Main Vent Stack

I am currently working on a one level ranch and have been renovating a full bathroom and a Kitchen. The main vent stack is 3 inches (pvc) and goes through the roof. The bathroom is vented through this 3 inch vent stack . The main stack is not a straigth run, it goes up through the attic and has an elbow then runs 8 feet horizontally and then another elbow up to the pipe that exits through the roof. the entire run for the bathroom vent is 3 inch pvc (sloped back to the bathroom).

I also would like to vent the Kitchen sink / dishwasher through the same 3 inch stack. The Kitchen sink and diswasher use a 2 inch pvc for the vent. My challange is the vent pipe for the kichen comes to the main stack from a different direction (180 degrees.)

My question is how can I tie the kitchen sink into the 3 inch mainstack. Could I remove the elbow and use a 3 inch tee on its back feed the sink vent from one side and the bathrom vent from the other?

Thanks in advance for your suggestions

Yes, tying together branch vents is A-OK. Just don't create any traps in your vent runs where water could collect without being able to drain into some drain somewhere.

Thank you for the response, so there is no issue with the fitting I intend to use to tie the two vent together?

putting a Tee on its back is almost always illegal.

I would suggest that you Tee into the 3" above the elbow, or remove the elbow, make it an upsidedown 3x2x3 tee to pick up the old 3" vent off the bull of the tee, and then a piece of pipe down to an elbow for your 2", or a street elbow if room is tight.

Cutting in above the elbow will be easier, if you have the room. Just hold your 3x2 tee up to the pipe, mark out where the pipes should end (you'll end up cutting out a few inches of the 3" pipe), insert tee. Much easier than cutting out the elbow.

and if there somehow isn't room for that, can you bring the 2" into the attic, around the side, and tie it into the side of the horizontal 3" vent? tying into the vertical portion would be preferable, but if you can't, you can come in this way. just think through your air flow when positioning the tees, so that air flows from the top sweeping down into the vent pipe. It looks upside down compared to the way you put in waste tees.

Thank you for all of the suggestions. I do have plenty of room in the attic so space is not really an issue. I appreciate the great suggestions.

Putting a tee "on its back" would almost ALWAYS create an improper vent, unless the "top" was going out through the roof.

Main Stack Vent

hj said:

Putting a tee "on its back" would almost ALWAYS create an improper vent, unless the "top" was going out through the roof.

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Hj I understand. And to your point yes the top of the tee goes directly out the roof.