Before Sealing a Flange Leak

Use before mastic/tape/caulk gets thrown at a leaking TDC/Ductmate/flanged joint.

A rectangular flanged joint leaks, looks open, is misaligned, has gasket trouble, or fails prep for test.

Stop if

• Ask when the joint is physically wrong, damaged, missing parts, wrong system, or when sealing method/spec is unclear.

Watch out

• Do not bury missing gasket under mastic.
• Do not seal over dirty/oily metal.
• Do not overdrive screws and deform the joint.
• Do not cover labels/access/inspection points.

Check

• Flange corner
• Gasket line
• Hardware/cleat condition
• Leak point

Steps

• Check mechanical fit-up first. Sealant is not a substitute for a bad joint.
• Check whether duct ends are square and pulled together evenly.
• Check gasket continuity, corners, missing hardware, loose cleats/bolts, and damaged flange.
• Check if screws/cleats are installed correctly for the joint system.
• Clean surfaces before sealant/tape.
• Use only approved sealant/tape/mastic for the job.
• Ask if the flange is bent, missing gasket, wrong size, or cannot pull square.

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