I am putting in a bathroom with shower, sink, and toilet in my basement. I have already cut out the concrete for my runs and I plan on tying into the main 3" pvc drain pipe that leads out to the city sewer.
1. Can I tie a 2" vent pipe into the main waste stack that is running down from the two floors above that is located right above where the bathroom will be if I use an upside down Y so that no waste coming down can get into the vent pipe coming from below? If this would not be allowed by code then I would have to run the 2" up through the walls to the attic and tye in there?

2. My main question. I need to tie into the 3" main drain under the concrete with a T fitting. I know that with this pipe being buried and being horizontal I am not going to get any play to fit in the T. Can I go pvc to T on one side of the fitting and then use a mission or rubber coupling to join the other side of the T to the 3" drain line? I can't see any other way of tieing in.

Hi Cdwolf:

1) No... if there are fixtures that connect into the stack above the future basement bathroom then you CANNOT install an inverted wye into the stack for venting purposes. Here, you will need to run the 2" vent from the basement bathroom to a FUTURE VENT in the basement, if present (look around for a cap with FV written on it), or you can run it up to the first floor and connect into a 2" or larger vent at a height of 42" or greater off the finish floor, Or, can do the same at the 2nd floor, or you can connect into a 2" or larger vent in the attic. The inverted fitting still applies. Finally, you could also penetrate the roof with the 2" vent by itself if that appears most convenient~~

2) You want to use shielded clamps here. Use two and cut the pipes just short as in the diagram below. You must use a WYE fitting to come off the main drain. No Tee fittings here! Here, you premake the wye fitting with extra pipe length in each end and then measure it. Lay that out on the pipe PLUS 1/2" or so and then make the cuts. Install the shielded clamps, flip the rubbers on themselves and then place the wye/pipe in place. Flip rubbers back into place and slide the clamps in place and tighten... ;)

Let us know what you think...

MARK

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Thanks for all the info.. Exactly what I was looking for. One question on the T vs. wye... Are the long sweeping 90 degrees allowed or absolutely no kind of 90 degree angle fitting? I need the pipe to come off the drain at roughly a 90 degree angle (almost perpendicular to the main drain). If I use a wye like in your diagram is it OK to add other fittings to get it back to the perpendicular angle I need?

You would use a STREET 45 degree fitting to straighten the wye. It will cement right into the wye (why it is called a STREET fitting).

Avoid long sweep 90s unless going from horizontal to horizontal underground. You can use a regular 90 when you stub up for the toilet.

MARK