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I am planning to relocate my gas dryer to the center of my basement. The closest vent is in one of the walls 16ft/5m away. To reach it I would need to run an exhaust pipe horizontally, enclosed in the ceiling by drywall (so preferably no leaks).

What is the best material in this case? Any tips? Is moisture pooling in the pipe a concern?

Here is what I currently know:

PVC pipes +Can handle moisture -Combustible

Flexible metal foil +Not combustible -Might increase moisture pooling due to texture -Rust?

Sheet metal ducts +Not combustible +No moisture pooling -Leaks out of horizontal and lengthwise joints? -Rust?

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    What size joists and what width spacing in the ceiling? Feb 13 at 21:19
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    Check the manufacturers install guide to see the maximum vent distance including elbows.
    – mikes
    Feb 13 at 22:56
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Assuming the 16' distance, plus any other lengths and elbows falls within the manufacturer's guidelines, I would use sheet metal round ducts, usually 4" diameter. If you mount them so the lengthwise seam is at the top (or close to it), then you don't have an issue with any moisture that might collect on the bottom leaking out.

Join the duct sections with metal duct tape (no screws that could collect lint) and, if you want, run a length of metal duct tape along the seam.

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    I agree with metal and the seam at the top. I haven’t seen an issue with water pooling in metal ducts run inside enclosed air spaces even next to Air-conditioning ducts. I think the air flow although very humid at the start drys the pipe out at the end of anything we’re to condense in it. I would go with metal , I am not a fan of flex duct for dryers as it is impossible to clean where even in a wall metal pipe can using a string blown through the pipe pulling a hand towel through really picks up the lint that gets by the lint trap.
    – Ed Beal
    Feb 14 at 2:31
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I'd run it with sheet metal ducts for best airflow. Aluminum is available, which would eliminate any rust potential. If you have room in the ceiling area, you could angle the horizontal pipe, sloping downwards towards the exit to help with moisture/wetness. Use foil tape, which is quite sticky and should be good enough to prevent leaking.

If it's running from the basement floor into the ceiling above, and then another 16 feet horizontal, you're going to hit some lengthy distances just on the straights alone, not including probably minimum 2 elbows (one at dryer, one at wall/ceiling junction), which have additional length penalties.

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I don't believe PVC is allowed as it does not have a high enough fire rating. Additionally it is microscopically less smooth than metal and will build up lint faster.

Aluminum is usually very thin and I would not want something so flimsy inside my walls.

I would highly suggest 26 or 24 gauge galvanized steel ducts because at some point you will need to clean out the ducts so you want something that can withstand the abuse. Make sure to tape up all of the joints with UL approved tape. DO NOT use sheet metal screws.


As for pitch:

All horizontal runs should pitch 1/4-inch per foot to the outside. This will help to avoid moisture from sitting in the pipe or draining back to the dryer.

https://www.homedepot.com/c/ah/how-to-install-a-dryer-vent/9ba683603be9fa5395fab907b927963

Not sure if this is code or just good practice. The logic makes sense but might not be feasible for you.

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