bathroom vent stacks

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  #1  
Old 06-17-03, 08:22 AM
azsteve-o
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Question bathroom vent stacks

I'm in the process of a bathroom remodel. Currently our bathroom has two vent stacks extending through the roof. Is there any reason why I cannot join those stacks in the attic space and have just one stack coming out of the roof?

Does the main stack extending through the roof need to be a 3" stack because it vents the toilet, or can it transition from a 3" in the wall to a 2" in the attic?
 
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  #2  
Old 06-17-03, 08:58 AM
Ed G
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No you can not go from a 3" vent to a 2" vent. This would result in a smaller vent and the fixtures would not drain properly. You could combine the two vents provided that they are in the same area, but you would have to resize it so that the combined vent is the correct size. Why do you want to do this?
 
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Old 06-17-03, 11:21 AM
azsteve-o
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Cool

I am doubling the size of our very small 1950's master bath and therefore have to redo the entire water supply system and DWV system. I have already removed the toilet and the 3" vent because I needed to remove that wall to enlarge the bathroom. The 2" vent is located in a wall that is remaining. Keeping it a 2" vent would just have allowed me to keep the same roof flange . I will change it out to a 3" vent. Thanks for the advice.
 
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Old 06-17-03, 03:14 PM
Ed G
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Well now it may not be that simple. See if you are going to marry the 2 inch and the three inch into one three inch, you need to make sure that the 3" is sized to accomadte all the fixtures of both vents. Please list the fixtures you have in the house, # of sinks, toilets, laundry, etc..
 
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Old 06-17-03, 03:19 PM
Ed G
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Also what size is your main, if you have a four inch main and no other vents than a 3" would not be to code, it may work, but it wouldn't be to code. the total cross sectional size of all vents must be greater than or equal to the sewer system it serves. So if you have a 4"main than you would need a 4" vent.
 
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Old 06-17-03, 03:48 PM
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What is the mainline size, and when you look on the roof, how many of each size pipe do you see protruding out it?
 
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Old 06-17-03, 03:53 PM
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For the record, our code was updated in 2000 to allow for smaller vents.... In fact, we only have to have a single open air vent at least HALF the size of the main... So in your case, it would be code to tie in the 2" to the 3" and then reduce both of them to 2" before going out of the roof, and it is certainly functional...
 
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Old 06-17-03, 04:08 PM
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I would think we would want to know where he lives, if he lives in the area uder UPC then, he should follow these codes. Right now we have no idea where he lives, so we can't just say, you can do it this way or that way.
 
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Old 06-17-03, 04:12 PM
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If you live in a very cold part of the country, you do not want to reduce your venting. Vents can freeze over (due to hoar frost) and cause problems.

just a thought...hey good luck with your project, sounds like you got a plan...
 
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Old 06-17-03, 04:33 PM
Ed G
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Ragnar I am fairly certain the code says you must have at least 1/2 the size of the drain for the vent, but that the total needs to equal the drain. I will look it up Tomorrow and site the code numbers from the UPC. Who knows I might be wrong.
 
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Old 06-18-03, 08:28 AM
azsteve-o
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I live in Phoenix, AZ so freezing temps are not a problem (I can only wish). My main is 4".
In addition to the 2" and 3" vents in the master bath, I have coming out of the roof a 2" vent for the laundry, a 2" vent for the main bath and another 2" vent for the kitchen. The reason I ask the question is because the main bath is a full bath and only has one 2" vent.
It would certainly be easier if I could tie the 2" and 3" together in the attic and then go through the roof with a 2", but the last thing I want to do is to have to redo it later because it doesn't function adequately.
Thanks for all the great responses.
 
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Old 06-18-03, 09:10 AM
Ed G
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Just for clarification Chapter 9 Vents. Section 904.1 The size of the vent piping shall be determined from it's length and the total number of fixture units connected therto, as set forth in table 7-5. The diameter of an individual vent shall not be less than 1 1/4" nor less than half the diameter of the drain to which it is connected. In addition, the drainage piping of each building and each connection to a public sewer or a private sewage disposal system shall be vented by menas of one or more vent pipes, The aggreagate cross sectional area of which shall not be less than that of the largest required building sewer, as determined from table 7-5.

At any rate you would be fine to run a 3" vent. You may function on a two inch vent, but code requires any vent with a water closet (toilet) or six trap fixtures to be on a minimum 3" vent.
 
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Old 06-18-03, 02:56 PM
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Sent 2 " out the roof, you won't have any problems. Your private use toilet is from 3 to 4 fixture units, it is higher if it's public use.

My book says 2" min on a toilet.
 
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Old 06-18-03, 05:04 PM
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Just wanted to mention the frost thing.

In just looking at a few things, you fall under the Uniform Plumbing Code with AZ stipulations.

Plumber2000 is right on track, but I'd put in a 3" as Ed G said. Not to be politically correct, but code varies so much from jurisdiction to jurisdiction. What is perfectally legal and safe here can be bad news for someone else.

When in doubt, call your local building code inspectors and ask questions. You can always give them your neighbors name....

Good luck...
 
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Old 06-21-03, 01:00 AM
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Last edited by twelvepole; 06-21-03 at 08:14 AM.
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