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Doing a dryer duct, the right way...

3218 Views 7 Replies 3 Participants Last post by  Gary in WA
I am upgrading the duct on my dryer from a 3" diameter plastic duct to a 4" rigid galvanized steel duct.

Current configuration:
Dryer is located in an unheated basement on an exterior wall.
The plastic 3" duct makes a 90 degree turn "vertical" at the dryer. Runs about 8 ft then another 90 degree turn "horizontal" and attaches to a metal duct/hood with flapper. The duct/hood assembly runs through the rim joist and brick fascia.

Steps I have taken:
I enlarged the hole in the brick fascia and rim joist to 4-1/4". I used a carbide hole saw so it is a very smooth cut.
I bought Heartland 21000 dryer vent closure and painted it to match the exterior brick color.
I bought a few sections of 4" rigid galvanized steel duct, the kind that comes in un-rolled 4ft sections. Also bought two non-adjustable 90 degree galvanized duct pieces. There is not a lot of horizontal duct work, but I will keep the seams facing upward.

Where I need some guidance:

Assembling the duct sections..... Is UL approved metal tape the best product I can use? What about mastic reinforced with fiberglass mesh? I hear clamps can pinch things and screws collect lint. Any product links would be quite helpful.

Attaching the duct sections to cinder block wall.... I guess some type of pipe strap, again a link would be helpful.

The gap between the duct work and the brick fascia + rim joist..... Do I cement the duct into the brick fascia and fill the void in the rim joist with some sort of heat safe insulation?

Designing the duct in a way that it is easily cleanable.... Got nothing on this one.

Designing the duct it so it can be attached and removed from dryer easily.... Should I put a small piece of aluminum flex duct between the dryer and the rigid duct?
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If you used this style hose you would not need the soild pipe and all those elbows and conections.
You can get them up to 10 ft. long.
Home Depot sells nice 4" hose clamp just for this with thumb screws to tighten them up.
Just use spray foam where it goes though the wall.
Your way over thinking this one simple problum.
You need to do more research on how much adding two elbows will reduce the CFM.
It would be like adding 10 extra feet to the lines and increace the drying time far more then using a flex line.
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