Dryer vent piping

I have an electric dryer that vents through the crawl space to an outside o pening. The run is about 12-15 feet. It uses the flexable aluminum type pip e and I want to replace it with somethign stouter. One reason is I have ace ss to this space through my garage through a 3 ft x 3ft square opening and when I bring things in and out of this area it hits the pipe. I thought abo ut 4 inch pvc, but read you should not use it becasue of the temperature ra ting and the risk of static electricity casuing a fire. I really dont see i t getting hot enough to damage pvc.
I live in the country. There are not alot of codes. I am not so worried abo ut the codes as I want it to be right and mitigate and potential fire or ot her risks.
I went to Home Depot and looked around. They also sell round ac metal duct but it too seemed kind of flimsey.
Another thing I looked at was gas water heater vent pipe. It is solid, and comes in 4 inch. It would be expensive though. (I think a three foot sectio n was 16 bucks?) I am not sure how you would assemple this togther and atta ch it to the box above the the dryer.
Any suggestions are appreciated!
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On Tuesday, October 15, 2013 8:36:35 AM UTC-4, snipped-for-privacy@yahoo.com wrote:

opening. The run is about 12-15 feet. It uses the flexable aluminum type p ipe and I want to replace it with somethign stouter. One reason is I have a cess to this space through my garage through a 3 ft x 3ft square opening an d when I bring things in and out of this area it hits the pipe. I thought a bout 4 inch pvc, but read you should not use it becasue of the temperature rating and the risk of static electricity casuing a fire. I really dont see it getting hot enough to damage pvc.

bout the codes as I want it to be right and mitigate and potential fire or other risks.

t but it too seemed kind of flimsey.

d comes in 4 inch. It would be expensive though. (I think a three foot sect ion was 16 bucks?) I am not sure how you would assemple this togther and at tach it to the box above the the dryer.

Get a larger PVC/ABS etc pipe to protect the area you travel through and put the aluminum dryer pipe inside it. Or build a simple wood frame around it so you can't hit it. Any possibility of re-routing it somewhere else entirely?
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On Tue, 15 Oct 2013 05:36:35 -0700 (PDT), snipped-for-privacy@yahoo.com wrote:

They also make that pipe in galvanized and that is a lot stiffer
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On 10/15/2013 07:36 AM, snipped-for-privacy@yahoo.com wrote:

Home Depot sells semi-rigid dryer vent pipe for about $11 for 5'
I use it and it is "sturdy enough"
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On Tuesday, October 15, 2013 10:06:35 AM UTC-2:30, snipped-for-privacy@yahoo.com wrote:

opening. The run is about 12-15 feet. It uses the flexable aluminum type p ipe and I want to replace it with somethign stouter.
Good start...flexible aluminum pipe - even the semi-rigid stuff - isn't sui table (lint build-up + fire hazard). You need rigid duct with smooth inter ior surface. Avoid using screws, they act as lint catchers. Don't use duct -tape, it can't handle the heat and will fail in no time. Use proper alumin um tape to mate sections of duct. Support the duct at reasonable intervals . Keep your run as straight as possible, etc. etc.
According to FEMA, there are 2900 dryer fires reported every year, and the major contributor is lint. So the material used in your duct is very impor tant (i.e. Don't use PVC!!). Have you ever seen burn tests for those produc ts? Scary.

t but it too seemed kind of flimsey.
You probably won't find any structural dryer duct unless it's a custom job. Better off installing the standard "flimsy" duct and then using additiona l mechanical protection. Maybe box it in with 2x2? Nobody said it had to be pretty...
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On Tue, 15 Oct 2013 07:02:42 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Am I right that it should only be boxed in where he hits it, and the rest left open to radiate heat that isn't trapped inside a box???
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On Tuesday, October 15, 2013 10:38:37 AM UTC-4, micky wrote:

Good grief. They run dryer vents for 15 ft between the ceiling and the floor above in an enclosed bay and it apparently meets code. This heat stuff is a red herring. Dryer air isn't that hot.
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Plastic pipe is prohibited by codes as it is a fire danger. You should also avoid any kind of corregated pipe. The ridges reduce air flow and can trap lint becoming a potential fire hazard.
You should use rigid metal duct pipe. When you need to make a turn, try to use two 45 degree elbows instead of a sharp 90 degree elbow. This will improve air flow, so your dryer doesn't have to work as hard, and clothes will dry quicker.
Home Depot and Lowes both sell galvanized metal duct that works fine for dryer vents. It usually comes "unassembled", meaning you need to roll it into a circle and clip the seam so the sheet metal forms the 4" duct.
When you assemble the duct work, support it well every few feet with galvanized metal strapping. Slip the joints together, then wrap all of the joints with self adhesive metal foil tape. Don't use "duct tape", despite the name it won't hold up for duct work. Also, don't use screws to assemble the ducts as screws will catch lint creating a potential fire hazzard. My duct was only 5 feet long and I had a full roll of the foil tape, so I just wrapped the entire duct with the foil tape. Overkill, but I wasn't using the foil for anything else and it will ensure I have no leaks.
When you are installing the duct, make sure the joints are arranged "with" the flow. The air should flow from one section "into" the next section. You don't want it blowing into the gap between the two pipe sections.
If possible, you should see if you can reroute the duct so it is as short and as straight as possible. Maybe off to the side instead of straight ahead.
If needed, you can build some kind of protective frame around the ductwork. Just try to leave access in case you need to work on it later. In most cases this shouldn't be needed as you won't be going in your crawlspace all that often.
Good luck,
Anthony Watson www.watsondiy.com www.mountainsoftware.com
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