Hey everyone. I got a drain kit for my leg tub and I made an error. Here's the and exploded parts diagram I'll be referring to:

http://www.kingstonbrass.com/v/image...ion/CC2098.pdf

When I removed the old brass plumbing and tiled the floors, I left part 8 connected to the 1/2" PVC piping under the house with a compression slip nut, thinking I'd reuse the old plumbing. We decided to get some new brass plumbing, however. I'm sure most of you know that the new stuff I got was 1-1/2" OD brass tubing. It turns out the old plumbing was 1-3/8" OD brass tubing, so part 8 from the old kit doesn't fit up to part 7 (the tee) from the new kit. The ID of part 7 has 1-1/2" fine threads and the OD has 1-1/2 compression nut threads. The OD of the old part 8 has 1-3/8" fine threads and the OD of the new part 8 has 1-1/2" fine threads. So, it looks like I have a few options:

1. Find an 1-1/2" to 1-3/8" reducing washer to put in the compression nut between the old part 8 and new part 7. Would this seal appropriately, without also using the fine threads between parts 7 and 8? Are those threads really needed? I found this (LASCO 02-2269 Rubber Reducing Slip Joint Washer, 1 1/2 x 1 3/8-Inch - - Amazon.com). A special compression nut is also recommended with it. Is that necessary?
2. Attempt to chip away at tile and subfloor to fit the new, 1-1/2" tubing through and connect it to the drain
3. Take the more ingenious route and cut the new part 8 to fit flush against the floor, slip it over the old part 8, the annulus filled with silicone sealant. Connect the new part 8 to the new part 7.

What do you folks think? There's also the option of getting a 1-1/2" fine thread to 1-3/8" fine thread bushing to attach the old 8 to the new 7, but I haven't had any luck coming across that and it would either put the compression washer over the OD threads of the bushing or over the 1-3/8" OD of the old part 8.

 

Sorry, I've been using "compression" a lot when I mean slip joint.

I also found and 1-3/8" slip joint nut with "d-ring" at this site:

https://www.plumbingsupply.com/tubul...s.html#washers

Theres also a 1-1/2" slip joint to 1-1/4" reducing tube here - which would fit through the hole in the floor for the 1-3/8" tube. On page 34

http://media.wattswater.com/PL-WBT.pdf

 

No silicone to seal any drain parts, this is just not done.
I recommend you install the new 1-1/2" drain kit down through the floor and continue with 1-1/2" all the way to the tee under house.