I'm adding an addition that will include a Kitchen and a full bathroom with separate tub and shower. I'm a total newbie, so any and all advice is welcome. I'm in California and this will all be below a concrete slab.

Here is an overall image of the addition area with the initial layout with the kitchen sink line on the bottom



The following image is a close up of the tub area. I'm planning on boxing out the area around the p trap so that it isn't under the concrete (at least for the initial pour).

Next is the shower area with the vent in the main 3" line

and finally the toilet area with the tee in for the bathroom sinks (I will add a cleanout at the top)

I’m not trying to be a @#$%& but nothing that was done meets code. Sanitary tees on there backs and on there sides, vents are supposed to be on the branch for the fixture the branch serves, slip joints below slab. Looks like belly’s in the piping. I could go on but I won’t. It may be best to hire a professional

Stick with all ABS or all PVC, do not mix the two as they are radically different plastics and can not be "solvent welded" together ... i.e. they can be glued however the bond will never be as strong as if you stick with the same plastics.

Many plumbing codes will not allow for ABS to be glued to PVC.



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Lots of issues.

Sanitary tees cannot be used to transition horizontal to horizontal, and also not from vertical to horizontal except when it's a dry vent.

Some of your fixtures are not vented. The tub is not vented. You might want to look into wet venting if allowed in your area.

tub is using tubular piping and slip joint fittings below grade. Use SCH40 PVC instead.

the pipe slopes look strange, does look like a belly downstream of the tub. How are these pipes supported? I typically have bricks or pavers (after compacting below) or something solid supporting every fitting in a trench and check the grades accordingly. Then backfill with sand in multiple iterations with repeated wetting once the entire system is done.

what is the reason to mix ABS and PVC? You need a special cement just for those joints. I would go with one or the other but not mixed.

i'm with Plumberpalmer on this.
there are so many thing wrong here.
perhaps it would have been wiser to post a single line sketch of what you wanted rather than go full steam ahead with so many mistakes.
don't get me wrong..
we are here to help.
designing a layout from scratch is so much easier than going back to alter every single fixture connection and vent location.

Thanks for all the input. A lot of this is dry fit and changes can obviously still be made.

In reference to the horizontal to horizontal transitions not being able to be done with a sanitary tee what is the proper connector?

The tub is vented, but perhaps not correctly (the white pvc is for the vent)

The shower is not vented on the branch, but the branch is less than 2' and doesn't go under a wall. I guess venting after it connects isn't allowed. Looking for options here.

I will swap out slip joint p trap.
.
I used ABS for wet and pvc for dry and have cement that works on both.

I will ensure proper support and compacting in trenches.

drain connections used on horizontal must be a "Y".
plastic pipe underground must have fine sand for 6 inches in all directions.
as for the tub connection, cut off the slip fitting and run 2 inch pipe straight into the box you built.
pour the cement and when it is set, knock the box apart, set the tub and use a glue on trap.
after testing, fill the hole with fine sand

your ONLY option is to obtain a building permit

or do you not want the work to be inspected and minimally fit for human occupation ?

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Okay thanks.

It appears the toilet connection is correct and I need to make the other connections similarly with 45 degree wye connectors, correct?

"I used ABS for wet and pvc for dry and have cement that works on both."

That's a bad idea. There are ABS cement that works on ABS and there are PVC cement that works for PVC. The joints are solvent welded. However there is no solvent welding between PVC and ABS, as vic stated above you can buy cement to join ABS and PVC, but it's "gluing" and not solvent welding. The resulting joints will be less strong. Actually most places would recommend using a mechanical joint (like no hub couplings) to connect ABS to PVC.

just took another look at the tub.
the minimum size pipe allowed underground is 2 inch.
so that needs to be changed from the 'Y' used as a vent to 2 inch all the way into the box.
then after the pour, with the tub in place you can glue on a 2 inch trap exactly where you want it and put a reducing bushing into the outlet of the trap so the tub drain can be connected.
the shower vent needs to be moved onto the 2 inch between the trap and the big pipe. that also needs to be 2 inch.
once above ground you can reduce to 1 1/2 for both tub and shower vent.

thanks again for all the input. I have made a sketch of the revised layout and will take into account all the feedback I've received so far.


I will use all ABS, wye connectors for horizontal branch connections, 2" diameter for tub and shower branches, and vents on all branches

Edit: looks like the 1 1/2" branches will need to be 2" as well



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if you make the drain and vent for the double lav 2 inch it will act as a wet vent for the toilet.
just bring the 3 x 2 "Y" closer to the toilet so it is within 6-7 feet and you'll be fine. no separate toilet vent needed.

The fittings that connect the fixture drains to the horizontal 3" can be "combos", like you show in the picture of the shower drain, they don't have to be wyes.

Updated by sketch to correct sizing, use of wye and combo connectors and eliminated toilet vent.

very, very nice..
now, since you have a closet behind the double lav plan on a 2inch cleanout in there behind an access panel.
get a cleanout under the kitchen sink as well.
remember the vents can be reduced to 1 1/2 inch once above ground BUT the toilet/lav vent must remain undiminished in size.

and all the vents can be combined above the ceiling, into a single 2", if you want to minimize roof penetrations.