I have this Kohler shower base that I am about to install. At the bottom of that page it says it pairs well (for them) with their shower drain

Specs here (PDF)

Here are the dimensions for it:

enter image description here

Question: Do I need to find a way to reduce from 2" to 1 1/2" or there is similar parts that can fit my shower pan and that match the 1 1/2" ABS pipe that I have for the drain ?

Update: After reading the below answers and recommendations and after asking around as well I went to the store and I bought the shower drain and both a reducing coupling and a reducing bushing. Both resulted in nearly the same size of the coupling and none of the fits in the space I have below the floor Here are some pictures: -coupling comparison
enter image description here -current situation -everything is 1.5" here but the drain needs 2". The problem is that I need to push the trap downward in order to create room for one of the the couplings
enter image description here Is this an acceptable and functional solution? Does it have any caveats ? The idea is tp put a piece of 1.5" pipe (violet colored in the picture) between the crown of the p trap and the trap itself like below. The yellow pieces will be sized accordingly what you see if just for illustration enter image description here

Update2: OK here are the result of this evening attempt to make room for a lower trap and bigger seal depth

Final result with the drain flush with the floor but there is room to move it higher when the shower base gets in its place enter image description here

Here is the overall height of the assembly enter image description here

And here I am making it easier to measure the seal depth by positioning the tape as needed enter image description here

  • You need to place the reducing bushing (not the bell reducer) directly into the drain outlet (where your picture shows 2" pipe), then you can run 1 1/2" pipe from the trap up to the drain. See my answer. Mar 23, 2021 at 21:07
  • not possible as the reducing bushing is short (3/4") , shorter than the rubber gasket that is 1" tall
    – MiniMe
    Mar 23, 2021 at 21:11
  • Hmm, what is the vertical distance of the violet "trap weir extender"? I believe that the maximum total water height in a trap is 4". You are raising the weir height by altering the trap that way. Mar 24, 2021 at 0:09
  • Please see the Udate2 pictures
    – MiniMe
    Mar 24, 2021 at 1:06
  • looks like you'll be OK, I think the 4" is from the top of the lower trap bend, to the "overflow point", i.e. the bottom of the trap outlet. Looks like you are under 4". Mar 24, 2021 at 1:36

1 Answer 1


You should be able to simply use a 2" x 1 1/2" abs slip bushing in the drain outlet, essentially turning that shower drain into an 1 1/2" outlet:

enter image description here

NOTE- the authority having jurisdiction in your area might require a minimum 2" drain size for showers...

  • I am continuing to use what was there this is a relocation project, not installing brand new. So I am assuming that who worked on this followed the code :-) Is that ABS or rubber ? If the later then isn't that rubber going to age? I guess I could replace it from above, correct ?
    – MiniMe
    Mar 23, 2021 at 13:11
  • I am asking because it is similar to this oatey.com/products/…
    – MiniMe
    Mar 23, 2021 at 13:12
  • ABS.The pipe glues into it on the I.D.; the O.D. is the same as the O.D. of 2" ABS pipe and can be glued into a 2" ABS fitting or would work the same as pipe in drain assemblies that utilize a rubber ring cinch-type connection. Very common fitting that should be available at any plumbing shop or decent hardware store. Should also be available without that "shoulder". Mar 23, 2021 at 17:13
  • Please see my updates, it seems that the suggested solution is not going to work for me. I am asking about an alternate solution, would that work ?
    – MiniMe
    Mar 23, 2021 at 19:18

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