A stacked washer dryer is to be retrofitted. The electric dryer is to be mounted on top. The wall behind the stack will be drilled so that a 4" dryer vent can be installed and vapor can be vented outdoors.

There are 3 sites for drilling the exhaust hole to outdoors:

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Site 1: has a disadvantage of height and proximity to electrical wiring and proximity to wooden steps. The washer dryer pair is to be installed on the other side (inside) of the wall.

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Site 2: has the advantage of being within 10 feet of the washer dryer, however, the brand new HVAC equipment is nearby underneath.

Site 3: has the advantage of no equipment located overhead / underneath. The disadvantage is that it is the duct would be approximately 20 feet.

I am leaning towards / prefer site 3 as it is away from equipment. The manufacture recommends that the duct be metallic and under 7 feet.

Is there any precedence for a 20 foot duct? What if any problems should I anticipate if site 3 is chosen?

  • duplicate posting; other posting has attracted a number of comments and should be the one kept.
    – Armand
    Aug 15, 2022 at 21:22
  • Page 15 of your manual states 41 feet with 3 elbows. How do you get a 7 feet limit?
    – Solar Mike
    Aug 16, 2022 at 6:01
  • Everyone should be aware of this version of the question and the commentary on it. (VtC that version as it is, essentially, the same as this one, but doesn't have answers.)
    – FreeMan
    Aug 16, 2022 at 15:17

2 Answers 2


I would use site 1. There is nothing wrong with venting the dryer there other than the fact that you might feel warm air when you walk across the landing. There is no issue with proximity to electric or A/C- it is simply warm air being exhausted.

I would make the shortest run possible and try and avoid the vent pipe having to go up vertical. The biggest consideration should be avoiding any lint that the dryer's lint screen misses accumulating in the vent piping.

  • 1
    One reason not to use #1 would be if this is in an area that gets snow. The hot dryer exhaust will melt it and then when the dryer stops it will freeze into nice slippery ice on your stairs.
    – nobody
    Aug 16, 2022 at 0:09

site 1 continue the duct under the landing and terminate it flush with the edge of the landing.

site 2 it's above the AC, it'll do no harm there, warm damp air rises.

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