Cross-Connection Air Gap (IPC 608.15.1)
The minimum air gap for the most positive backflow protection there is.
Example
You enter
- Effective opening diameter (in) 1
- Near wall false
- Measured installed air gap to check (in, optional) 2
You get
- Air gap (in) 2
- Air gap wall (in) 3
- Required air gap 2
Details, formula, and sources
The physical gap between a supply outlet and the flood-level rim, which nothing mechanical can defeat. IPC 608.15.1: the gap is twice the effective opening diameter but never less than 1 in, and three times the opening within three diameters of a wall. A 1 in opening needs a 2 in gap (3 in near a wall); a 1/2 in opening computes 1 in where the absolute minimum governs. Checks a measured installed gap against the requirement. For indirect-waste and tank-fill protection. A design aid, not a substitute for the plumbing code adopted by your AHJ.
air_gap = max(2 x opening, 1); air_gap_wall = max(3 x opening, 1); required = near_wall ? air_gap_wall : air_gap; passes = measured >= required.
IPC 2021 §608.15.1 (air gaps) and ASME A112.1.2 (Air Gaps in Plumbing Systems) by name.
Free read-only access at codes.iccsafe.org.
Estimate. AHJ and licensed plumber / gas fitter govern. Verify against the IPC / IFGC edition adopted in your jurisdiction.
Field names used by the API: opening_in, near_wall, measured_in, air_gap_in, air_gap_wall_in, required_in
- 2x / 3x rule minimum = 2x the effective opening (1 in floor), or 3x within three diameters of a wallIPC 608.15.1 / ASME A112.1.2
- Effective opening the diameter of the least cross-sectional area of the supply outletASME A112.1.2
- AHJ governs the adopted plumbing code and the AHJ govern the required gapscope of this tile