Adding Shower to existing toilet drain

[Keith Kassen]

Hello all, i'm looking to add a shower to our powder room. Is it possible to add a shower drain to the existing toilet drain? My plan would be to move the toilet to the left about 36" and then place the shower in the toilet's original location. Could I cut the line for the toilet and place a long turn tee wye. Or would this create a syphon problem for shower drain. The picture is from below the toilet, also I no longer have access to this area. All work would from above by removing the floor.

 

[Tuttles Revenge]

Yes. You can do it easily by utilizing Horizontal Wet Venting. If your new toilet location will be where drawn, you could add a Combination WYE / 45 (combo) fitting where the 90 up is now. Point it to the toilet. Pick up the toilet with a WYE. Reduce to 2" for the shower and to the Lav. Maintain 2" vent at the sink and take it up through the roof or combine with the original 3" vent.

 

[Sponsor]

 

[Keith Kassen]

Yes. You can do it easily by utilizing Horizontal Wet Venting. If your new toilet location will be where drawn, you could add a Combination WYE / 45 (combo) fitting where the 90 up is now. Point it to the toilet. Pick up the toilet with a WYE. Reduce to 2" for the shower and to the Lav. Maintain 2" vent at the sink and take it up through the roof or combine with the original 3" vent.

View attachment 94960

Thanks for the response. If the Lav already has a drain and vent, do I need tie into it or can I just stop at the toilet? Or does the toilet need a vent in front of it.

 

[Jeff H Young]

normally wying off a w/c "trap arm" is prohibited not sure if that rule went away since venting has changed with the allowing of horizontal wet venting , of cource Keith it wont be a horrizontal wet vent with modification you propose . I cant find exact code at momen but it was always against code could have changed though good question I need to review for my own for just general knowledge as well !

 

[Jeff H Young]

BTW Keith the W/C already has vent (presumably at the wall) but no other fixture was allowed to tie into the trap arm unless there been that change , you could of cource add a santee on top of the santee for the w/c and vent shower that way

 

[John Gayewski]

Thanks for the response. If the Lav already has a drain and vent, do I need tie into it or can I just stop at the toilet? Or does the toilet need a vent in front of it.

What size is the existing vent for the lav?

 

[Keith Kassen]

What size is the existing vent for the lav?

2"

 

[John Gayewski]

Then you're whole bathroom can vent from the lav as shown in tuttles drawing. But everything in the bathroom needs to be tied together.

 

[Keith Kassen]

ok great, thank you for the help.

 

[wwhitney]

The sanitary tee in your photo, does it have the lav drainage coming down from above, and nothing else? I'm going to assume yes for now.

Just to clarify, tie everything together but the lav can't be last. I.e. you can't run the shower trap arm to WC trap arm, and then have both of them hit that san-tee with the lav drain coming down. You'd need to have the lav join the shower first, then join the WC. I.e. put in a san-tee for the shower above the san-tee for the WC (or put in a new san-tee for the WC below the existing san-tee if you reuse the existing san-tee for the shower only).

Cheers, Wayne

 

[Keith Kassen]

There's nothing but the vent above sanitary tee. It goes up about 42" and then all the vents connect to one vent then goes out of the roof.

 

[wwhitney]

There's nothing but the vent above sanitary tee. It goes up about 42" and then all the vents connect to one vent then goes out of the roof.

OK, in that case if you want to tie both the shower and the WC into that stack, you still need two separate san-tees on the stack, an upper one for the shower, and a lower one (could be a wye) for the WC.

Or you could reroute the lav drain (presumably it currently ties into the stack below the san-tee for the current WC), and use it to horizontally wet vent.

Cheers, Wayne

 

[Jeff H Young]

stacking a tee for shower might be too high . horizontal wet venting should work if tuttles drawing is not correct then a 3x3x2 wye could be used and lav wouldnt be last

 

[DeRanger]

Hello, Not sure if I should create a new post or reply here since my situation is similar. Remodelling master bath and moving toilet 3' to the left along the wall and then adding a shower in that spot with a linear drain (with end outlet). Can I do the following:

1.) The existing hole in the joist is too large and I plan to sister it up with 3/4" Plywood so I can notch a 1" deep x 3" length for shower flange.
2.) Come out of the existing drain stack with a 3" 22deg street elbow to a 3"x 2" Long-slope Tee-Wye, to 3" x 3' ABS to the new WC flange.
3.) Off the 3"x2" Long slope Tee-Wye to a 2" long-slope 90deg elbow to a 2" P-trap.

If I recall from my basement remodel where I pulled permits, I can wet vent less than 6'? This extension also puts the WC above the shower drain in the stack. So can all this work?

 

[wwhitney]

For sistering joists, plywood is an inefficient choice, as half of the play run the wrong direction. Use a 2x or two 1x members.

The existing hole in the joist is too large and I plan to sister it up with 3/4" Plywood so I can notch a 1" deep x 3" length for shower flange.

For sistering joists, plywood is an inefficient choice, as half of the play run the wrong direction. Use a 2x or two 1x members.

