2 water closets back to back

**poky1234** · 02-20-2013, 05:45 PM

Hello,

Iam planning a reno in a 2 storey century home. I am located in Ontario Canada and would like to get advice regarding installation of 2 water closets back to back on the 2nd floor , vented by the 3 inch stack vent. I have provided a diagram. Both toilets would be 12 inches away from wall and 3 inch vent runs up through 2nd floor ceiling and out through roof. Both water closets would drop into 3 inch horizontal waste pipe , run 10 feet along joist cavity then turn and drop to basement. I would like to know if this would be to code. I need to run the 10 feet horizontally to reach a wall to drop down through. Any help would be greatly appreciated.

**mtcummins** · 02-20-2013, 08:48 PM

I believe you have it piped correctly, assuming this is all that's on this line (you're not tying into an existing stack - that could change things). I also believe you only need a 2" vent, make sure to tie it in with a combo wye 1/8 bend, not a tee.

But I'm def not up on canadian code, so someone who is, step in and correct me please

**poky1234** · 02-21-2013, 05:06 AM

Thanks for the reply. There will be one lav upstream tied into the 3 inch pipe and a tub , shower and second lav tied in downstream all of which will be dry vented and tied into the 3 inch vent shown in the diagram. I will tie in the dry vents up in the attic. I will use the wye and 1/8 bend to connect the 3 inch vent to the 3 inch horizontal waste pipe. Would this be ok? Thanks

**mtcummins** · 02-21-2013, 06:24 AM

You should probably draw out all of what is being tied in there so that its clear, and then wait for one of the people on here more familiar with canadian code to verify its ok. How things tie together can change things.

**johnjh2o1** · 02-21-2013, 07:13 AM

If your using 1.6 or 1.28 flush toilets it will not work. The new toilets flush so fast that one will pop up into the other. Do a search here on back to back toilets. It has been discussed many times.

John

**poky1234** · 02-21-2013, 08:33 AM

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here is another diagram that might make it clearer. Thanks

**mtcummins** · 02-21-2013, 05:13 PM

I don't want to argue with John, as I'm sure he's far more experienced than me, but I believe your setup to be standard practice. If you didn't have the vent between the 2 WCs, you'd def have problems.

The rest of your drawing looks good to me. You can combine the vents above the flood plain of the highest fixtures, if that makes piping easier... so your tub could go in with the 3" off the toilets, Lav/shower can combine at 42" (typically) above floor into one vent.

Again, this is all based on US though, I know basically nothing about Canadians specific code. And I'd like to hear more input about the toilet thing. I'm pretty sure that the way you have it drawn is how they install commercial bathrooms up to 3 toilets, and would be the same for 4 or more, except they'd bump up to 4" pipe. But not sure, so don't act solely on my word

**johnjh2o1** · 02-21-2013, 05:25 PM

Originally Posted by mtcummins

I don't want to argue with John, as I'm sure he's far more experienced than me, but I believe your setup to be standard practice. If you didn't have the vent between the 2 WCs, you'd def have problems.

The rest of your drawing looks good to me. You can combine the vents above the flood plain of the highest fixtures, if that makes piping easier... so your tub could go in with the 3" off the toilets, Lav/shower can combine at 42" (typically) above floor into one vent.

Again, this is all based on US though, I know basically nothing about Canadians specific code. And I'd like to hear more input about the toilet thing. I'm pretty sure that the way you have it drawn is how they install commercial bathrooms up to 3 toilets, and would be the same for 4 or more, except they'd bump up to 4" pipe. But not sure, so don't act solely on my word

It is by code correct but there will be problems with the new 1.6 & 1.28 gal. flush toilets. (do the search on this forum) Toto among some other manufactures don't recommend piping back to back like that.

John

**mtcummins** · 02-21-2013, 05:36 PM

Originally Posted by johnjh2o1

It is by code correct but there will be problems with the new 1.6 & 1.28 gal. flush toilets. (do the search on this forum) Toto among some other manufactures don't recommend piping back to back like that.

John

Yeah, I have read some of those things over the past couple years.

Do you know if they've changed the way they do public restrooms in practice? How would they pipe a row of 3 toilets, for example, in a commercial bathroom if not that way? Separate 3" lines from each toilet to the stack? How do you tie them all in?

Not trying to argue, trying to learn. Thanks for the input John.

**cacher_chick** · 02-21-2013, 05:57 PM

I thing John is confusing the term "back to back", as the problem which can occur is only when the drains are facing one another such as would be if one used a double sanitary tee on a soil stack. The way the O.P. has drawn them, we cannot see how the connection is being made, with it showing the water closets going into a horizontal branch. If the downstream toilet is connected with a wye, it would be impossible for crossover between them.

**johnjh2o1** · 02-21-2013, 06:03 PM

Originally Posted by cacher_chick

I thing John is confusing the term "back to back", as the problem which can occur is only when the drains are facing one another such as would be if one used a double sanitary tee on a soil stack. The way the O.P. has drawn them, we cannot see how the connection is being made, with it showing the water closets going into a horizontal branch. If the downstream toilet is connected with a wye, it would be impossible for crossover between them.

From his first drawing it looks like one ell with two san. tees.

John

**mtcummins** · 02-21-2013, 06:05 PM

Ok, thanks. That is pretty much exactly what I was thinking. It looks to me that this is not what we typically refer to as a back to back installation, even though they're functioning in the living space that way (tanks are back to back against a common wall).

When I mentioned the wye/45 combo previously, I meant for it to be for both the vent and the 2nd WC, but I don't think I said it very clearly.

Thanks for the input/clarification.

**poky1234** · 02-21-2013, 08:12 PM

Originally Posted by mtcummins

Ok, thanks. That is pretty much exactly what I was thinking. It looks to me that this is not what we typically refer to as a back to back installation, even though they're functioning in the living space that way (tanks are back to back against a common wall).

When I mentioned the wye/45 combo previously, I meant for it to be for both the vent and the 2nd WC, but I don't think I said it very clearly.

Thanks for the input/clarification.

thanks for all your input, to clarify, the water closet upstream is connected to the horizontal waste pipe via a closet elbow , the 3 inch vent stack is connected via a wye/45 and the downstream water closet is connected via a wye /45 combo. Would this be ok? Thanks guys.

**mikeplummer** · 02-22-2013, 03:43 PM

with this lay-out you are wet venting one toilet with the other, which isnt to code, so you would need to have a separate ventfro teh second (downstream) toilet to meet code...or have both toilets connect at the same point of the the 3" via a double san y fitting.

**poky1234** · 02-22-2013, 05:15 PM

Originally Posted by mikeplummer

with this lay-out you are wet venting one toilet with the other, which isnt to code, so you would need to have a separate ventfro teh second (downstream) toilet to meet code...or have both toilets connect at the same point of the the 3" via a double san y fitting.

Thanks Mikeplumber. I will go with your first suggestion, separate vent on the downstream toilet. I didn't want to use a double sanitary y fitting as it would drop everything below the joist cavity. Would I use a 2 inch dry vent and connect it into the 3 inch stack vent above the flood level of the lav?

Thanks again.