duct taping exhaust pipes

[Uno]

I just was cleaning my water heater and see the exhaust pipe on it has come loose in the middle. Can I just duct tape it for now and not expect it to melt?

[Ed Pawlowski]

Not a good idea. Put it back together and then drill a small hole and put a sheet metal screw through it.

[aemeijers]

And then use foil tape to seal it. (yeah, I know, it leaks at the bottom anyway, but just on general principles...)

[DD_BobK]

I have used aluminum foil duct tape for YEARS to "fix" the adjustable elbows and secure joints on flue pipes with no ill effect. I don't know if it's "ok' but it has worked fine for me w/o problems.

Do not use the fabric or plastic duct tapes for this application.

cheers Bob

[mm]

I don't know what you can and can't expect, but I would expect it to melt.

Use foil tape meant for that purpose.

[don &/or Lucille]

[jw]

It's not as expensive as replacing his home after the duct tape ignites and burns his house down. Duct tape is made for ducts (warm forced air), not HOT exhaust pipes.

[hibb]

Sounds dangerous to me. Isn't exhaust pipe leaks where carbon monoxide gets into the house or do water heaters burn so little fuel that it doesn't give off much exhaust?

[N8N]

no, it's definitely a concern. Most residential water heaters are in the neighborhood of 30-40K BTU or higher IIRC. I would follow the advice already given and screw it together. If it was put together properly in the beginning, the smaller, crimped ends of all the connections should be pointing in the direction of the exhaust flow to minimize the possibility of backdraft, even without sealing the joints. I suppose if you are anal retentive using some muffler cement might work, covered with metal foil tape (as others have said, NOT any other kind of "duct" tape - that would be doomed to a presumably quick, smelly failure.)

nate

[Bob F]

In reality, most "duct tape" is not approved for ducts. It just doesn't last.

[Bob F]

My understanding is that the crimped ends should be pointed down to contain condensation within the pipe instead of letting it drip out at the joints. This is important for wood stoves.

[willshak]

For general use, I use the clear type (3M and others). I have used some of it outside and it has been there for years, Summer and Winter, without deterioration. Forget the silver grey type. It just delaminates over time and the remaining glue is almost impossible to remove cleanly.

[Tom Horne]

The proper name for Duct Tape is Duct Insulators Tape. It's original purpose was to hold the canvas in place over the insulation while the Duct Insulators sewed the canvas up thus making the installation more durable. That is why it is a cloth tape that is extremely sticky. It is meant to conform to the canvas used to cover the old style insulation used on ducts back in the day. It was never intended for use directly on ducts. It was certainly never meant for use on gas appliance vent tubing.

-- Tom Horne

[clare]

AKA "Duct tape" - not "duck tape" which is what the cloth stuff is ACTUALLY - originally made of "cotton duck" - a type of cloth

[mm]

I'm afraid if one went looking for duct tape, he would end up with tape for heating ducts, whichdon't get over 120F I would think.

Flues from furances and gas water heaters get a lot hotter than that, and the op is working on the flue, the exhaust pipe, from his water heater.

[mm]

Others said what I just did more strongly, so let me put it another way.

You're thinking of the difference between duct tape and duct tape, a worthwhile distinction, but neither of them is the tape for exhaust pipes. That is metal foil tape.

[AZ Nomad]

The foil made for exhaust pipes doesn't work worth a damn. The flexing caused by the pressure waves of the exhaust quickly cause the tape to fatigue and rip. I've never heard of such a patch lasting a whole month.

[mm]

Well now you have. ;) Mine was put on in November I think and lasted a whole winter. It weet on an oil furnace just two inches from the flue collector, the steel part screwed to the furnace immediately past the heat eachanger, so it gets hot.

Another piece was went about 8 inches up from there and 3 inches over, out of the hot air flow but I'm sure it got hot. It was wrapped around the damper (that's hinged and has an adjustable weight) by some furnace guy and was there for a few years when another furnace guy took it off.

[Nate Nagel]

I think he meant on the muffler of a car, which is a much harsher environment than the flue of a burner due to the cyclic stress imposed by the pulsing of the exhaust of a piston engine.

nate

[Uno]

Thanks all for replies. Once I read them all, I realized that screwing them together is what I wanted to do. If they are not together in a convincing way (screws are very convincing), there is definitely a CO exposure you don't want to have in the place where you hang out to prepare your meals. (Yes, here in New Mexico, many of us have water heaters in our kitchens.)

So here's how it went down:

1) Refrain from using hot water for a half hour so that ducts won't be hot. 2) Duct tape up the back of this joint so it stays together for the next 5 minutes. 3) Use an 1-1/4 screw to make a penetration right on the knuckle. When you get through the top, stop. 4) Use drill bit to prepare hole for screw. 5) Install screw. 6) Remove duct tape. 7) Thank the nice folks on usenet who helped me out here.

I think I'll foil tape it for good measure. Cheers,