Flex Duct Connection Repair Procedure

The inner wrap should be completely removed and any wet duct board or insulation should be replaced. Also, the mating surfaces must be thoroughly dry before the repair can be performed. The mixing box collars and boot throats on the connections should be sealed and completely coated with a 1/8th inch layer of UL 181 approved mastic. The inner wrap should then be slid over the mastic covered mating surface, mechanically fastened, and the outer surface of the inner wrap and the interface should be sealed and coated with another layer of UL 181 approved mastic. The outer wrap should then be pulled over the connection, snugged to the mating surface, mechanically fastened, taped to the mating surface, and sealed with another layer of UL 181 approved mastic to the interface. The boots must be completely covered with a blanket of insulation and the mastic must be allowed to dry thoroughly before the system is restarted.

Metal Duct Repair Procedure

The insulation should be completely removed from the metal joint. The mating surfaces must be thoroughly dry before the repair can be performed. The trunk or distribution box collars and boot throats on the connections should be sealed and completely coated with and 1/8th inch layer of UL 181 approved mastic. The metal duct should then be slid over the mastic covered mating surface, mechanically fastened with a rivet or screw, and the outer surface of the duct and the interface should then be sealed with another layer of UL 181 approved mastic. The mastic requires 24 hours to dry. Once it is dry the duct should be pressurized and checked for leaks using a smoke pencil. If no leaks exist then the joint can be insulated. The insulation should completely cover the connection and should be snugged to the mating surface, mechanically fastened, and sealed with another layer of mastic. The boots must be completely covered with a blanket of insulation and the mastic must be allowed to dry thoroughly before the system is restarted.