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We recently moved our dryer into the garage stacked on top of a washer. The easiest way to vent it was straight up about 6' into the attic, then a right turn in the attic 12' out the back of the house.

I had an appliance repair guy out to help with some propane connection issues and he said we shouldn't ever vent a dryer 'up' as it makes it a lot more likely to accumulate lint.

While I have no reason to doubt him, this also isn't something I had heard before. Coming from MN where most every house has the dryer in the basement and vents up, it seems perfectly normal to me.

In addition, prior to moving the dryer, it vented 'down' through our crawlspace and that was still caked with lint when I went to clean it out.

The question: Is it true that venting a dryer up causes more lint buildup and, if so, to what extent is it a greater problem than just venting horizontally or down?

I'm fine cleaning the vent once or twice a year and if that's what I'd have to clean any vent, regardless of direction it goes, I don't know that I want to spend the effort to re-route it underneath the house (which wouldn't be all that easy).

  • If this were true; as you mention, there'd be no way to install a dryer in a basement. – Tester101 Apr 10 '15 at 22:16
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    @DA01 (giving poor diceless a break from our comment thread and moving it up here) Given the illogic that has the laundry in the basement much of the time 60+ years past the age of servants, when most of it is generated on and stored when clean on the second floor, I think getting architects to do anything sensible (or homebuyers to buy a house that does not meet their outdated preconceptions that will ensure they need to move out to a nursing home a lot sooner than they otherwise might) is a lost cause unless you build it your dang self (which I'm dong, but that has it's own issues.) – Ecnerwal Apr 11 '15 at 0:30
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It really doesn't make any difference when it comes to lint build up. But you might consider putting a secondary lint trap near the dryer to help reduce the amount of lint trapped in the line.

  • I never thought of using a secondary trap. That's a good idea. Any particular type to look for? – DA01 Apr 10 '15 at 20:07
  • Main thing is to make sure that the section running 12 feet "horizontally" isn't. Treat it like a drain pipe and give it slope down towards the outside exit - also insulate around it - condensate, not lint. Lint does not care, all you can do for lint is to keep it as short as possible. Personally, I'd just plan on cleaning the pipe, since you'll have to anyway, rather than being too concerned about the secondary filter - it may help, it will also add back pressure (there's no free lunch) and reduce the airflow rate; and some lint still gets past, so you still need to clean the vent. – Ecnerwal Apr 10 '15 at 20:28
  • @Ecnerwal yea, I'm fine with cleaning. And with it in the attic, it's a whole lot easier to get to to clean than in the crawlspace. I did give it a slight down-slope towards the outside vent. – DA01 Apr 10 '15 at 22:34
  • (though...I do have to wonder why appliance manufacturers haven't come up with a better solution to the lint issue than the plastic screens in the dryer yet...) – DA01 Apr 10 '15 at 22:35
  • @DA01 I think it's actually a "hard problem" based on the amount I pull out of the 1/2-inch grid screen in my dryer that's after the fine-mesh screen filter, much less what gets past both of them to the pipe. Never using the flexible pipe is another bit of wisdom I think we all know (though I suppose it should be mentioned for the sake of any that don't.) Best setup I ever had was one that had a 2 foot vent - one elbow and a straight shot out the wall. – Ecnerwal Apr 10 '15 at 22:42
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As others have said going up is not a problem, it is the horizontal after that bites. Did you know that galvanized ducting can rust? Did you know that rusty pipe holds lint very well and is impossible to clean? Did you know that dryer lint can mold? Here is what I would do If I had to put that dryer back into service: brand new galvanized dryer duct for the vertical and lower elbow. ABS (not pvc) pipe from there on. Insulate nothing! Why? The vertical allows the heat to escape and the moisture that condenses there to run back into the dryer where it is re-evaporated. At this point the exhaust is cool enough not to melt the ABS which is versmooth and non stick to allow the remaining lint and moisture to leave without sticking to the pipe. Hindsight is indeed 20/20.

  • Who uses galvanized for dryers? That's what aluminum (rigid, not flex) is for. ABS will be lots of fun in the event of a lint fire. – Ecnerwal Apr 11 '15 at 0:31
  • Aluminum was not available, but it sounds like a great idea. – hildred Apr 11 '15 at 0:37

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