As to the notch, how deep are the joists?

If I recall from my basement remodel where I pulled permits, I can wet vent less than 6'?

You can not join the WC fixture drain to the shower drain before either one is vented. Horizontal wet venting would involve using the dry-vented lav drain and joining it under the floor first to the shower drain and then to the WC drain (or, since you are in WA state which has amended the UPC, first to the WC and then to the shower). Vertical wet venting via the stack would require that from the top of the stack going downward you have dry vent through the roof, lav drain connection, shower drain connection, and then lowest of all the WC connection.

Cheers, Wayne

 

[DeRanger]

For sistering joists, plywood is an inefficient choice, as half of the play run the wrong direction. Use a 2x or two 1x members.


For sistering joists, plywood is an inefficient choice, as half of the play run the wrong direction. Use a 2x or two 1x members.

As to the notch, how deep are the joists?


You can not join the WC fixture drain to the shower drain before either one is vented. Horizontal wet venting would involve using the dry-vented lav drain and joining it under the floor first to the shower drain and then to the WC drain (or, since you are in WA state which has amended the UPC, first to the WC and then to the shower). Vertical wet venting via the stack would require that from the top of the stack going downward you have dry vent through the roof, lav drain connection, shower drain connection, and then lowest of all the WC connection.

Cheers, Wayne

Thanks for getting back so quickly.

I pulled up the subfloor right over the WC drain and saw that the joists are already doubled up. The outside wall is on the right, doubled 2X10's run 12' to center of house beam. I think I am good on the notch?

As for the drain scenario, the Lav has it's own separate drain and vent.

The WC and shower are the only fixtures I am asking how to tie in. Seen in the middle picture, the current WC has 3" dry vent stack going up inside the wall and that's 16" from the existing drain fixture. You are saying I can't extend the WC 36" (with 22deg, 3x2 long-slope wye, and 45deg) and insert the shower drain off the long slope wye, 6" from the same 3" dry vent stack? I checked a few other places and essentially, I am doing the same thing indicated in this new image which was a recommended method.

 

[wwhitney]

On the notching, you can notch up to 9.25" / 6 = 1.5" but not in the middle 1/3 of the span.

https://up.codes/viewer/california/ca-residential-code-2022/chapter/5/floors#R502.8

In the illustration you attached to the last post, if that 3" stack is a dry vent only, it needs to come off the horizontal WC line via an upright combo or wye, and it needs to rise vertically (at most 45 degrees off plumb). So that little horizontal jog shown at the base of the vent stack would not be allowed.

Assuming you have that, then the way to vent the 2" shower using the stack in is to bring the drain to the stack and connect it just above the combo or wye at the bottom of the stack, with a 3x3x2 san-tee. But the shower trap would need to be within 5' horizontally and 2" of fall from that san-tee.

If your shower trap is farther than that from the vent stack, you can't use the stack to vent the shower.

Note that while your illustration is cropped off, it looks to me like the shower is vented separately, via whatever is attached to that wye in the upper right corner (could be a lav drain for wet venting, or that could be a dry vent takeoff). In which case the WC is wet vented by the the 3x3x2 wye where the shower connects, and nothing relies on that stack for venting.

Cheers, Wayne

 

[DeRanger]

Hey Wayne,
I really do appreciate you responding, but I am not sure I am following on whether I can do what I shared in the original post with the pictures. It is essentially the same as the last illustration which was a recommended solution. But in the first picture I shared is the exact setup I am asking about.

You can not join the WC fixture drain to the shower drain before either one is vented.

I am indicating that I have them vented.

Horizontal wet venting would involve using the dry-vented lav drain and joining it under the floor first to the shower drain and then to the WC drain (or, since you are in WA state which has amended the UPC, first to the WC and then to the shower)

As I mentioned, the Lav is not in this scenario.

As shown in the first picture with the dry fit, can I insert the 3x3x2 long-slope wye, extend the WC drain, and pull off the shower with the indicated p-trap positioned that close to the wet vent?

Respectfully,
Darrel

 

[wwhitney]

I am indicating that I have them vented.

How so?

If you have just one fixture drain going to the stack, and above the stack connection there is no drainage, then the stack counts as the dry vent for that fixture (as long as it's within the distance limit, which for the UPC is 5' and 2" of fall for a 2" shower trap, and 6' from the closet flange for a WC).

If you have two fixture drains going to the stack, and you combine them before either hits the stack, the stack is no longer a vent for either fixture. You would need to provide a dry vent for each fixture independently before (upstream of) they combine with each other. Or you could provide a dry vent for the shower, and let the shower wet vent the WC.

In your picture in post #14, I don't see any dry vent for the shower. So no, that doesn't work.

Cheers, Wayne

 

[DeRanger]

Thank you for explaining, I believe I understand now that adding a 2nd fixture to a wet vent to drain stack situation is what is not allowed without an additional vent.

I happen to have an abandon 2"vent that comes up from the basement on the other side of the window. So can I tie in like this newest image, knowing I am going to have to cut holes in each of the 5 joists to get to it? Does this look legit now?