Back to Back Bathroom DWV plumbing diagram. Please give me your opinions.

[MG70]

My house is a 1970's prefab, 2 level house, on well and septic, and all the DWV plumbing is concentrated along the rear wall of the house in the unfinished portion of the basement. Current plumbing uses (black) ABS pipe and I'm planning on sticking with the same for practicality. The ABS connects to an iron pipe before exiting to the septic system approximately 52" above the basement slab floor. Local plumbing code is 2018 IPC.

I'm converting one larger bathroom into Two smaller Back to Back Bathrooms each measuring 8' L X 5' Wide, separated by a 2X4 wall in which I plan to run the plumbing. Each Bathroom will include a sink, toilet, and shower, in that order as you walk in and the back wall will incorporate a small sliding window in the tiled shower surround.

I've done some research on the system design and correct fittings and subsequently decided to separate the toilet drains into separate fittings and change the separation wall from a 2X6 to a 2X4, in addition to being flexible about the stud spacing not having to be 16" on center since none of the walls in question are load bearing. I also discovered that the house has what seems to be a long "whole house vent", the horizontal part of which I intend to use for my kitchen drain in the future.

I'm posting here so that more experienced people can comment on my plans and hopefully make helpful suggestions. I've been very lucky with previous replies to my posts about well water and the use of Pex for replacing copper.

Thanks in advance and I hope everyone has a relaxing and safe weekend!

 

[Reach4]

At lavs, use a double fixture fitting.

At shower drains, do not use what you propose; use two wyes. All lines joining will be via wyes.

https://wabo.memberclicks.net/assets/pdfs/Plumbing_Venting_Brochure_2018.pdf page 12 bottom is a big wet vent diagram that services two bathrooms.

 

[Sponsor]

 

[MG70]

Reach4, as usual, you're the first to offer assistance!

I'll change the fittings in question in my shopping cart and study the pdf linked. I'll also search for a free software that'll allow me to work on pdf scans so the next diagram is of better quality. I'm sorry for how bad that jpeg scan turned out.

Thanks and I hope you have a safe weekend!

 

[MG70]

I re-drew my plans and changed my fitting selection. Even though in the drawing the vent lines run high along the wall, I plan on keeping them low until connecting above the lavatories Double Fixture fitting in order to minimize the chances of punctures from wall shelving, mirrors, light fixtures, etc.

1. Can someone more experienced please glance over the fitting selections to see if there are better options?

2. After having read the Wabo plumbing vent brochure provided by Reach4 above, thank you, I'm not sure whether the dry vent stack in the center is needed. Can anyone comment?

Notes:
The rightmost vent stack is wet vented from the lavs down.

There's currently no kitchen. I estimate the kitchen sink and dishwasher (both which will vent through the leftmost dry vent stack) to be installed within 17' of the base of the main vent stack which corresponds with the Lavatories. Ceiling height is a little less then 8' and the roof line is also low (there's a basement, but not other floor above the main).

3. Would it be better to move the center dry vent stack to the right (upstream) of the toilets?

4. Does anyone have any suggestions for a durable, leak proof, roof vent boot and cap or whatever you call it? The roof is from 2023 and I have some spare shingles.


Lavatories/Sinks
(HD, Lowes, and Amazon don't seem to have 1 1/2 to 2" double fixture tees). Look elsewhere...
or buy
(1) 2" DWV Double fixture Fitting
(2) 2 to 1 1/2" reducer (for 1 1/2 P-traps)
(2) 1 1/2" P traps with solvent weld available at Lowes
+ (2) eventually buy sink tail piece adapter once those are sorted.
(1) 3" X 2" Long turn tee wye with cleanout and cap/plug
(1) 3" ABS FPT adapter (cleanout)
(1) 3' MPT Plug (cleanout)
Cleanout may not work because it would be too close to a wall. Vanity size comes last.
(3+) ABS 2"X 5' pipe for vents
+ 2" pipe to run up the wall to connect with other vent stacks
Lowes only has 2' and 5' lengths but nothing in stock! HD has no 2" ABS pipe. Should stick with ABS or switch to PVC or use the 50 year old ABS for dry venting?

WC/Toilets
(2) Toilet Flange, 3" ABS stainless steel closet flange (should slip outside 3" drain pipe)
(2) 3" 90 hub
(2) 3" 45 hub to street (to connect to wye)
(2) 3" wye hubs

Showers
(2) drains for shower bases (check size, look for white ABS, or use pvc w/proper solvent)
(2) 2" p traps with solvent weld
(2) 2" 45 street elbow
(2) 3X2 wye hubs

Venting
(1) 2"X2" ABS DWV 90 elbow (left, uppermost dry vent stack comes from kitchen, not pictured)
(1) 2" ABS DWV sanitary tee (mid-section uppermost dry vent stack between toilets and showers)
(1) 2" ABS DWV sanitary tee (upper dry vent connecting to rightmost dry vent stack from lavs)
(1) 3" X 2" Long turn tee wye (mid-section lower wet vent between toilets and showers)
(1) 2" ABS DWV coupler (dry vent to dry vent from kitchen to bathrooms)

 

[Reach4]

1. Is pipe ABC horizontal in the attic, and have no connection to NM ?
2. is pipe coming in at N horizontal delivering waste from the kitchen?
3. M, L ,K, and J are combos or a (wye+a 45) or a wye only.
4. If IPC, pipe DE would not be needed I think.
5. H would be a 2 inch longs sweep feeding into a 2 inch to 3 inch adapter

 

[MG70]

1. Is pipe ABC horizontal in the attic, and have no connection to NM ?
A: My drawing is supposed to be the wall separating both bathrooms. I'm planning to run ABC vertically through the wall separating both bathrooms.
I'm planning to run CDF horizontally at a slight angle, connecting to G, right above it. F will very close to G
ABC does Not connect to NM

2. is pipe coming in at N horizontal delivering waste from the kitchen?
A: Waste from Kitchen connects to the same Pipe at N, the main waste stack, however below N. It's existing plumbing. I'll have to modify it so that NM drains into it.

3. M, L ,K, and J are combos or a (wye+a 45) or a wye only.
A: I have them as Wye + 45 but maybe I'll also buy 4 combos and see what fits better. Thank you.

4. If IPC, pipe DE would not be needed I think.
A: 2018 IPC w/local county amendments. I remember reading something about the incremental benefit of such an additional dry vent stack being so small as to it not being mandatory in the Venting brochure linked above but I cannot find it this minute and I have to leave for a social event. I'll have to research this some more. With that said, I'd like to future proof this installation as much as possible in any way, as long as it would pass 2018 IPC (I assume that if I perform something based on future IPCs, it's not a problem, but being a gov. requirement, I wouldn't be surprised if it's forbidden even if it's a better solution).

5. H would be a 2 inch longs sweep feeding into a 2 inch to 3 inch adapter
A: I believe it's the same as what's listed below, unless I have to write it as a 2" to 3" long turn tee wye, I don't know, the websites don't all seem to use the same terms. I'm still unsure as to whether a cleanout would work on the unused 3" tail section due to proximity to a wall, but if instrument used is a snake, then it should work.
(1) 3" X 2" Long turn tee wye with cleanout and cap/plug
(1) 3" ABS FPT adapter (cleanout)
(1) 3' MPT Plug (cleanout)

I apologize for my inability to draw or insert text in pictures.

THANK YOU, again, and I hope you have a good evening!