I am installing a mini washer/dryer into a second story bathroom. I want it to be the safest and easiest installation that I can do myself. I understand the basics: minimum 4" diameter tube. Use hard tubing not flexitube, No more than 25' and subtract 2.5' for each 90 deg bend, etc... But here are a couple questions about doing it right in my particular situation.

Most dryer venting systems are attached to the wall. In my case, there is already a conduit under the floor where I am laying pipe. The conduit is between a major beam and a 12" floor plank which will be under the bathroom floor. I want to run my dryer vent in that conduit. But access to the conduit will be on the floor. Can you do that?

The venting pipe will go into the garage attic, make a 90 deg bend and then go 10' to the nearest outside wall. The outside wall happens to be above the garage roof. The vent will exit on the second story about 2' above the surface of the garage roof. Is this acceptable? ( I see other cases where people vent dryers onto their roofs. I don't know if its a good practice.)

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    what is the size of the conduit and what is being used for now. If it is a plumbing vent, do not touch it. As far as venting a dryer onto a roof, not done usually. There may be a tenancy for lint and debris to collect around the vent, very unsightly. Commented Aug 3, 2011 at 10:57

1 Answer 1


If you have it too long with too many bends you will be creating a fire hazzard. You need to be able to clean out that dryer vent. If you have it running 15' one way and 10' another with 90 degree turns, then you might run into fire safty issues. If you can put it up against an outside wall, make your hole there on the second story. This will save you money, reduce fire risk greatly, and you wont have to pay a small fortune to have someone run a 30' snake to clean it every year.

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    Also, your dryer will dry faster with less energy if the vent is short/straight/smooth/open.
    – Jay Bazuzi
    Commented Aug 3, 2011 at 19:50

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