I was called over to a friends house and his shower is leaking. Upon undoing the drain I noted a quarter inch gap between the shower and the drain. It is a concrete floor so this must have always been this way. Nothing looks broken so I am assuming the leak was around the top side gasket. I have but plumbers putty in the gap below and rolled putty to make a new seal for the top gasket and tightened the who thing up.
Now my question is; pvc threaded drain with tape on it should not leak any how so does it matter about the gap as the base and pipe are solid and can not move so nothing can break..
The first thing I would have done is redo the plumbers putty around the drain and concrete top make sure the top has no leak. Once that is solid you can work down from there. I have never used tape on PVC threads as I think you get a better seal without the tape. But if the drain is leaking around the threaded part you may want to check the threads to see if there is a defect in the threads that would call for some silicon tape.
I use the tape just as a lubricant so it is easier to undo in the future. I do not think that the threads are ever water tight. It seems to be holding now so my guess is it was leaking around the top gasket.
I just do not understand why people install shower stalls without the sanded concrete under it to support the base. Just to stop that flexing motion.
If the pipe thread in the floor is the issue it is a big job. Cut the concrete repair the pipe and pour the floor back in.(Not to mention redrywalling the unit back in.)
The plumber at Lowes said it should be ok as ant shower installed in concrete never gets a good seal on the bottom flange because there is no way tighten down on it. We assume often that it is a water tight seal but he said it seldom is.