Hello,

I own a excavation company that installs water mains, services, storm, and sanitary pipe outside, my interior plumbing knowledge is lacking.

My new basement bathroom was just framed and I am getting ready to cut the slab.
I just wanted to get some opinions before I started cutting if this layout will work.

One concern is venting, I will probably have to use a AAV in the lav and am not sure if that is sufficient for venting the toilet and shower tub.

Another concern is after cutting the 4" existing cast and placing a WYE to service the bathroom the wye is pointing downhill of the bathroom drains. So I will be draining from the bathroom downhill to a wye and then back up to the existing cast drain pipe. This is hard to explain, I will add a picture.

Thanks and below are the pictures.

Proposed layout


Existing wet vent


Connection to existing cast iron, this is the WYE in question.

As long as the wye for the sink drain is within 72" of the tub trap, then technically an AAV under the cabinet will be sufficient to vent all three fixtures.

the rubber coupling used for the toilet "Y" are not allowed. must be sheilded.
i would change the "Y" for the tub and lav to a 45 and put the 3 x 2 "Y" next to it.

It is well within that.
Excellent thank you!

You>the rubber coupling used for the toilet "Y" are not allowed. must be sheilded.

Me>The rubber coupling is a 4" "fernco" made for joining cast to pvc.
Are you suggesting using a 4" no hub like this?

You>i would change the "Y" for the tub and lav to a 45 and put the 3 x 2 "Y" next to it.

Me> Not following...
I am using a 3x2x2 wye from the 3" main to the lav and tub.

sheilded couplings are required inside the house. all rubber are only allowed outside the house.
as for the 3 x 2 x 2 "Y".. i just like to see the shower draining straight into the "Y" with the branch of the "Y" rolled up to catch the sink and act as a vent. putting a 45 downstream of the "Y" does this.

Shielded couplings are NOT required in Michigan. Regular Ferncos are used all the time.

As far as the Wye is concerned, it MAY be a better setup the way Packy proposes, but again, there is nothing wrong with the way he has it. It is done that way all the time. I would actually go as far as saying plumbers around here almost never roll the wye up to the lav. It is all laid out on the same plain.

Thanks for all the advice.

So............is the one AAV going to be sufficient as a vent for the shower, toilet, and lav if I cannot connect to an existing vent?



Edited 1 times.

have a read here. you need an AAv good for 5 DFU..
[www.oatey.com]

Yes, the AAV will be suffiecient as long as it is large enough. Like packy said, it must be rated for 5 DFU's or larger. I typically use a 6 DFU Oatey AAV. I also only use them when I absolutely must, as a natural vent is a much better alternative.

Thanks!
I can hit a vent about 20' away in a unfinished room is that to long of a run to be effective?
I could also hole drill to the outside but the vent would be horizontal and exit from the side of my house by a dryer vent.



Edited 1 times.

The vent 20' away, if in fact it is just a vent, is the best option, but the AAV would be fine.

If I vent to the room 20' away do I still just vent the lav or do you vent each fixture?
Thanks again everyone!



Edited 1 times.

the venting arrangement is the same whether you use an AAV or plain old vent to a vent stack.