On a re-read of your post, I am not sure about the DRAIN PIPE, maybe I am on the wrong fix here, but here is my response anyway! Carol
before the edit:
Yep, search here on MOC using the search engine at the top of the page.
The trouble for MANY of us, not all, but MANY, is that the faucet needs a little tweaking, from the bottom.
If you cannot find the answer from the search engine, contact us at the address on our web page and I will get Al to dictate to me the fix. He is not here at the moment.
Also, we put a cut off plastic milk jug (gallon size) under the faucet, in the access area, attached a little velcro tape to the floor and the jug (as I remember) and used that to check the leaking. Also kept the floor and the storage area dry.
The answer is NOT caulking the shower enclosure, just ask Steve R., our inhouse MOC legend.
Carol