New construction. Full bath lower on slab, also the drain from a washing machine. Full bath and kitchen sink on floor above.

Two attached pics show the proposed scheme. One shot looks up from under the slab, the other gives a birdseye view.

I should have put labels in the pics, but here goes.

The on-slab bath down has a WC draining into the end ELL of the main, and is vented via the 2" stack a little down the line. That stack rolls up off the san-t in the 3" line, and down from that connection, the lav drains into the line from the vent tee, and the lav is revented up an over as can be seen.

The tub in that on-slab bath has a drain that only can be seen in the from-below view, as I have not shown its trap and stub-up, only the trap arm. That drain is vented as can be seen, with a san-t rolled up at 45 just down the arm a little, then up and over to the 2" stack that is picking up the mainfloor shower.

The upper bath's WC and lav are both drained to the 3" stack shown. The lav's trap arm is 48", and my plumber says that's OK here.

The short stack at the end of one of the drain branches is for the washing machine. That drain is vented with an in-box Redi-Vent by Studor.

The kitchen sink drain is all by itself, and comes into the main the farthest down from anything.

Sorry, but your photo's didn't come through.

Sorry. I added it.

The on-slab bath down has a WC draining into the end ELL of the main, and is vented via the 2" stack a little down the line. That stack rolls up off the san-t in the 3" line, and down from that connection, the lav drains into the line from the vent tee, and the lav is revented up an over as can be seen.

The only issue I see at this point is the Sanitary-Tee's you've installed.

Sanitary-Tee's aren't allowed to be used on their back. This fitting should be a Combo.


The tub in that on-slab bath has a drain that only can be seen in the from-below view, as I have not shown its trap and stub-up, only the trap arm. That drain is vented as can be seen, with a san-t rolled up at 45 just down the arm a little, then up and over to the 2" stack that is picking up the mainfloor shower.


Another Sanitary-Tee on it's back.


The upper bath's WC and lav are both drained to the 3" stack shown. The lav's trap arm is 48", and my plumber says that's OK here.

It's hard to say -- The Uniform Plumbing Code doesn't allow 1-1/2" trap arms longer than 42".

But I'm not sure which of the several codes apply in your neck of the woods.


The short stack at the end of one of the drain branches is for the washing machine. That drain is vented with an in-box Redi-Vent by Studor.


To the best of my knowledge that is a universally accepted use of an AAV.

What is the 1-1/2" waste line dropping into the 3" trunk line picking up?

Thanks for reviewing. Here is a different view, with callouts for the fittings needed to do the under-the-slab stuff.

Every waste-to-waste connection is either a wye, a combo-wye, or a sweep 90. Where vented, the san-tees are rolled at 45 or more.

The 1.5" stack that comes into the sewer main with a combo picks up a shower.

The proposed backwater valve is in the main between fittings 12-13, and 14.

I do not show the vents tying into the 3" stack that pics up the lav and WC above, and which comes into the main through fittings 15 and 16.

A section is given that shows the detail at the lower bath, where the sewer line has the lav drain (fitting 9) and 2" vent (fitting 8) connecting.