How do I fix flex duct that kinks right off the plenum box

Plain-English answer

A tight 90 right off a plenum box can crush the flex core even if the outside jacket looks connected. The room may be starved because the bend is acting like a closed damper.

The usual recovery is to give the turn a rigid elbow/boot or a wider supported bend, then reconnect the flex straight and smooth. Check strap placement, light fixtures, ceiling grid, and whether the run can be shortened or routed cleaner.

Field checklist

• Look at the flex core shape, not just the outer jacket.
• Check if a light, grid, pipe, or wire is forcing the bend too tight.
• Verify the start collar is secure and not tearing the plenum.
• Use rigid elbow/boot or supported sweeping bend if approved.
• Recheck airflow/noise after the kink is removed.

Ask Foreman

Verify before acting

Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

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