Dryer vent elbow joint sealing

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New Member
Jan 8, 2024
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New York

We have a dryer vent in our apartment that has a couple of twists and turns due to the design of the floor plan, on its way out to the roof to vent. The twists have been done by elbow joints covered by aluminum tape.

Unfortunately, due to the cold temperatures outside, the hot, moist air in the vent leaks out through the elbow joints and creates condensation drips (which pool and leak over a period of time when the dryer is in operation).

(Re-routing the vents to keep them straight is not an option because of the design of the house)

What are some options to completely seal the vent, and specifically the elbow joints?
1) Is there any sealant that can be applied on the outside for waterproofing to prevent the condensation leak?
2) Is there "better tape" (other than typical aluminum tape) that can do the sealing?
3) If the elbow joint needs to be replaced, is there any product that can create a good seal?

Thanks in advance for your help!
You live in a cold area and what is happening as I’m sure you understand is the moisture rich exhaust from the dryer is condensing before it makes it out of the building. You now have trapped water in a duct only intended to carry gas not liquid. Sealing it up will not really solve the problem because as much as you don’t want dripping water you also don’t want ductwork holding water. If the duct is traveling thru a cold attic space that would quickly condense the water out and it could then run backwards/downhill and collect in this low place.

Do you find it works better in the summer than winter?

Without knowing if there is a shorter path to outside that could be used and the layout and length of the total run now and where it travels thru on its way out it is hard to over additional advice.
Folks get inventive.
I ran into a fellow in BIG BEAR, CA, who had a similar situation. In the winter he'd disconnect the external vent, and connect it to a 3', 4" galv. pipe, lined with swamp-cooler screen, with a fine mesh GENI vacuum cleaner filter at the end. He said he only changed it twice a season and the dust was not unusual but was going to double the GENI filter next season.
@Snoonyb makes a great point about a DIY winter indoor diversion. Most of the time depending on where you live and what type of heating system your home has the house can use extra moisture in the winter.

If DIY is not your thing they sell indoor dryer vent kits. It would require switching out fall and spring though.

Ace 4 in. W X 4 in. L White Plastic Lint Trap - Ace Hardware

Amazon also has several also.
First, check all of the piping for lint build up. A partial restriction can slow the exit enough to cause condensation.

Second, if this is a cold weather "winter only" problem, check for hoarfrost closure or snow/ice closure on the roof.

If insulating the duct, as Sparky617 suggested, does not fully solve the problem, a Dryer Vent Booster Fan will.
Check about them here: What's a Dryer Vent Booster Fan and Does It Really Work? (They are not all as large and unattractive as the one pictured in the article.)
Make certain there are no leaks in the attic or the fan will blow flammable lint all over the place.

If you want to seal the joints, low VOC water based Duct Mastics are available that are not flammable & won't melt off.

I second what SlownSteady said about venting gas dryers in the house. Carbon monoxide is present in exhaust gas, as can be un-burned fuel gas. It's a really dangerous plan.