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Old 12-19-2012, 09:51 AM   #1
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Bathroom fan venting question


I need to vent my bathroom fan through my crawl space (15 feet wide). Im worried about the sloping of the duct, can you look at the attached picture and see if I'll be okay?
What worries me is that my upstairs bathrooms vents connect to roof vents. Sometimes the duct falls off of the vent and then its hanging in the attic. So the duct goes about 5 feet up, then 5 feet down (because there is a support halfway up). When this happens, I get water that runs back down and ends up on my bathroom ceiling. I was told this is because the line goes up then down. So now I'm worried about doing this in my basement.

BTW, I really don't have another choice. I *could* go through the basement wall, but the wall has ceramic tile all the way up to the ceiling and I really dont want to mess with cutting it out. I'd rather just go up and over the wall.

Thanks!

Bathroom fan venting question-basementfanillustration.jpg

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Old 12-19-2012, 10:33 AM   #2
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Bathroom fan venting question


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Originally Posted by gregsenne View Post
I need to vent my bathroom fan through my crawl space (15 feet wide). Im worried about the sloping of the duct, can you look at the attached picture and see if I'll be okay?
What worries me is that my upstairs bathrooms vents connect to roof vents. Sometimes the duct falls off of the vent and then its hanging in the attic. So the duct goes about 5 feet up, then 5 feet down (because there is a support halfway up). When this happens, I get water that runs back down and ends up on my bathroom ceiling. I was told this is because the line goes up then down. So now I'm worried about doing this in my basement.

BTW, I really don't have another choice. I *could* go through the basement wall, but the wall has ceramic tile all the way up to the ceiling and I really dont want to mess with cutting it out. I'd rather just go up and over the wall.

Thanks!

Attachment 62229
well you really don't have a choice...if you put a dip in exhaust piping ...it will collect water at some point...then what? ben sr

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Old 12-19-2012, 10:53 AM   #3
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Bathroom fan venting question


yeah i know I said I didn't really have a choice.. i guess I do I could cut through the tile, just really dont want to do that.
So my configuration will for sure collect water in the low spot that runs along all the joists? What if I insulate it, will it still hold water?
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Old 12-19-2012, 11:13 AM   #4
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Bathroom fan venting question


Nothing you do is going to top the water from pooling up inside the line if it's run that way.
Why can you not run it the other way between the joist?
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Old 12-19-2012, 11:26 AM   #5
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1. Why arent you running the vent pipe straight at us up in between the joists, and out the wall that would run parallel to the current pipe run?

2. If you have to run it as shown, why do you have to go back up and out through the band joist? Why cant you go through the foundation? Is it poured concrete? Just run 3 or 4 inch DWV PVC sloped at 1/8 inch per foot out to the wall, punch through. Grout in a steel nipple with epoxy cement, then go through with the PVC. Put a street L facing down on the end and put 1/4 inch screen in end to keep out creatures. Stuff backerod and sealant around pipe

corrugated flex is no good for this, as moisture will build up in the pipe.
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Old 12-19-2012, 12:06 PM   #6
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Bathroom fan venting question


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Why can you not run it the other way between the joist?
Because going one way would end up on the front of the house (which I don't want for cosmetic reasons), and going the other way would end up under the deck out back. And I'd really rather not vent the bathroom right under the deck where people sit so they have to smell bathroom odor! My drawing has it going out the side of the house where all the utilities are.



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2. If you have to run it as shown, why do you have to go back up and out through the band joist? Why cant you go through the foundation? Is it poured concrete? Just run 3 or 4 inch DWV PVC sloped at 1/8 inch per foot out to the wall, punch through. Grout in a steel nipple with epoxy cement, then go through with the PVC. Put a street L facing down on the end and put 1/4 inch screen in end to keep out creatures. Stuff backerod and sealant around pipe
It's cinder block wall, but there is only 3/4 of a block showing outside. That would put my vent in the ground, almost. So any snow would completely block the vent.

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corrugated flex is no good for this, as moisture will build up in the pipe.
Okay, metal or PVC pipe is fine with me. But am I still going to have a problem dipping down and back up if I use metal or PVC?

Thanks.
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Old 12-19-2012, 12:36 PM   #7
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Originally Posted by gregsenne View Post

..... and going the other way would end up under the deck out back. And I'd really rather not vent the bathroom right under the deck where people sit so they have to smell bathroom odor!
I'm curious what the experts say about this.

I'll be in the same situation when I finish our basement. I'm not worried about the odor as it will be infrequent and likely at a time when no one is on the deck. But my question is would moisture be an issue?
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Old 12-19-2012, 01:08 PM   #8
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I think the key here is how much moist warm air you are moving. If you have a shower in that bathroom it could be a lot of moisture. If not, not so much. I like PVC because it is solidly glued together, it is rigid, and it is plastic which is an insulator. Metal will leak at the joints. Maybe this does not matter in the crawl space? If not, just vent into the crawl space. (I assume it is vented?) if not vent out the front with PVC, paint it to match the house (Plastic Spray Paint after cutting the gloss) and plant a bush in front of it.

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Old 12-19-2012, 01:19 PM   #9
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The fan is directly above a shower. The crawl space is conditioned. Even if it wasn't, it's a code violation to vent to the crawl space. I like the idea of using PVC, and if I do, I will cut a hole in the tile to go straight through, (so I don't have the expense of 4" elbows). But, my biggest concern now is angling up to go out through the band joist. Since the PVC will hold the water in, the only place it could go is back towards the fan, and get all on the ceiling of the bathroom, which obviously would be the worst thing the water could do.

Is there any other option besides venting out front? I REALLY do NOT want to go out the front wall of my house
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Old 12-19-2012, 01:51 PM   #10
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Well Greg, what you can do is run the PVC out toward the wall, then install a reducing T just inside the wall with T down. Reduce to say 1.5 inch and run out block. Its easy to punch a hole in block, just hit a web. On main 4 inch run street L up, then back horizontal and out band joist with 4 inch. The condensed water will go down and out the T, and the air will go out the 4 inch vent. You dont need much slope at all with plastic, especially when its just carrying condensate. Different story with waste. I dont get your not wanting to buy fittings, they cost money, but not that much, and you are going to want to start right up against the joists near the fan. Hint: two 45's (1/8ths Bends) gives you a lot of flexibility to hit angles other than 90 degrees.
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Old 12-19-2012, 02:12 PM   #11
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Bathroom fan venting question


Just to make sure I got this right, here's what I pictured from your response:
Bathroom fan venting question-fanillustration.png

the green I added in the picture is the ground.
Is there any issue using the bottom example? I would still prefer this option, but the top example is fine too.
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Old 12-19-2012, 02:18 PM   #12
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Bathroom fan venting question


Or, what if I put the Tee in the middle of the wall, and run the 1.5" down the basement wall and tie it into the bathroom plumbing?
This would actually be my favorite solution, if this is possible. I would put a trap on the 1/5" line too that way I can't constantly smell my septic tank from the outside vent.

Bathroom fan venting question-fanillustration.png
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Old 12-19-2012, 02:46 PM   #13
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Hi Greg,

It concerns me that the trap might dry out, but I like your idea. Mine was more like as I show below because it will be difficult to reduce all the way fro 4 inch to about 1 inch. I think it will work either way.
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File Type: pdf Gregvent.pdf (16.8 KB, 54 views)
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Last edited by jagans; 12-19-2012 at 02:55 PM.
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Old 12-19-2012, 04:01 PM   #14
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Bathroom fan venting question


Okay, thanks for the help! I think I might go with this solution.

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