Venting question

It is almost impossible to get to the main stack from where I am installing a new bathroom. There is a secondary stack that I can access. Can I vent the toilet to this using a reducer to go from the 3 inch waste pie to a 1 1/2 inch vent pipe? If I can vent it this way, how far up from the toilet do I need to go before I can reduce it and connect to the secondary stack? Thanks.

Are you sure the 1-1/2" pipe that you see is a vent stack? Any fixtures above? If so, it could be a waste stack in which case you can't tie into it with the vent from your toilet. Now that being said, if it is a vent.........

The vent for your toilet can be 1-1/2" right out of the top of the tee. Extend it to at least 6" above the flood level rim of the toilet (where water will overflow from the toilet) before making a change of direction. ie horizontal to vertical. On a personal note, I like to bring the vent on a toilet up to what I would on any other fixture before going vertical...42" above finished floor or higher.

Keep in mind that plumbing codes for your area may be different than what they are here in Ohio. Good luck.

vent

Without seeing the actual layout it is not possible to do anything but be general. Depending on where the toilet is located relative to the rest of the plumbing, you may need a cleanout above the floor so any reduction is size could not take place until after that. Then, most codes will require a 2" vent, and if yours does then you could not connect it to an existing 1 1/2" vent.