Cant find rigid 4" aluminum duct for dryer

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Old 01-10-15, 07:12 AM
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Cant find rigid 4" aluminum duct for dryer

Ok, I am going crazy.

I am moving my dryer and want to duct it in rigid aluminum.

I have a piece of 4" that is 2 feet long. But I want longer lengths, like 5 feet.

I see galvanized that is longer but I cannot find rigid aluminum that is more than 2 feet.

Why cant I find 4" round rigid aluminum more than 2 feet anywhere"?
 
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Old 01-10-15, 07:56 AM
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Why do you need aluminum? Why won't galvanized longer pieces for the main run work?,
 
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Old 01-10-15, 08:25 AM
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If you're looking for aluminum at the big box stores you'll find it flat on the shelf.
It gets cut to length and then the seam is snapped together.
 
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Old 01-10-15, 08:41 AM
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It just seems the aluminum is smoother--less lint buildup. Is that not correct?
 
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Old 01-10-15, 09:05 AM
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Either will work ok. The galvanized steel is more durable and will ultimately last longer.
The aluminum crushes easily.
 
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Old 01-10-15, 09:44 PM
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Use galvanized, not aluminum.
Not it's not going to cause a lint build up problem.
Use foil tape on the seams, not screws or duct tape.
One dryer fire and that aluminum will melt like hot butter.
 
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Old 01-11-15, 05:12 AM
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If you are putting the duct in the walls the piping must be steel to contain a lint fire. Aluminum can only be used for the short final connection to the dryer.
 
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Old 01-11-15, 06:02 AM
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It is all going to be open. But wouldnt aluminum contain a fire also as long as it isnt that really thin stretchable. I was able to find 30 gauge aluminum the length I need in my plumbing supply store.

Is galvanized better?
 
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Old 01-11-15, 06:10 AM
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You could burn a hole through aluminum tubing with a lighter.
Galvanized is the way to go.
Been to two dryer fires so far this winter, both had used aluminum, one flexible, one solid pipe.
That thin aluminum is also far harder to work with, it ends up collapsing just trying to assemble it.
 
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Old 01-12-15, 07:05 AM
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Is the ductwork the most common place for a dryer fire?

I currently have the flexible and since I am changing the location of my dryer I figured I would do it right. I am also making it a bit longer of a run. I am going to be using three 5 foot sections and three elbows--the bendable elbows that swivel in multiple angles/directions (do they make them in galvanized also?)

I dont think that is too long but I tend to be a worrier and have been thinking about this alot. Unfortunately, with my basement renovation plans, I kind of need to move the dryer to this new location with the longer duct.
 
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Old 01-12-15, 07:21 AM
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The vent pipe is almost always the source of the fire, at least that's what I've seen in all the dryer fires I've seen while being on a fire dept. off and on for the past 40 years.
And all of them have had flex lines that melted through and there was nothing left of them.
We have at least 3 dryer fires a year and not one had solid pipe.
A laundry room ideally should be located on an outside wall with the shortest run and with the least amount of elbows as possible.
 
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Old 01-12-15, 07:22 AM
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Any place lint will build up is a positional place for a lint fire. Use hard flex to connect to dryer and the hard the rest of way
 
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Old 01-12-15, 07:28 AM
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"...the most common place for a fire?" Who cares? It's a fire risk and it's easy to make safer by using steel duct.

Almost all rigid duct elbows are steel as is the duct tubing. Steel is the commonly available from most building suppliers and home centers while aluminum is not.

Since you're going to have at least 15 feet of duct and three elbows you should check the specs for your dryer. Some dryers have more powerful blowers specifically to accommodate longer vent runs.

Here is a recommendation for dryer duct length:
M1502.6 Duct length.
The maximum length of a clothes dryer exhaust duct shall not exceed 25 feet (7,620 mm) from the dryer location to the wall or roof termination. The maximum length of the duct shall be reduced 2.5 feet (762 mm) for each 45-degree (0.8 rad) bend, and 5 feet (1,524 mm) for each 90-degree (1.6 rad) bend. The maximum length of the exhaust duct does not include the transition duct.


