Wrong Metal For Furance Exhaust ? - HVAC - DIY Chatroom Home Improvement Forum

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Old 07-29-2013, 05:33 PM   #1
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Wrong metal for furance exhaust ?

So Im up on the roof and i notice the out side of the Exhaust pipe Is rusted away and the cap is missing off the exhaust pipe. from the attic there is blown in insulted and its all dis colored from the metal rotten away, it left the white blown in insulted yellow like the pipe on the roof
What should be done to fix this issue?

is everything all good except the cap missing?

it seems to be a low gauge steel for the flashing kit/ pipe slide over the inner pipe which seems to have no damage.
or did it rot out so bad because there was 2 different types of metals used?

Next doors


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Old 07-29-2013, 06:21 PM   #2
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they use galvanized metal for those and it gets corroded and eaten away by moisture and acid rain does not help either. needs to be replaced with a new one, unfortunately none of them are made of stainless steel as the cost would be prohibitive.


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Old 07-29-2013, 06:26 PM   #3
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wow that has to be really leaking on a rain????ben sr replace is an understatment...
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Old 07-29-2013, 06:41 PM   #4
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So it needs a flashing kit and a sock type pipe to going iver the original one? I seen several of these very very old and not even phased by weather? Do you think it was the product they used as on the same street there is several rotted out so the builder probably used the same one threw out the street, the hvac guys I mean?

Its a very very thin gauge

What would the cost be of these parts and which would I need to buy?
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Old 07-29-2013, 09:15 PM   #5
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It's call double wall or type B vent. You should replace whatever is rusted through. What's your location, and what is common weathers there?
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Old 07-29-2013, 10:58 PM   #6
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The damage looks to be from the flue gases condensing at the cap and dripping down onto the outer galvanized pipe and destroying it. Either that or you live real close to the ocean.

No matter the reason they need to be replaced back to where the pipe is not damaged.
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Old 07-30-2013, 05:19 AM   #7
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You'll need to look at what brand it is. And then you have to use that brand. Unless you run all new from the furnace up.

The attic height may be such, that the B vent is cooling too much in the attic. May need to wrap it with a non combustible insulation in the attic.
When posting in certain forums, knowing your location will help others give better feedback/advice/solutions to your questions.
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Old 07-30-2013, 06:18 AM   #8
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There are stainless steel pipes available but as mentioned they are not an easy buy. I just passed on them myself in favor of the galvanized.


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