Installing vent for basement bathroom

Old 12-29-16, 09:40 PM
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Installing vent for basement bathroom

I am in the process of finishing out my basement including the addition of a bathroom.

I am trying to figure out the best way to vent the bathroom exhaust fan. I currently have a dryer duct that is no longer in use, that runs along the sub floor (ceiling of the basement) and vents to the side of the house. I am thinking to re-purpose that existing duct and simply extend it slightly to reach the bathroom exhaust fan.

I have a couple of questions / concerns:
1. The dryer duct is larger than what generally required for the bathroom exhaust fan. Is that an issue?
2. I am running approximately 13 feet horizontally to reach the side of the house. I would anticipate there would condensation along that length. Should I be concerned that the current duct was not intended to be water-proof?
3. If the current duct is not sufficient, any suggestions as to the best solution? Would it make sense to use the same route and replace the dryer duct with pvc or abs piping?
4. Does this duct / piping specifically need to slope towards its external vent?
5. It is also possible for me to run piping from the basement through into the garage and vent through the roof, but that seems like a lot of unnecessary work when there is already a route in place.

I am also not up to speed with what restrictions there may be from a code perspective.

Any help would be appreciated!
Old 12-30-16, 02:40 AM
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Welcome to the forums!

1) Being larger in size will mean a transition, and should not affect air movement. It will just slow down when it reaches the larger pipe.
2) Your ducting should be hard pipe and ideally insulated. Corrugated pipe has too many ridges and can sag causing the P trap effect if enough water accumulates.
3) I would use metal ducting pipe. Lighter and you can insulate it.
4) From a bathroom the air movement itself should assist in dissipating moisture. I doubt you can get a slope sufficient to run water, and there won't be that much accumulation unless you give it reason to (see 2)
5) I would not run a pipe up through an existing non-leaking roof. Penetrating that roof only gives a chance for water to leak. Since you have the existing un used dryer vent....use it.
Old 12-30-16, 03:28 PM
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Does the bathroom have a shower/tub or just a commode?

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