The entire article may be found here and it also discuses the fire risk:
Dryer Vent Safety - Int'l Association of Certified Home Inspectors (InterNACHI)
 
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Old 01-13-15, 09:05 AM
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With solid duct/angled vent/3 elbows, the manual says 29 feet. I plan to run it only 15 feet. So I should be good. If I upgrade my vent to boxed or louvered I can run 35 feet.

I feel good about the length of the run since it isnt really even borderline.

I will go with galvanized.

But now a couple of questions on the solid venting...

The joints get taped with metal tape. But how do you clean/inspect the vents regulary (once a year?) Just remove the tape and re-tape it each time?

And as for connecting to the dryer:
Use hard flex to connect to dryer and the hard the rest of way
Is hard flex the one that stretches to about 8 feet? Also called semi-rigid? I wanted to avoid that because it squeezes and dents so easily.

But you need to be able to slide the dryer out a little from time to time so I guess it is needed. What do you use, like a 3 foot section out of the dryer and then solid the rest of the way?
 
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Old 01-13-15, 10:26 AM
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It comes in a 6 foot section compressed to 3 foot. Will expand easily and if you put a 4 or 5 inch 2x4 behind dryer it will not push back and crush. Use 2 90 dryer vent bends will not affect venting a lot. If a new install of venting do not put it center of dryer as than you have the 2 90"s connect and you can't push dryer back as far as you would like.
 
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Old 01-13-15, 10:43 AM
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I'm going to go out on a limb here. I have no data to back this up.

To avoid lint build up:

Clean screen after each load.

Clean the internal dryer duct (channel) regularly. Purchase and use brush similar to this:

Name:  ventbrush.jpg
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Of course it's good to clean the ductwork itself, that's harder.
I think if you keep your lint screen clean and clean the internal parts of dryer, you will go a long way to prevent a fire.
 
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Old 01-13-15, 11:14 AM
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The way that I have done my own and some others avoids flex altogether. The rigid duct slips rather easily over the connector on the dryer, as long as it's lined up right, so I have everything taped from the wall back, get the dryer close, use a mirror when needed to make sure it's where it needs to be, and slide the dryer straight back into the duct. So the duct is not taped to the machine, and I have used a yard stick to work the duct the last inch or so, or a piece of string to hold the duct from sagging a little, but, in my opinion, it beats flex.
 
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Old 01-13-15, 12:29 PM
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If a new install of venting do not put it center of dryer as than you have the 2 90"s connect and you can't push dryer back as far as you would like.
Sorry, but I dont understand this. It sounds like 2 90s connecting to the dryer, but there would be no need for two of them... I dont think.
 
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Old 01-13-15, 12:46 PM
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You're right, there is no need for two 90's.
Use galvanized duct, do as Pedro said and align duct, reduce elbows as much as you can.

At 15', you should be fine. The dryer will be pulled away from the wall rarely if ever.
 
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Old 01-13-15, 02:21 PM
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I suppose if willing to give up another couple of inches in the back (I think I might be due to my layout) I could put a short piece of pipe connected to the dryer (acting like short hub, maybe 3 inches or so). Tape that to the dryer. Then connect the 90 to the hub. Im guessing that might be a bit easier to align.
 
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Old 01-13-15, 03:31 PM
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If you are cramped for space directly behind the dryer, one of these Dundas Jafine Adjustable 28 in. to 45 in. Space Saver Aluminum Dryer Duct-UD48S - The Home Depot may help alleviate that and allow vertical ducting of the 4" pipe.
 
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Old 01-13-15, 04:13 PM
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Also, many dryers provide for either side or back discharge, and some anyway make it real easy. I have switched a couple on which all that was necessary was to remove a manufacturer provided knockout and either install or remove a standard $4 (or whatever) elbow. As far as the "slip joint" or whatever you want to call it, the one that slides together when you push the dryer back, I suggest that you try to do it at the dryer, not at one of the elbows, because the dryer connection is smooth to smooth if you will, whereas an elbow involves a crimped component, not as tight a seal.
 
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