S-and-Drive Square Duct · Leak-test repair
Repair leakage
Failed S-and-drive joint
Task typeLeak-test repair
Tools / equipmentLeak detection, hand tools, sealant
Before you start
- Review the test report or locate the exact leakage point; do not assume every nearby stain is the source.
- Depressurize and isolate the test section.
- Expose enough of the joint to inspect hardware and metal condition.
Lay it out
- Trace leakage to the specific corner, side lock, S-cleat, seam, or nearby penetration.
- Check hanger alignment and joint stress that may have opened the leak.
Set and support it
- Support the duct before removing any drive or cleat.
- Relieve joint tension by correcting sagging or misaligned hangers.
Make the connection
- 1
Remove loose or failed sealant.
- 2
Inspect and correct the mechanical connection.
- 3
Replace damaged drive, S-cleat, fastener, or gasketed accessory as needed.
- 4
Clean and reseal the corrected location.
- 5
Allow cure as required.
- 6
Retest the section and document the result.
Check the install
- The actual mechanical cause was corrected.
- The repaired area passes retest.
- Adjacent joints and penetrations remain sound.
- Support alignment no longer pulls on the joint.
Common mistakes
- Smearing more sealant over a moving joint.
- Testing before repair material has cured.
- Ignoring leakage from a nearby tap, access door, or seam.
- Failing to correct the hanger that caused the joint to open.
Stop and ask
Stop if leakage is caused by incorrect duct construction, damaged panels, failed reinforcement, or a pressure class beyond the joint design.