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Old 12-10-2012, 04:12 PM   #1
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vent under eave vs puncturing roof


I have a stand alone 8x10 bathroom out on a ranch in an area that is often but not always windy. Let's say I need to add a new vent for the toilet. What is the value added of puncturing through the roof compared to just ending it under the eave? Is that extra foot or two of height going to save me from smelling the gasses?

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Old 12-10-2012, 04:17 PM   #2
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I have a stand alone 8x10 bathroom out on a ranch in an area that is often but not always windy. Let's say I need to add a new vent for the toilet. What is the value added of puncturing through the roof compared to just ending it under the eave? Is that extra foot or two of height going to save me from smelling the gasses?
not sure where your located...but its code to exit out roof.... yes you can and will get sewer gas if you put under eave...ben sr

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Old 12-10-2012, 04:31 PM   #3
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not sure where your located...but its code to exit out roof.... yes you can and will get sewer gas if you put under eave...ben sr
As long as I don't announce that it's a bathroom the county will not do anything about it. Don't need to register or ask permission to build anything I want under 120 sq. ft. The bathroom is 8x10.

Will it matter that much that I puncture the eave and extend another foot above the roof? The eave is out in the open and not near any windows or doors.
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Old 12-10-2012, 04:43 PM   #4
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vent under eave vs puncturing roof


Get puncturing the eave out of your mind.

Is there not anywhere in the basement that you can tie into?

If not, check with your building permit department to see if Air Admittance Valves (AAV) are allowed by code.

Please do this under permit. Building inspectors are not that bad (usually). It will make resale a lot easier.

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Old 12-10-2012, 11:14 PM   #5
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vent under eave vs puncturing roof


What is with all these half-cocked hairbrained ideas? Why even ask if your response is going to be : "the county won't do anything about it if i dont announce that it's a bathroom"

Sure, you are 100% correct.

If you want the professional opinion that you came here to get :

Plumbing code requires vent termination to occur in certain places. Under an eave is not one of them.

However : I figure you're just going to do it your way in the end anyway.
Best wishes and happy holidays.
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Old 12-10-2012, 11:21 PM   #6
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vent under eave vs puncturing roof


Its a lot easier to get airflow over the vent which makes it easier to draw air into vent when it comes up through roof line.
Don't forget to increase to 4" a foot below the roofline to keep it from frosting over if you live in a cold area
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Old 12-11-2012, 10:10 AM   #7
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If the roof is vented your going to just sucking in the sewer gases into the attic by doing it the way your suggesting.
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Old 12-11-2012, 10:42 AM   #8
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vent under eave vs puncturing roof


There is a real good reason not to go through the eave. Now it is going to bother me all day because I can not remember. It will not vent right, the gas can bellow back down right into a window. You could try and not vent everything and see how that works for you.
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Old 12-11-2012, 11:17 AM   #9
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In order for the gas to be sucked out of the vent there needs to be air pasing over it to create a negative pressure. It's called a venturi.
http://library.thinkquest.org/C01220...turiEffect.htm

Same thing happens with a chimmney.
http://library.thinkquest.org/C01220...turiEffect.htm
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Old 12-11-2012, 11:42 AM   #10
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vent under eave vs puncturing roof


The National Plumbing code, and the National Electric Code, and most other codes have developed over the years in response to what works and what does not work vis a vis life safety. They were not developed by a bunch of building inspectors sitting around a table thinking of ways to mess with homeowners. If anything, some of the codes are not stringent enough, because they are consensus codes, driven by cost. Since installing a vent through a roof is a fairly easy and reasonably priced thing to accomplish, what is your point?

Last edited by jagans; 12-11-2012 at 11:49 AM.
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Old 12-11-2012, 01:04 PM   #11
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If the roof is vented your going to just sucking in the sewer gases into the attic by doing it the way your suggesting.
Not a chance. The eave is sealed off with trim, caulking, and several caked on layers of paint. More often than not the ranch is windy. It's between two mountain ranges. Air moves around alot out there. It's a wide open area.
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Old 12-11-2012, 01:22 PM   #12
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what is your point?
I'm not trying to make a point. I'm simply measuring twice before cutting once.
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Old 12-11-2012, 02:02 PM   #13
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vis a vis life safety
Please elaborate. Two problems come to mind. Is the gas explosive? If I turn on the light switch can that cause an explosion? Is the gas suffocating? Can somebody pass out or die from lack of oxygen?

I'm asking because I want to know how concerned I should be not so much from the vent going through the roof but from leaky plumbing. Let's say the wax from a toilet seal is not set right and gas will leak out.
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Old 12-11-2012, 02:49 PM   #14
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Please elaborate. Two problems come to mind. Is the gas explosive? If I turn on the light switch can that cause an explosion? Is the gas suffocating? Can somebody pass out or die from lack of oxygen?

I'm asking because I want to know how concerned I should be not so much from the vent going through the roof but from leaky plumbing. Let's say the wax from a toilet seal is not set right and gas will leak out.
I think the stink would drive you out of the house before it ever concentrated enough to kill you.

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Old 12-11-2012, 05:39 PM   #15
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vent under eave vs puncturing roof


If the wax seal loses integrity it will smell in your bathroom letting you know you have a problem. You will also have water on the floor when you flush in most cases.

If the vent is run out through the roof, air passing over the pipe draws the gas out (Bernoulli?, High Velocity= Low Pressure?) if you point the vent down in the eaves, air hitting the wall below will flow upward and force backpressure on the vent, thereby forcing more methane into your home and out the broken seal

The gas is methane, and yes it is flammable and potentially explosive, but I doubt that this will happen. Go ahead and try it if you want. Do you smoke?


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