Toilet plumbing question

[Tommy Dee]

Hi,
Adding a bathroom toilet to existing main stack, can I connect using a double 90 or double wye. I can either do it on its side horizontally or vertically where it penetrates the floor. See attached photo. 3in main stack comes up through the floor then turns 90 to avoid a joist then 90 again towards the left then 90 up again through the roof. Toilet will be added to the left and the stack continues to the right and then goes up through the roof.
Thanks!

 

[wwhitney]

If the stack in your photo is serving as the vent for fixtures on the floor level below (likely), then you can't use it for drainage from fixtures on this floor level. You'd need a separate drain stack alongside the vent stack, which can connect to the existing stack at an elevation below the portion of the stack that is used for venting (dry or wet).

Cheers, Wayne

 

[Sponsor]

 

[Tommy Dee]

If the stack in your photo is serving as the vent for fixtures on the floor level below (likely), then you can't use it for drainage from fixtures on this floor level. You'd need a separate drain stack alongside the vent stack, which can connect to the existing stack at an elevation below the portion of the stack that is used for venting (dry or wet).

Cheers, Wayne

Ya, I will be bringing up the vent from the lower floor level and connecting it higher on the upper floor above the fixtures. That’s easier for me than running a new drain stack and connecting it lower down.
What would you recommend in terms on connecting to that drain stack? Thanks

 

[wwhitney]

OK, so functionally, once you've rerouted the vent(s) from the floor below to connect to the upper portion of the stack on this floor, you could delete the stack between the highest drainage connection on the floor below and the vent reconnection on this floor. Of course, you want to repurpose some of that for drainage for this new WC, rather than delete it, but the rest can be deleted.

In other words, you can cut out the elbows shown in your photo and replace the ninety degree elbow under the joist with a new one whose inlet is pointed in what ever direction is convenient for your drainage on this floor. Then the question is just how are you planning to vent the WC? There is not alot of distance between the closet flange and where your drain goes down through the floor.

If your bathroom is going to have other fixtures draining into this existing stack, then that presumably includes a lavatory. If you dry vent the lavatory, it can horizontally wet vent the other fixture(s). So you'd just need to connect the drain carrying the dry vented lavatory (and possibly wet vented tub or shower) to the WC fixture drain between the closet flange and the existing stack location. E.g. with a 3x3x2 horizontal wye.

It looks like there would be room to fit all of that in there. If there's not room horizontally between the closet bend and the stack, you have other options. E.g. closet flange, 45 degree bend, 3x3x2 wye, 45 degree bend to turn down to the stack, if that happens to line up. Or if you have enough height, you could do closet flange, closet bend, quarter bend to turn down over the stack, 3x3x2 san-tee or wye to receive the lavatory (and possibly tub/shower) drain.

Cheers, Wayne

 

[Tommy Dee]

Ya, there will be a lav and that would be draining into the right part of the stack that’s in the picture so I wouldn’t be eliminating it. I guess my question was how to add the WC to the left side and keep the right side. Was therefore asking if a double wye or double 90 would be ok. Or on its side right after the 90 bend come up from the floor if there is no room under that joist in the picture. If those would be good options.
Thanks again for your time

 

[wwhitney]

Ah, you could use a double wye or double combo with the barrel vertical and just cap the top entry. You could also tilt the barrel 45 degrees off true vertical if you like.

Another possibility is to use a 3x3x3x2 san-tee with sanitary side inlet, again with vertical barrel and capping the top entry. That would give you two entries 90 degrees apart in plan, which may or may not work for your layout.

There is also a fitting called a double quarter bend, which you could use with the outlet vertical or at a 45 from true vertical if both inlets are horizontal. Not commonly used but this application is probably appropriate for it. May be hard to find.

You don't want to use a double wye or double combo with the barrel horizontal, as they are planar fittings, while the the proper geometry for that would not be planar. The side entries would both be slanted upwards out of the plane made by the barrel and a perpendicular horizontal line.

So if you ever need to bring two drainage lines into a horizontal line, use two wyes in a row (the upstream one could be street to be most compact). That would let you independently adjust the slope of each inlet.

Cheers, Wayne