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

Flex cannot make a sharp unsupported turn off a collar without choking. Use a smoother path, hard elbow/boot where needed, and support the flex so the core stays open.

['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.']

Stop if

• 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.

Check

• A kinked flex start can starve a diffuser, create noise, and waste time during TAB.

Steps

• 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.

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