View Full Version : Drain and Vent question in small bathroom

12-13-2011, 09:43 PM
Thanks for checking this question out. I'm remodeling.
It's a small bathroom in an old house.
Used to have a tub, toilet and sink. I took out the tub and want to make it a shower stall.
From this angle the shower will be on the left, then the toilet in the middle, and finally a sink unseen and revented on the right.
However, I'm not sure my pdraining and venting is correct.
Should the shower drain on the left have a p trap?
Can I tie the shower into the toilet like I have it now? I'm doing this to avoid notching the joist further.
Should I vent the shower or is the wet vent run short enough to use the toilet drain? It's 1.5" pipe and about 3' to the main stack.
The vent stack goes to the roof and is in good shape.
Thank you for any advice you can provide.

12-13-2011, 09:54 PM
Yes the shower should have a P trap right below where you have the capped riser. No you cannot tie it in like you have it, that fitting is not legal there. You will need a vent on the shower in this setup.

I would take out both of those 90s for the toilet, and put a wye basically inset into the chopped up joist, with the wye part going to a toilet elbow, and reduce the 3" top of the wye to 2" for your shower line. You need to use 2 45s or a LONG sweep elbow to make that turn... the medium turns you show on their sides in this picture are not allowed in a drain. This setup would require pulling out the cross brace blocking and replacing it, but would have minimal effect on the actual joists.

You need to vent the shower or the toilet flushing will siphon the trap.

There seems to be some other problems in your picture as well, but thats a start... pretty much all that you have there needs to be redone.

12-13-2011, 10:07 PM
Actually, looking at the pic again... you might as well cut into where I assume the tub dropped in before and bring your drain for your shower over there. That will make venting a lot easier to get up into that wall.

Also, it looks like the 3" wye where the stack comes down and the toilet breaks off is pitched backwards. That will become a big problem over time. I kind of hinted at it before, but didn't directly mention it... the 90 off the top of that wye headed toward the toilet cannot be a medium 90, it needs to be a long sweep.

Is the opening on the top left the door, or is that a wall? If its a wall, you probably need to tear out everything up underneath that wall and redo it from there over to make this work. Assuming that will be a wall, I'd move the entire wye assembly to the left more, then use a 45 off the end of it to go straight to the toilet location if possible, or use 2 45s to kind of jog it over if necessary. That will require redoing the 3" going up to the stack on a 45, and moving a wall stud.

Your sink can come across inside the wall and tie into the 3" vertical stack with a 3x1.5 or 3x2 SanTee. You will need to pull a vent off that and take it up above the other fixtures and tie it back in to get a proper vent.

12-13-2011, 10:35 PM
Thanks for this, mt.

1.The cap on the left near the level is where the tub used to drain. I was thinking of pitching my shower pan drain in that direction, put my p trap there and revent up to the stack like it was before. This also avoids nothcing my joist.
2. I moved the wires and reupped a pic. I'll check the angle of the wye back to the toilet but you say it must also be a longer sweep?
3. That is a wall and I'm restudding which is why I decided to make sure this was closer to correct before framing. If I move the wye to the left to allow for the longer sweep your saying I'd have to tie in a 45 to the main stack, correct?


12-13-2011, 11:02 PM
That should work for the shower pan, just make sure you get proper pitch on the pan to the drain.

The wye itself is ok there, but it seems to pitch downwards. That 90 is a medium 90, you can't use that on its side. It can only be used in a drain to go from horizontal to vertical. You would need long sweep 90s to do it the way you have it, but that would require moving the wye down to do it w/o chopping out more wood etc. The other 90 with the inlet is not allowed to be used like that at all... that fitting is for a toilet entering the opposite end of the elbow, then dropping vertical out of the end you have attached to the closet elbow, with a 2" vent coming out the top. You can't dump into it like that.

The long sweep 90 and the 45 were two different ways of doing the toilet. you could pipe the toilet (w/o the shower tie in) the way you have it, if you put in 2 long sweep 90s instead of those mediums. However, this will still require moving the wye over, and if you're doing that much work, a much better way would be with one 45, as i drew on your pic.

Sorry its messy, I'm on a laptop and drawing on there is tough to be neat. Hopefully this shows what I was saying... the yellow is showing to move the wye over and do the necessary changes to the stack to make that work. The blue are notes about the proper fittings, etc. The red are how lines would run. This isn't quite complete, but I noted a number of the things you'll need.

I'm not sure, but you may also need a 2" vent for the toilet in this setup.


12-13-2011, 11:21 PM
Thanks for taking the time, mt. I really appreciate it.
I'll mock up what I got out of your instructions tomorrow and repost to make sure I have it right.
Again, thank you for taking the time to draw in ideas.

12-14-2011, 06:35 AM
Sorry to sound cold, but this is one of the worst examples of work I have seen in a long time. Is that floor joist cut and capped with that metal contraption?

Why is the blocking notched?

No holes should be drilled through that floor joist than come within 2" of the top or bottom of the joist. That floor joist should have first been sister and then drilled - if OK'd by a structural engineer.

I recommend you cut it all out. Repair the framing and try again.

12-14-2011, 08:25 AM
From the looks of it, I think there may be a partition UNDER that joist which would make your "recommendations" moot. You MUST have long sweep 90s to make your turns. You CANNOT use a "heel inlet" for the shower and especially NOT when you are using it to "reverse" the flow. THe shower needs a "P" trap AND a vent. The capped pipe in the wall will have absolutely NO function if is is used for a vent.

12-14-2011, 09:26 AM
A 3" hole was drilled through the joist by the previous owner so were were trying to strengthen by steel plating it. Point taken, though, now that it seems the 90 won't work into the main drain I may have to sister it anyway.

12-14-2011, 03:54 PM
hj, if you took my "vent" label at the top left to mean that stub out, it wasn't. The stub out should be cut out when moving the wye over. That was labeling the sketched red line coming up off the shower drain as a vent line, to be tied back to the stack. Does the rest of my sketchy drawing look ok? I'm not a master plumber, just trying to help a guy out. Also, does the toilet need a separate vent in this setup? I'm not sure due to the horizontal main drain there... is the vertical part of the stack sufficient to wet vent the toilet?

While you have this chopped out, you should sister the joist and drill only the necessary hole through the new wood. Even if there is a wall under it, it wouldn't be a bad idea, as interior partition walls aren't built to carry load (at least usually not when they're parallel to the floor joists).

12-22-2011, 05:22 AM
It is a "distributed load" so the interior partition under the joist will be MORE than adequate to support it.