DIY Network

Flue Symptoms Rick Yeager searches a home to find the source of a mysterious scratching behind the walls. From "Finders Fixers" episode DFFX-106

Home inspector Rick Yerger traces the noises in the wall of Steve and Christy Karsten's home to a gas combustion furnace and the water heater. Something in the flue system is causing a backdraft and allowing deadly carbon monoxide to flow into the Karstens' home. Combustion gas is remaining in the flue in the wall; the backup is causing condensation and rain inside the space. Repairs, made from the garage through the upstairs to the roof, include removing drywall and flue ducts.

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Steve and Christy also learn how to install vent duct from the gas furnace and water heater to ensure proper drafting and prevent carbon monoxide poisoning and the possibility of fire. Proper strapping, hanging flue duct and drywall repairs are also demonstrated.

Remove and Replace Flue

Materials:

drywall or electric saw
safety glasses
gloves
face mask
flat bar
screwdriver and/or cordless drill
screws
metal strap

1. Unplug the furnace and turn the water heater down to the "vacation" setting to contain the CO gas (figure A).

2. To remove the flues, unscrew every connection at each of the joints and dismantle (figure B).

3. Cut through the drywall with a drywall or electric saw, adjusting the blade to ensure it cuts only through the depth of the drywall; this will avoid the risk of cutting through any electrical wiring or the flue itself. Be sure to wear protective gear such as safety glasses, gloves and a mask (figure C).

Figure A

Figure B

Figure C

4. As soon as the dysfunctional pipes are exposed, they can be removed. A flat bar is used to help dismantle the connected pieces (figure D).

5. Remove the flue and any additional frame boards that will obstruct the necessary clearance needed to avoid a fire hazard. A minimum clearance of 1" is required around the flue (figure E).

Figure D

Figure E

6. With the old flue out of the way, the new flue, which has been cut to size, is put in place. The first piece slides in place, going up through the roof (figure F).

Note: Make sure the directional arrow is pointing up.

7. As one person holds the first section up, slide the second section of the flue down into the floor and connect the two pieces together, again making sure the directional arrows are pointing up.

8. To keep the flue securely in place and ensure clearance from the wall, install tightened metal straps. Cinch the screws in at an angle to pull the strap taut and remove any slack (figure G).

Figure F

Figure G

Figure H

Up on the Roof

Materials:

roofing mastic
storm collar
rain cap

1. Once the flue is in place, head up to the roof. Apply a layer of roofing mastic around the flue piece to seal the joint between the new flue and the shingles (figure H).

2. Add a storm collar, again sealing with roofing mastic. Also, to keep moisture out, a rain cap is added, completing the exterior part of the fix (figure I) (figure J) (figure K).

Figure I

Figure J

Figure K

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