/ Field knowledge · IMC 307
If the primary drain stops, where does the water go?
IMC 307 is water-damage prevention, not a pipe-size note. If the primary drain stops, the drawings have to say where the water goes and what shuts the unit down.
Educational 2024 IMC 307. Confirm the adopted FBC Mechanical edition. This is not a condensate design for your coil.
The proof chain on the M-sheets
- Primary drain route, slope (not less than 1 percent), material, and size not smaller than the appliance/pan connection.
- Approved place of disposal — not a street, alley, or a direct tie to a DWV pipe.
- Indoor discharge generally stays in the same occupancy / tenant / dwelling as the source.
- Overflow: auxiliary pan, separate overflow line, water-level detection, or equivalent where overflow can damage the building. Downflow / no secondary drain: monitor in the primary pan.
- Pump: failure shutdown interlock where a pump is the only path.
The common redline
“Drain to nearest approved receptor” with no receptor, no slope, no overflow, and no tenant boundary. Equipment above a finished ceiling, tenant space, or electrical room is the highest-risk version of that note.
Source: Daily Code Talk — IMC 307 · tool: overflow-path check · access: IMC 306.
What to send
Unit location (above ceiling / closet / roof), architectural RCP if any, photos of the space below, and whether this is new or a replacement. A share link is enough.
If the drain note is the comment
Send the unit location and the ceiling below it. Masterbuild will say whether 307 is a drawing problem or a field problem.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
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