How to connect my reno drains?

My 'big picture' involves making the ensuite bath a tad larger by stealing room from the adjacent main bath. In the process we will also enlarge a bedroom closet.

The first project will be taking care of the main bath, while maintaining use of the existing ensuite shower, etc.

The old monster jacuzzi tub has been torn out and a new soaker tub is to be installed about 5' further away against an exterior wall. The toilet is moving 18" further into the room (along its same joist) to make way for the tub. What I want to know is the best way of tapping into the existing plumbing stack (where current shower is and the previous jacuzzi used to be plumbed into) -- see .jpg of existing crawlspace plumbing.

To maintain the existing shower (but to prepare for its move in the next project phase), what I propose to do is to cut everything back from just below the current shower wye and down to the 2" lateral going to the main sewer line. Then connect the new tub drain (Canadian Code seems to ok up to 8' trap arm for a 2" drain) to the remaining lateral using a new wye, and another new wye with a stub out (capped) for the future shower drain (about 4' away from the vent stack). As you may see these new connections will now be down about 2.5 feet from the original connections up near the floor joists. I would then finish off the 2" lateral with a new cleanout at the end.

Later, in the next phase I plan to go back and cut off the old shower drain trap at its old wye and just cap it.

So in essence, the whole stack from the new lateral wye's on up would just be an extension of the existing vent.

Do you think this is a workable plan, or perhaps suggest better alternatives?

I can't read through your description and see it in my head.

If you have one fixture connected over the other one (as it is now), the lower fixture is required to have a separate vent or be re-vented.

Instead of re-posting as you have, it would be easier to decipher if you were to draw us an isometric diagram of the DWV as you are proposing to install it.

This is also what any plumbing inspector will want to see prior to commencing work.

Thanks for your reply.

I tried to explain my plan as easily as possible. But here is a drawing of what I want to do. You may be able to compare that to the photo.

I figure that keeping the stack the way it is, but of course cutting off all the trap arms and capping them, this will essentially provide just a lateral with a vent. Then, using a couple wye's I could then connect the new trap arms into the lateral (just after the bottom 45 and before it goes vertical).

But, in the meantime I still wish to keep the original shower drain, so again my thoughts were to cut just below its wye (I guess I should say,'tee') and cut again just past the lowest 45, then add a clear piece of ABS (that makes it neater) up to the old shower tee). -- this make more sense?

I don't know where people get the idea they can attach a piece of pipe just any old place
and call it a "vent". Your diagram shows NO vents. Vents must take off vertically (or almost)
from a trap arm. A trap arm cannot connect to any other drain pipe before it is vented. The
vent connection must take place within a prescribed distance from the trap (varies by code,
my code specifies 60" for a 2 inch trap arm, assuming a standard 1/4 in per ft pitch on the
trap arm).

I'm not a plumber and drew the schematic as best as I could aim for, given the existing structure. Have you looked at the photo of my current configuration? Have you read my discription? The existing vent is at the top of the stack as it goes into the subfloor. In Canada (and my local code) says I can go 8' with 2" trap arm to a vent, assuming a standard 1/4 in per ft pitch on the trap arm.

So I'm asking, can you suggest a better way of this DIYer accomplishing the goal?

duplicate post

Every trap must have it's own vent.

The vent must rise vertically from the horizontal trap arm within the maximum distance allowed by code. No part of the vent can run horizontally until it is at least 6" above the flood rim of the highest fixture served. At that point they can run horizontal (with pitch) to a vent stack.

The way your stack is currently set would meet code for a vertical stack IF the tub drain were re-vented. Because the shower waste flows past the tub waste, the tub would be required to have a vent in the trap arm.


From what I have seen here in the forums, Canadian plumbing code is not exactly the same as the USA, but it is quite similar.

cacher_chick said:

Every trap must have it's own vent.

The vent must rise vertically from the horizontal trap arm within the maximum distance allowed by code. No part of the vent can run horizontally until it is at least 6" above the flood rim of the highest fixture served. At that point they can run horizontal (with pitch) to a vent stack.

The way your stack is currently set would meet code for a vertical stack IF the tub drain were re-vented. Because the shower waste flows past the tub waste, the tub would be required to have a vent in the trap arm.


From what I have seen here in the forums, Canadian plumbing code is not exactly the same as the USA, but it is quite similar.

Click to expand...

So, it seems the current old tub trap arm (the one that's disconnected in the photo and temp plugged with a plastic rag) config in the photo is incorrect, even with that stack vented?

With my mod, can I satisfy the problem by doing this? -- cutting most everything off from the floor down to the lateral, then replace with a straight hunk of ABS, then cut in a tee for the tub arm now (that would then provide that existing vent for it). Then later go back and cut in another tee for he shower arm below the tub tee and revent that arm back up to the top of the stack -- sort of like this..



BTW, the house is one-story rancher.

You have the right idea, but the re-vent must come up above the floor. Normally there would also be a lavatory on the stack so the re-vent would be above the floor at least 42".

"Vent shall rise to 6” ABOVE flood-level rim of the highest fixture served before being connected to any other vent."

The flood level rim is the point which water would run out over the top of the fixture.

This include a re-vent.

cacher_chick said:

You have the right idea, but the re-vent must come up above the floor. Normally there would also be a lavatory on the stack so the re-vent would be above the floor at least 42".

"Vent shall rise to 6†ABOVE flood-level rim of the highest fixture served before being connected to any other vent."

The flood level rim is the point which water would run out over the top of the fixture.

This include a re-vent.

Click to expand...

Yuk! Re-venting above the floor could be a big wreck of the wall above, especially when it houses the old current in-use shower stall. And no, there is only a shower against that wall, no lav.

So, looking back at the photo, in your opinion was the original tub trap arm installed wrong? ..it had no separate vent and was simply installed on the stack below the current shower trap, which you seemed to indicate as a no no. I can't attest to its overall draining ability as we hardly ever used that Jacuzzi tub ..but looking back it seemed a tad slower than normal to drain -- I chalked that up to the 1 1/2" trap and arm size Meh... aside from the remnants of the trap arm, the tub is gone now anyway.

This is a helpful discussion, so thanks

Any fixture connected below the top-most drain on a stack is required to have it's own vent, either individual or re-vented back to the vent stack, at least 6" above the flood rim of the highest fixture served by the stack. Your tub connection would not have passed inspection here.

A lot of houses were plumbed in decades past that are unacceptable by today's standards. Existing construction might be grandfathered, but any changes or additions will be required to meet the current codes.