DWV Layout, especially venting

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Whale

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Hi, I am getting rid of the cast iron drains from 1924. Please take a look at what I am planning to do and let me know what you think about the venting etc. On the main floor is a small bathroom, a washing machine, and a kitchen sink. Presently all these fixtures are draining through a main, 4" stack, in the basement, which is also a vent for all the fixtures except the kitchen sink which has it's own vent.


The main stack presently is a straight vertical shot from the roof to where it makes a 90 and leaves the foundation in the basement. I need to change where the main stack is exiting the foundation so it can be connected with the new buried outside sewer line.


Once the cast pipes are removed I will be left with the main stack, coming from the roof, entering the basement, and now that will be used as a 4" vent. I will then need to run a new 4" horizontal main house drain to where it will eventually drop down and turn and exit the foundation.

I have flexibility how I can run the old 4" vent pipe once it enters the basement and also how to run all the branches, to connect with the new horizontal 4" main drain, or even connect branches together. I was planning on running all branches from the fixtures with 2" pipe. The main thing I am concerned about is the proper venting. I can't do anything to run new vents in the walls and there is no attic. I would rather not use AAV valves if it can be done without them. It seems like there will be wet venting. I have a few diagrams of different ways I thought to do it. Please let me know if any will work or any improved ways of doing this. thanks.


Diag A seems like I would need to use an AAV valve?
Diag B I moved where the 4" vent connects with 4" main drain.
Diag C moved where WC connects with 4" main drain.
Diag D moved WC to another location where it connects with 4" main drain.
 

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Jeff H Young

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You can do it like drawing a except need vents or aav at washer and lav plus the tub would be differant youve got it as 4 inch main so for tub eliminate what you have and iunstead put a 4x4x1 1/2 san tee above the 4 inch longsweep 90 the santee will provide trap arm for tub and vent out the top through roof
 

Whale

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You can do it like drawing a except need vents or aav at washer and lav plus the tub would be differant youve got it as 4 inch main so for tub eliminate what you have and iunstead put a 4x4x1 1/2 san tee above the 4 inch longsweep 90 the santee will provide trap arm for tub and vent out the top through roof
Thanks for the response Jeff. Do you see any other way to do this without aav vents. Do you think diagram B could be modified in any way as not to need the aav or at least one of them?
 

Jeff H Young

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Sorry I dont see a way around having a vent of sorts coming off above the p trap on both the washer and lavatory.
The AAV is easy and saves opening up walls , anymore than you already need.
 

Whale

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Sorry I dont see a way around having a vent of sorts coming off above the p trap on both the washer and lavatory.
The AAV is easy and saves opening up walls , anymore than you already need.
The bathroom sink and the washing machine drain are only 16 inches apart. there is a wall between them. Could I just use one AAV valve for both two inch drains and place the AAV in the washer room?
 

Jeff H Young

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as long as the vents are connected need a 16 inch piece at least 6 inches above overflow of the washingmachine. otherwise its illegal and a bad job
 

Whale

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as long as the vents are connected need a 16 inch piece at least 6 inches above overflow of the washingmachine. otherwise its illegal and a bad job
Thanks, what would be the overflow of the washing machine, where the drain tube exits the machine, the top of the stand pipe where the drain tube enters or?
 
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