replacing tub/shower with a shower. Do I need a new vent?

Question

I ripped out a 30 x 60 tub/shower and am replacing with a 34x 60 walk in shower (prefab fiberglass pan). The plumbing is currently a 2" drain that tees into a 1.5" tub drain and 1.5" tub overflow drain. My plan is to cut off the t and replace with a 1.5" elbow connected to the shower drain. Will this work and will there be any venting problems? I.e. is the venting already handled by the existing plumbing (which is below concrete slab I can't see). thanks!!

The tee goes from the main drain to:
1) the shower drain and
2) straight up about 18 inches to the bath overflow drain. So there is not a vent I can see (though I don't know what it would look like). However I'm assuming that it must be vented otherwise I would have already had problems from the existing tub/shower. Does that seem correct?

Answer 1

If the Tee leads up through the ceiling that is the vent. If there is another vent somewhere, you might not have problems

Answer 2

The existing vent would be downstream of where the overflow ties in and should turn up inside a stud wall.
If you did not have any problems with venting before you should not have any now.
Your plan should work fine.
If you can get a 2" Drain for your shower, I would use it instead of the 1-1/2" if possible just to get the larger line size.

Answer 3

2" is code for a reason. The tub overflow WAS the vent! Its called an open (for open air) vent. You need that "t" to connect above the supply line, ideally. DON"T CUT IT OFF! If there is a sink nearby, there is a vent. Connect to it. If in doubt, call, or become friends with, a plumber. (they are notoriously hard to contact... )
Good luck, and be careful!

Answer 4

They can be had for less than 20 bucks, splurge!