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Discussion Starter · #1 ·
I have a gas dryer that vents through a duct with the effective length of 47 foot.


(90 degree then 8ft vertical right from the dryer; 90 degree then 21ft across the basement ceiling; 90 degree horizontal then 2ft along the wall; another 90 degree and 1ft to the outside)


At the two 90 degree turns, where the vent also is routed 1 vertical foot upwards in order to clear the basement wall sill, dryer condensation seems to collect and drip out. I did clean out the vent but it seems to be a reoccurring issue.


I'm in the process of setting up a workbench under the vent where it drips with some expensive electronic equipment. I don't really have a better place for the work bench. So I really would like to get a handle on the dripping issue.


A solution is to build a "roof" over the bench that catches any dripping and collects or routes the water away. But I'm wondering if there are better solutions.


How much would adding a dryer vent blower help? I'm aware the length is on the long side and that the blower would help the performance of the dryer. But would it also guarantee that no condensation and dripping from the dryer vent occurs, especially since there are still the two turns and it goes up a bit? My gut feeling is that it isn't good enough for that.


Another idea that came to mind is to eliminate the last two turns and go straight through the concrete foundation above the basement window. See green dot on photo for proposed location. The duck would vent right above the basement window. The basement window is in a window well. This would conflict with the 3' suggested?/code? distance of any opening. However, I rarely open the window currently and don't anticipate to open the window often in the future either. The added benefit for that suggested routing is that I can make the duct slope down, so any dryer condensation water will run to the outside.


What do you think of the dryer vent rerouting. Will it cause issues venting right above the window well/window? Should I reroute and add a booster blower? Is a booster blower by itself enough?


Thanks for your help and insights.
 

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retired framer
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There should be lots, of rebar to build the bridge over the window so might not be the best idea and then you should change the window out for a none open window.



Maybe if you add a booster fan about half way and change the last half of the pipe to pvc with sweeping corners
 

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I wouldn't add any unapproved booster fan to a gas dryer, could void insurance if something happens and cause operational problems.

Could even mess up fuel to air mix. If it fails without an interlock and interferes with flow, could be a major hazard.

Which duct is for the drier? metal or the insulated flex?

There will be specific guidelines for venting you must follow.

Condensation is caused by having the exhaust cool off too much - low velocity or (if insulated) duct needs insulation if run is too long and going through a colder space.
 

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retired framer
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Because it's hard to cut through or due to structural concerns?

Why that?

One solid window would bring into code.


I don't know if a coring bit would notice the difference with steel??

As far a strength, it's a crap shoot at where the steel is but the floor jousts above are going the right way so you could just add a matching length of LVL 6 inches longer than the window is wide, that is what we do instead of a header or that concrete BS.
 

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it may not be approved for your machine, be careful.

if your dryer is vented in accordance with instructions, you shouldn't be getting condensation unless the basement is cold.

Make sure the pipe is completely clear of lint and the correct size, within the length requirements.
 

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Discussion Starter · #9 ·
One solid window would bring into code.


I don't know if a coring bit would notice the difference with steel??

As far a strength, it's a crap shoot at where the steel is but the floor jousts above are going the right way so you could just add a matching length of LVL 6 inches longer than the window is wide, that is what we do instead of a header or that concrete BS.

What is a LVL?
 

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Discussion Starter · #11 ·
If we have to bring out the code book then it's already not according to the IRC or the installation instruction of the dryer, even to 2000 code. The exhaust vent is to long according to both of them. That was a professional installation which I haven't touched so far.


My personal opinion is that having a bad vent run is worse than having the vent next to a window that no sensible human would open while drying, even with the current location of the vent.



Current: https://codes.iccsafe.org/content/IRC2018/chapter-15-exhaust-systems
At construction/installation: https://codes.iccsafe.org/content/chapter/13867/
 

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Can you find some non-flammable duct wrap insulation to stop the condensation?

*

As much as i hate electric resistance heat - an electric dryer may be the best option in your case. There are fewer venting restrictions and no co risk.

Exhaust from a gas unit can actually have more moisture than electric because steam is a byproduct of combustion.
 

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You'll still want to wrap it with insulation.

Dryer dicts are considered "moisture exhaust ducts" in our code. All of the code is based around handling the lint problem, as the exhaust products are so diluted they are barely measurable.

As for the booster fan, it'll get caked with lint in no time. I actually take care of a building with an exhaust fan engineered for this and they still use a secondary lint trap before the fan. (after the one built into the dryer.) we still need to clean the fan and the outside grill every few years.

Cheers!
 

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So coming back to rerouting the dryer vent to exit above the window isn't something you would recommend then?
Insulate the pipe and you'll see a marked improvement. You can also seal that particular joint to help.

Going out the wall will reduce the condensation in the vertical 1ft, but not the rest of it running back to the dryer. It won't hurt, as long as it's well above the snow line.

Cheers!
 

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You're effectively at 52' of vent pipe with all those 90degs when you should be at 35.

Can you head left from that pic and go up into the joist bays and out through the rim joist there, much closer to the dryer?
it seems you need to cut some of the 90s as well as the length out of the equation. I'm no expert here, so I don't know how much you can cheat the 35' rule. Are all joints taped nicely with AL tape?
as mentoined, the water is condensation from this cooling off before exiting. I'm not sure if insulation will solve the problem either, but it would help.
 
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