ABS Branch Connection Question

[adam1703]

Hello,

I plan to move my plumbing around my house to open up the ceiling height and do a bulkhead around the room's perimeter. I'm wondering if I can connect the shower, toilet and vanity drain lines as a branch the plumbing stack or if each fixture needs its own line to the plumbing stack?

I planned to replace the cast iron with PVC while the area was all open and do a continuous stream of ABS pipe around the wall so I could get my ceiling back. Would this follow code, or anything else I need to bare in mind if I'm doing this? If it's not allowed, can you please let me know why?

I've included a rough diagram of what I'm thinking;
The drain from the tub/shower goes into a 1-1/2 ABS pipe. My thinking would be to connect it to a branch that connects to a 3" ABS Pipe (when it reaches the toilet) and eventually connects to the vanity with a 1-1/2 line. Then connecting to the current 4" Cast Iron Plumbing Stack (which I plan to replace with a 4" ABS plumbing stack.

I also had one more question, what's the minimum size for a plumbing stack vent? I believe it's a 3" cast iron vent that's currently installed.

Thanks for your help!
Adam

 

[MicEd69]

It looks like your existing plumbing has some venting issues. It appears that none of the fixtures you want to combine are vented. The vanity might be, but I rather doubt it.

But what you want to do is mostly possible. You will need to be sure to get 1 in 50 slope on all the drain lines, and you will need to provide proper venting for the tub/shower which will also provide a wet vent for the toilet. However, the vanity cannot be connected between the toilet and the stack, so that will need to be run as a separate line to the stack and it will also require a separate vent.

 

[adam1703]

@MicEd69 At the moment, I'm not looking to demo the bathroom upstairs for vents, so I'm thinking if I replumbing it the same way it is currently along the wall, it shouldn't cause any problems, right?

Then down the road, once I'm ready to reno the bathroom upstairs, I can add the vent lines for the vanity and tub/shower

 

[MicEd69]

"...if I replumbing it the same way it is currently along the wall, it shouldn't cause any problems, right?"

Maybe but maybe not. If you tie the tub/shower into the new 3" line as the toilet without a vent, every time you flush the toilet, you could pull the water out of the tub/shower trap.

If you run all three lines separately around the edge of the room, the tub/shower drain will be longer than it is now, and it will have to turn 90 degrees. The tub/shower line is pretty long to the stack now, so making it longer could cause problems.

And if I'm reading the Ontario Code correctly, no fixtures can be tied into a line between a toilet and the stack.

So, your piping is not per code now, your future plans are also not per code unless you vent the tub/shower which will also vent the toilet, and you could make matters worse.