Finish stubbed in Basement questions

[DIWHY2025]

Hello, I'm a DIY'er who is embarking on a plumbing journey. Basement is stubbed in for a full bath and that is what I'm attempting to install. I have skills & tools but lack the years of experience this forum can provide. This will be my first attempt to attach to roughed in plumbing. Thank you, in advance for any help.

• Item A in photo. Is a 2 in. x 2 in. x 1-1/2 in. PVC DWV All Hub Sanitary Reducing Tee the proper fitting? Should I go to 2" vanity drain?
• Item B in the photo. Somehow transition from steel to PVC for shower drain? Alternately, remove the steel pipe (has a donut on it at the moment) and use Fernco XHG-2 compression donut or P22U-205 Donut? Trap is in the ground already. Use Hercules® Duck Butter to install new donut into cast hub?
• Short, pitched horizontal run over to shower drain ok?
• Setting prefabricated Kohler shower pan directly on concrete slab. If mortar (mud bed mix) is needed, do I need to prep existing, sealed concrete prior to mud bed? Alternately, is it ok to simply set the pan on felt or tar paper? Is this even necessary?

 

[John Gayewski]

From the vent to the trap is a trap arm. A lav is 1.5" trap arm with a 2" drain in this case because it's likley a wet vent under the concrete.

Follow the instructions with the shower pan each manufacturer has instructions in how to install their pan.

Not sure what your asking about the shower. Use a donut and pvc for the tailpiece of the trap or a no hub band and a caulk less shower drain (jack rabbit from souix cheif).

 

[Sponsor]

 

[DIWHY2025]

From the vent to the trap is a trap arm. A lav is 1.5" trap arm with a 2" drain in this case because it's likley a wet vent under the concrete.

Follow the instructions with the shower pan each manufacturer has instructions in how to install their pan.

Not sure what your asking about the shower. Use a donut and pvc for the tailpiece of the trap or a no hub band and a caulk less shower drain (jack rabbit from souix cheif).

Thanks for your input! As far as my question regarding the shower drain, the vertical stub is currently 2" iron. Would it be better for me to change it to PVC or keep it iron and transition to PVC for the horizontal run to the shower pan? What fitting is best if I need to go from the 2" iron to 2" PVC? Thanks again.

 

[Reach4]

"Vertical stub", meaning the connection between B in your first photo to the new plastic trap? PVC is better. To transition between 2" Cast Iron and 2" PVC in the basement? Fernco 3000-22 or P3000-22 should do that.

If your shower base is cast iron, probably no mortar is needed. If it is plastic, look into mortar blobs.

 

[John Gayewski]

Pvc doesn't rot. It might take 40 years for that cast iron trap to rot out though. It's your choice, but the cast will eventually rot.

 

[DIWHY2025]

"Vertical stub", meaning the connection between B in your first photo to the new plastic trap? PVC is better. To transition between 2" Cast Iron and 2" PVC in the basement? Fernco 3000-22 or P3000-22 should do that.

If your shower base is cast iron, probably no mortar is needed. If it is plastic, look into mortar blobs.

This is what I'm referring to as vertical stub. This is the shower drain and trap, all Iron pipe. I am wondering if I should replace the 2" iron stub with PVC or just leave it. Thought that my skills may be better suited to PVC. Is the iron pipe difficult to remove? Tough to install new donut and PVC into hub?