Help on drain vent in shower conversion

[Indyjoh]

Hi. I am in the process on installing shower on 1st floor on concrete slab foundation where a bathtub used to be. I removed the old cast iron tub and tiled walls. This is what's left from the plumbing for the old tub. Since I am installing a walk in shower, I need to removed this and replace with 2" drain line. I'm trying to figure out if the flexible copper line (attached to the ABS waste & overflow) was used as the vent on the tub (or is this just drainage from HVAC in attic above). If so, do I need to replace it by running 1-1/4" vent up through the roof? Or is the vent for this tub drain down the line and shared vent with the toilet next to it? Having a hard time seeing from above in the attic since the furnace/AC is above it and can't see a separate vent. Any recommendation on venting a new shower is appreciated.

Dig a little deeper. P-trap drain goes to the right towards toilet.

 

[MicEd69]

I would guess it is a drain as a proper vent has to be located in the P-trap arm.

 

[pbench]

But there is no vent? Is a p-trap arm vent the same as a vent a few feet down the line? And is it inspector approved for final inspection?

 

[MicEd69]

A P-trap must be vented after the trap and before it enters a horizontal line that has other fixtures draining in it. I used the term "P-trap arm" here to help communicate where the vent needs to be.

If this tub drain was installed correctly, the drain was connected to the toilet sewer line with a wye, and there is a sanitary tee on its back with the tee pointed vertical or no more than 45 degrees off vertical. Assuming the tub drain is a 1 1/2" drain all the way to the sewer connection, that vent must be within 3' 6" or 6', depending on what code the installation is under.

If that line is 1 1/2" all the way to the sewer connection, it will need to be increased to 2" for the shower.

 

[CT18]

That is not a proper vent connection