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Apprentice Q&A · #351

Can duct be notched or squeezed around a storm drain pipe?

3rd YearRED · Stop and get directionStorm Drain Clash / 45 Offset

Short answer

Do not notch, flatten, or compress the duct around a plumbing line. Treat it as a coordination clash and bring measured offset options for approval.

Field answer

A cast-iron storm drain or roof drain line is a hard obstruction. Duct should not be smashed around it, and another trade’s pipe should not end up touching the duct.

Measure the obstruction, clearance, and available space. The likely recovery is an approved 45° offset, revised route, split/transition detail, or coordination correction. Keep clearance for vibration, insulation, condensation, and service access.

What to check first

Do not do this

Do not notch or flatten the duct to sneak around a storm drain pipe.

Why it matters

Bad clash fixes can restrict airflow, create condensation contact, and cause rework between trades.

Ask foreman

The storm drain crosses our duct path at [location]. I measured the pipe, slope, and duct elevation. The clean options look like a 45 offset or revised route. Which direction do you want?

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Related Field Rescue route

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Final direction belongs to the foreman, approved drawings/specs, manufacturer instructions, pressure/material schedule, employer policy, and AHJ/code requirements.