Master Bath Project

[GTPlumber]

Background:
We are planning to make some extra room for the master bathroom and are planning to remove the existing tub/shower combo to install instead a stand-up shower with a separate claw foot tub. I have decided to model everything in 3D instead of trying to figure it out in the crawl space. The existing drain system of the house is also ABS and I would like to stick with that. This also means that I must order my materials online as no local stores near me carry ABS anymore. This was another reason to go CAD first.

Below is the current plumbing:

(am I correct in thinking the drain for the current sink, which does have a vent stack, also vents the current toilet as a wet vent?)


Next, the proposed new layout:



The blue wet vent shown above is the drain coming off of a sink which is dry vented up.
The larger pipes are 3" pipes, the smaller ones are 2". I may reduce the p-traps down to 1-1/2, but I'll do that later if necessary or if you guys think so.

Questions:
My questions have to do with wet venting. I will be adding one additional drain and would like to avoid adding an additional vent stack if possible. According to the international plumbing code, I know that a horizontal wet vent is allowed. I've also had many discussions with plumbers stating that a water closet needs to be the most down stream connection of a wet vented system. Here are my questions:

1. What size does the dry vent need to be before it becomes a wet vent? (My understanding of the code is that the dry vent before becoming a wet vent needs to be sized for the largest pipe it will be venting as a wet vet. In this case it needs to be able to vent the 3" pipe for the toilet.)

2. Is the capacity of the vent (how many dfu) determined by the dry vent that leads to the wet vent or only the wet vent?

Finally I'll post a larger image of what I have mocked up following a picture of what it was previously. Please feel free to critique it and point out any mistakes I may have. I am not a plumber, even though my name says that idk why I picked that, but I am just figuring this out as I go so any help would be very much welcomed.

Old (I only roughly modeled this just to get it close to what is existing so it's not exact)

New

 

[GTPlumber]

My next question is can the large 3in vent used for the old shower also serve as the wet vent for the new tub? I ask because I could potentially leave the old sink connected like it already is and just conned the new tub to where the 3" line for the toilet turns. Is it UPC that says the water closet must be the most downstream fixture in a wet vent because I don't see it in the IPC.

 

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[Jeff H Young]

Is there a lav in that bathroom? it looks like a lav would be where the toilet partition is. trying to tell if the tubvent needs rolling up on 45 ? If its a lav it could be flat but with grade

 

[GTPlumber]

Is there a lav in that bathroom? it looks like a lav would be where the toilet partition is. trying to tell if the tubvent needs rolling up on 45 ? If its a lav it could be flat but with grade

Thanks for the reply. There is a lav in the bathroom. I've added a picture to indicate where it is.

I've also labeled where there is a 3" dry vent that turns into a wet vent. If IPC doesn't have anything requiring the toilet being the last fixture downstream, could I just connect the tub off of the end as shown in the following picture?

Thanks again.

 

[James Henry]

I would go with this one.

 

[GTPlumber]

I would go with this one.

Thanks for the reply. That's the one I'm leaning towards because the current lav drain line is sloped incorrectly and that would allow me to fix that issue (been like that since before I bought the house). You don't see any issues?

 

[James Henry]

does your lav vent connect to the 3" stack?

 

[GTPlumber]

does your lav vent connect to the 3" stack?

No it doesn't, it goes out the roof independently. But I did just go into the crawl space and the drain line from the lab is 1-1/2 instead of the 2 inch. I can change the wet vent part to 2 inch, but the dry vent part will still be 1-1/2 inch. Would this still be ok?

 

[James Henry]

Before I steer you wrong, is that 3" a "drain stack " or a "vent stack".

 

[GTPlumber]

Before I steer you wrong, is that 3" a "drain stack " or a "vent stack".

It's a vent stack.

 

[James Henry]

It's a vent stack.

I'm not so sure but it's your house. you can test it by removing the clean out cap and running some water up stairs. I would think that an inspector would let that short section of horizontal vent off the shower pass because the pipe is increased in size. if that 3" is a drain stack you can't wet vent fixtures (shower), that are NOT on the same floor. that being said, if it is a drain stack I would plumb it like I have sketched out to be safe.

 

[GTPlumber]

I'm not so sure but it's your house. you can test it by removing the clean out cap and running some water up stairs. I would think that an inspector would let that short section of horizontal vent off the shower pass because the pipe is increased in size. if that 3" is a drain stack you can't wet vent fixtures (shower), that are NOT on the same floor. that being said, if it is a drain stack I would plumb it like I have sketched out to be safe.

Thank you very much for all of your information! This is a single story house so it's definitely a vent stack. I just like to make extra sure what I'm doing is done properly.

 

[James Henry]

Then I would go with this picture. IPC approves an 1-1/2" vent in your situation. The shower vent needs to come off the drain at a 45 degree angle or better but because the vent starts out at 3" I would take my chances with the inspector. its your call.

 

[GTPlumber]

Then I would go with this picture. IPC approves an 1-1/2" vent in your situation. The shower vent needs to come off the drain at a 45 degree angle or better but because the vent starts out at 3" I would take my chances with the inspector. its your call.

Yeah I think I'm going to go this route. Than you very much for your help.