I broke up my basement slab with an electric jack hammer to expose the
drains underneath when I replaced the shower in my basement bath. The
original shower had no base. As far as I can tell, the drain was
installed when they poured the slab since the floor of the shower was
the slab itself. It sloped into a hole into which a standard sink
strainer was placed. I can't imagine it was a retrofit.

Anyway, I was able to expose the cast iron pipes under the floor and
removed the old drain pipes until I reached the Y connector. I then
used a rubber bushing to reduce the 4" cast pipe down to 2" for a PVC
drain.

Since you don't have a drain in the location of the shower, I'm
guessing you're going to have to bust up the floor enough to access the
connection from the sink to the main drain. At that point you may be
able to attach an adaptor to hook up both the shower and sink.


On Dec 6, 5:51 pm, "Joe" wrote:
I have a house that has a half bath on the lower level I want to add a
shower. The only new problem I am faced with is this is a concrete floor, no
crawl space under this one. The sink drain is the closest drain and it goes
straight into the floor. This house is forty years old and is all cast
drains and vent with copper drain lines connecting to the cast ones, no PVC
here. I plan on just busting up the concrete to see what is there. Any one
ever done a job like this? Any input on what I might find would be a help, I
would like to know how deep the sink drain goes down before turning so I can
figure out if the shower will be flush with the floor or will I need to
raise it up?