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Thread: 3 inch Wye for toilet below another Wye OK?

  1. #1
    DIY Junior Member Bluegrass Picker's Avatar
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    Default 3 inch Wye for toilet below another Wye OK?

    Hi,

    I have two toilets in separate bathrooms that are back-to-back, and each toilet is approximately 24 inches from the 3 inch vertical stack that goes down below the basement and out to the septic. They are connected via a double sanitary T at the stack just below the bathroom floor, which is in the ceiling of the basement.

    I would like to move one toilet to the opposite end of one of the bathrooms, which would place the drain at a 90 degree angle (or worse) to the sanitary T.

    Would I be OK in capping off the drain at the T leaving the toilet in the other bathroom connected to it's existing connection at the T, and then installing a 3 inch Wye below the sanitary T and then connecting the new toilet drain to the Wye? The distance from the new toilet to the stack would be about 30 inches, and the 3 inch stack is the current vent for both toilets.

    This is the first of probably a few more questions, but thanks in advance for your help.

    Bluegrass Picker

    WA State

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    A double sanitary tee doesn't work well for the new toilets.
    Using a wye below a "santee" for the second toilet may be a good option.
    Double fixture fittings are sometimes used, but I find that on a back to back with modern bowls, that it can force water out of the bowl on an opposing bowl.

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    DIY Junior Member Bluegrass Picker's Avatar
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    Thank you very much for your prompt reply.

    We will be putting the wye in and go that route.

    Our goal is to install a neo-angle shower in the bathroom where the toilet will be moved as in my original post, so the toilet goes to the opposite wall and the shower stall goes basically where the toilet was. We can't put the shower where the toilet is going because of the doorway to the bedroom.

    So, I'll put a 2 inch drain and P trap under the shower (where the toilet was), and I will run the DWV to the 3 inch vertical stack that the toilets currently connect to which is about 24 inches +/- away.

    The current existing configuration: From the top of the stack at the ceiling of the basement (under the bathrooms) I have the 3 inch "santee", then moving downward, the 3 inch copper stack pipe is exposed for 1 1/2 inch, then a 3 inch x 1 1/2 inch Tee (bathtub drain pipe from the other bathroom goes to this Tee), then the rest of the copper 3 inch pipe continues down to a cast iron fitting which goes into the concrete slab.

    If I cut the existing toilet 3" horizontal copper pipe that goes into one of the "santee" inlets, can I put a reducer in the stub to 2 inch and then plumb the shower drain there (after a P trap under the shower)? The other inlet of the santee will remain connected to the toilet in the other bathroom.

    If not, then my next plan would be to cut out the 3x3x1 1/2 Tee below the santee and put a hose clamp coupler on the 1 1/2 stub of the 3 inch pipe below the santee, then put a 3 in x 3 in wye with a 2 in side discharge for the shower drain. This is the wye that we discussed in the original post for the toilet that will be moved. I will connect the 1 1/2 inch bathtub drain line to the 2 inch shower drain pipe that will go into the side discharge of the 3 inch wye. Which of the two scenarios sound best, the 3 inch toilet stub or the wye with side discharge?

    Is 1 1/2" length enough copper 3 inch pipe exposed for a hose clamp coupler to reliably attach?

    The shower P trap would be about 24 +/- inches from the 3 x 3 x 2 wye on the vertical stack, and the stack is the vent to the roof. Would that suffice for a vent for the shower?

    All of these pipes are sweated copper, so I will be using ABS for the new plumbing and leaving the copper where possible.

    Do you have any alternative suggestions?

    Eventually we will be breaking into a section of the basement slab where the 3" vertical stack cast iron fitting goes into the slab so we can install a toilet in the basement. Will any of the above plans potentially affect the basement toilet plan?

    Thanks very much for your help, it is appreciated.

    Bluegrass Picker
    Last edited by Bluegrass Picker; 01-31-2013 at 05:10 PM.

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    Forum Admin, Expert Plumber Terry's Avatar
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    Will any of the above plans potentially affect the basement toilet plan?
    The basement plan needs to be considered on it's own. Before any of it connects to the waste line, it will need to be properly vented to prevent siphoning when the upper plumbing is used. That venting should extend upward, either through the roof, and reventing at 42" above the next floor.

    On the shower above. I don't like the idea of putting it opposite a double santee. I think you are better off bringing up a new line for that with a vent. The trouble with a double santee with new toilets, is that the water skips across. If a shower were on the other end, I can see water being burped out into the shower pan.

    I've been in two homes, one with a double fixture cross and maybe something behind the drywall here. Both homes have skip over.
    Last edited by Terry; 01-31-2013 at 05:20 PM.

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    DIY Junior Member Bluegrass Picker's Avatar
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    Once again, thanks very much for your response.

    Quote Originally Posted by Terry View Post
    The basement plan needs to be considered on it's own. Before any of it connects to the waste line, it will need to be properly vented to prevent siphoning when the upper plumbing is used. That venting should extend upward, either through the roof, and reventing at 42" above the next floor.
    I was kind of concerned about perhaps too many fixtures dumping into the 3" stack.

    Regarding the basement toilet, how about if I run a vent pipe from the basement toilet drain up to the upper floor along side of the main 3 inch stack and then connect to that same 3 inch stack 42" or more above that floor level?

    Quote Originally Posted by Terry View Post
    On the shower above. I don't like the idea of putting it opposite a double santee. I think you are better off bringing up a new line for that with a vent. The trouble with a double santee with new toilets, is that the water skips across. If a shower were on the other end, I can see water being burped out into the shower pan.
    We sure don't want any surprises while using the shower...

    So if I run the 2 inch shower drain to the 3 inch wye with the side discharge I should be OK, but for venting, would the 3 inch stack be the vent or should I run a separate 2 inch vent pipe up to the upper floor along side of the main 3 inch stack and then connect to that 3 inch stack 42" or more above that floor level like described above? There is also a 1 1/2" vent pipe in the same area that the bathroom sinks are connected to. Both the 3" and the 1 1/2" vents go up to the roof. Could I use the 1 1/2" vent as well (it might be easier to connect to)?

    Also, is the 1 1/2 inches of exposed copper pipe that I would have left after cutting out the 3 inch x 1 1/2 inch tee be enough length for a hose clamp coupler?

    We have friends in Bothell and over in that area. Is it OK to suggest that they contact you for onsite plumbing work when they have the need?

    Please forgive the continuous questions, but we thank you very much for your help.

    Bluegrass Picker

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