How do I convert a bath tub drain to a shower drain? The bathtub drain is an inch and a half pipe and I need to convert it into a 2 inch PVC. The house that I am working in has a concrete foundation.

Look at the San T to which this 1 1/2" tub drain connects. In most cases, it is 2"x 1 1/2" x 1 1/2" San T. If that's the case, you would just replace the San T with 2"x 2" T.