DIY Network

Replacing Ductwork and Installing a Return Vent A bathroom pipe is leaking into the air conditioning. From "Finders Fixers" episode DFFX-102

After a thorough inspection, home inspector Wally Conway finds that the cause of the mysterious smell in Kate Woods and James Donaldson’s home is a leaky sewage pipe in the crawlspace.

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The pipe connection where Kate and her dad tied in during the bathroom remodel has failed and is dripping gray water from the kitchen sink onto the return air ducts. The ductwork has sagged to the ground. Now, whenever the AC system is turned on, return air is sucked across the standing sewage water in the sagging, rotting duct. The end result: the nasty, yucky smell is filtered throughout the house.

Note: Before replacing the pipe connection, shut off the plumbing.

Materials:

flexible air duct
saw
metal vent box
2x4 wooden boards
duct tape
nails
plastic ties
hammer
scissors
cordless drill
aluminum tape
screws
plastic rib
insulated duct board
measuring tape
mastic adhesive cement
paintbrush

1. Remove existing ductwork where needed. Run the new flexible air duct under the house from the floor return to the underside of the air handler and attach to the metal vent box, or plenum (figure A).

Note: If the air duct isn't long enough, you can add extra length. Attach a second air duct to the first by peeling back the insulation and tucking it into the first section approximately 6"-10" and seal with duct tape. Fold the insulation back in place and roll on the outer layer (figure B).

Figure A

Figure B

Figure C

2. Use plastic ties, placed every few feet, to attach the entire length of the duct to the bottom of the floor joists; this keeps the duct up and away from the ground.

3. Seal the new flex duct to the new box with plastic ties, keeping the connection between the duct and the box as tight as possible. Once everything is in place, clip the end of the ties, seal everything tight with aluminum tape and burnish with a plastic rib (figure C).

4. To hold the new vent in place, you may need to create a wooden frame or housing. Measure the opening and cut the 2x4s to size. Nail the frame into the opening and put the new vent in place (figure D). Center, using 2x4 braces, and screw in place (figure E).

Figure D

Figure E

5. Fill in the gaps between the floor and the new frame with insulated duct board. Cut the board to size, making sure it slides in and fits snugly on both sides of the frame (figure F).

6. If needed, further seal the vent with mastic adhesive cement, which is painted on, ensuring no air escapes around the vent (figure G.

7. Once the adhesive is dry, replace the grate (figure H).

Figure F

Figure G

Figure H

RESOURCES :

Insulated flexible duct
Master Flow 8" black jacket R8 (8IFD Series), model #8IFD8X300
Website: www.gaf.com