DWV Layout Help Needed

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LesP

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Hello and thanks in advance for checking out my "little" project! Here is the overall plan with dimensions:
BA Layout SM.jpg

I am moving two bathrooms from the South to the North side of the house. They will be back-to-back with a 2"x4" wet wall (non-bearing) between them. The joists (2"x10") run perpendicular to the wet wall but there is a full basement so access and altitude are not a problem.

Here is my first draft of the DWV based on my best understanding of UPC code:
DWV1 iso.jpg

A few questions:
- Is it appropriate to run 2" drain everywhere above Lav #1?
- Can the shower and tub revents be 1.5" so I don't have to butcher the wall studs
- I am planning to wet vent both toilets below all the other minor fixtures -- is there a better option?
- Could I use an AAV on Lav #2 in order to avoid another roof penetration?

Many thanks!
Les
 

Terry

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What you have drawn works.
Running 2" above the first lav near the toilets is good. For the far lav, you can get by with an AAV, but if you can tie in at the ceiling to the other vent, or make a second penetration it's better. They both work, but the AAV is work down the future when they need replacement. Sometimes you gotta do it though
 

LesP

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Thanks for the super fast response, Terry!

Unfortunately there is no attic space for tying the Lav #2 vent to the rest of the venting (it's 1965 construction with exposed car decking which serves as both the ceiling and roof!). Since there is a closet on the other side of the Lav #2 wall, would it be possible to put an access panel on the closet side (rather than behind the mirror above the sink)?

Here's the top view for the drain lines with the vertical studs shown (the joists below are basically aligned with the studs):
Drains Top View.jpg
My plan is to run the shower/tub trap arms and the master lav drain within the joist bays while running the toilet drains under the joists. This way I won't have to bore any holes in the joists. However, I will have to bore 2" holes (for the 1-1/2" portions of the venting) through 4 consecutive studs of this non-bearing wall. Alternatively, I could drill 2-1/2" holes (for the 2" drain lines) through the joists which would allow me to bring the revents closer together in the wet wall, but then the trap arms would be longer.

Which is the more efficient/effective/economical approach? Thanks for any suggestions on what will yield the best setup.
 

LesP

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I am getting ready to trek into the big city to buy all the parts for this project and would greatly appreciate it you clever folks can give my detailed plan the once-over. I will buy extras of everything, but it would be very helpful to know if I'm on the right track.

DWV rough.jpg

I understand that the UPC requires a cleanout for more than 135 degrees in direction change so does it work to put in a two-way fitting to head both up and down the line?

I will be tying into 4" hub & spigot cast iron at the end of the horizontal run. If I can remove the wye at the top and leave the hub intact, I figured I could use a service weight gasket with a 4"x3" adapter. Is this do-able (removing the lead & oakum?) or should I plan on cutting the hub off and using a mission coupling instead? By the way, all the plumbing above will be gone after the bathrooms are relocated.

Cast Iron Stack.jpg

Thanks, as always, for your input -- I have learned so much from this forum!
 

LesP

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Lots of views, but no additional feedback, so I hope you don't mind if I give this a little...bump
 

Mario's bro.

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Get rid of as many hubs as possible, then transition from there. From there you would have a 4x3 mission coup, 3" 90, 3" 45, 3" Y for your first cleanout. This Y serves as a cleanout and offset, another 45 and now you've got a straight run until the end, where you already have the end of the line cleanout.
I don't believe your water closets are vented correctly so that may be an issue.
 

Asktom

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The minimum clean out size for a 4" line is 3 1/2" (UPC), which doesn't happen in plastic, so you need a 4".
 

LesP

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Thanks everyone, for your comments!

Mario's bro: I believe the water closets can be wet vented as long as their traps connect downstream of the other fixtures (per UPC). I realize the drawing is hard to see, but I have the w.c.'s connecting below the 2" vent on Lav 1. Is this allowed/will it work?

Tom: the vertical portion of the drain is 4" cast iron and has a 4" cleanout at the base of the pipe. I'm planning to size the other cleanouts to match the pipe at that point (3" c.o. on the 3" portion of the drain, 2" on the 2" section). Is that the correct way to do it?
 

LesP

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I have reworked my DWV plan a bit and am still struggling with the correct venting for the two toilets.

Can they both be wet vented off the lav if I upsize the adjacent lav drain line to 3"? See M thru T on the drawing:

DWV v2.jpg

My Code Check book indicates that 2" and 2-1/2" pipe can only support up to 4 DFUs for horizontal wet vents, but 3" pipe can handle up to 8 DFUs. Am I applying this rule correctly?

Alternatively, could I insert a vertical tee-wye below point T and run a 2" dry vent up and over to join where the tub and lav vents converge? Would this effectively serve both toilets without one siphoning the other?
 
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