calculator does
Every trap needs a vent to protect its water seal from siphoning and back-pressure. This app sizes vents and checks trap-arm lengths per the IPC, so fixtures drain freely and sewer gas stays out of the building.
What it checks
- Trap size matched to the fixture and its drain.
- Trap-arm length — the distance from the trap weir to the vent, limited by pipe size so the trap cannot self-siphon.
- Vent size based on the DFU served and the developed length of the vent.
Worked example
A lavatory on a 1-1/2 inch trap arm has a maximum developed length to its vent (on the order of several feet) set by the IPC. Exceed it and you must increase the pipe size or relocate the vent — exactly what the app flags.
Related calculators
Size the drain with the drainage pipe sizing calculator and set fall with the drainage slope calculator.
Trap and vent FAQ
Why does the trap arm length matter?
If the vent is too far from the trap, draining flow can siphon the trap seal. The IPC limits trap-arm length by pipe size to prevent this.
How is the vent size determined?
Vent size depends on the drainage fixture units served and the developed length of the vent. The app reads the minimum size from the IPC vent tables.
Does it cover common vent types?
It addresses individual, common, and wet-venting arrangements at the sizing level so you can confirm the configuration is within code limits.
Does it work offline?
Yes, it runs 100% offline with no account. Free with rewarded ads; a one-time $2.99 Pro unlock adds PDF export and saved history.
Get Trap Vent Sizing on your phone
Free with rewarded ads · $2.99 lifetime Pro · iOS & Android. Works 100% offline on the job site.