Hello all, new to the forum and looking for some answers. We live in a new construction home and are in the process of finishing our basement. The bathroom is giving me some trouble. Please see the image below. There is a wall in the foreground so try to ignore that, just wanted to get all pipes into one picture. The tub will go all the way to the right. The vanity/sink will be where the blue box is in the picture.

I assume the 3 pipes I put a red box around are vent pipes. The two on the ground are both 2", assume one is for the tub vent and the other is the toilet vent. The one in the ceiling is 1.5", maybe because it is a dry vent only? Trying to confirm if what I am assuming is correct and if all should be joined together.

To the left of the picture are the waterlines in the yellow square. I will bring them down to the sink (blue square) for the inlet for the sink water lines. Then tee hot line (orange) to the tub. The cold line (blue) will tee from there off to the toilet and continue onto the tub.

Last and most troublesome for me to understand is the sink p-trap. Should this be run to the toilet waste/vent like I have it drawn in the picture? All white lines are vent lines and/or waste/vent from sink p/trap.

Should I be utilizing the 4" pipe all the way to the left in the picture next to the sink?

Attachment 48073

Thanks for any and all help!

Green is the toilet drain, Red on the right is the tub drain. You use the term "vent". I believe you mean drain for some of the items. Pipe in the red box behind the toilet is probably the vent. The pipe from the ceiling, if indeed a vent, should be 2". The maximum distance to a vent from a 2"drain line is 5 ft. On the sink "P" trap, I would use an Air Admittance Valve (AAV) at the sink and avoid length of drain issues. It is hard to tell floor layout from the pictures but it appears the tub will be in an alcove?

The first thing to check here will be to cut off the cap at the pipe coming out of the ground at the tub area... simply cut the cap off and then pour water into the pipe. After you do that, use a flashlight and shine it into the pipe and see if you observe any water remaining in the pipe. If you observe water then this is the tub PTRAP and it is not a vent. If you do not observe any standing water then it is indeed the tub vent and will connect into the toilet vent at a minimum of 42" off the floor. Further, if this is the tub vent, you'll need to remove the foam insulation in the hole and find the PTRAP so you can hook it up to the tub waste and overflow assembly.

The sink PTRAP drain pipe will connect into the toilet vent at about 17" to the center of the drain off the floor (end up about 18" off the finished floor at PTRAP). There should NOT be a need for an air admittance valve in this case.

The 1.5" vent in the ceiling should be a FUTURE VENT. The future vent is 2" in many states, but can be 1.5" as well (check local code). The bathroom group vent will connect into the future vent.

I like to see a 2" clean out tee fitting at the toilet vent pipe just before it goes into the floor...stub the cleanout out of the wall for easy future drain access). This is required by most state plumbing codes that I know of...that, or its also just a good idea!!

You should not be utilizing the 4" pipe on the left, but you do want to keep the cleanout accessible for the future... they sell quick install access panels for this purpose (available at all home improvement stores).

Final note, the toilet drain is 4"..I would install a 4" inside toilet flange that simply inserts into the toilet drain pipe (usually cut flush to the finish floor). Mount the toilet flange AFTER the tile is set and secure the flange through the tile and into the cement floor for the best toilet install.

Determine if that pipe is the tub PTRAP or vent... post back with questions.

Mark

Thank you both very much, appreciate the time taken to respond to my questions.

Mark, I'll definitely cut the cap off and let you know what I find out about the pipe by the tub.

Thanks,
Ash

Ash,
Excellent advice is being offered as usual, and I have a tip to share as well - a standard 3" pvc hub closet flange fits snugly into 4" pvc pipe.
The state of Connecticut recognizes ( as do all New England states except MA ) and has adopted the 2012 IPC & the 2009 IRC regarding plumbing & venting; each authority allows a 5' waste arm/ vent for a 1.25" trap, a 6' waste arm for a 1.5" trap & drain, and an 8' waste arm for a 2'' trap...