I have a fiberglass shower in my master bathroom. I am also on a slab. The other day I noticed water coming out of the ground onto the concrete slab beside my house. I called a plumber and we/he found that the pvc drain pipe had come loose from the drain on the shower. It has dropped down aproximately 1" from the bottom of the drain. After multiple attempts, the plumber and I sucessfully got the pipe back in the drain and tightened back up. Now, two days later, it has come loose again due to me and my wife standing on the floor of the shower. It must move just enough that the o-ring and flange nut won't hold it in place. I am not sure how long it has been leaking, but the dirt below the slab has been washed away allowing the pvc pipe to sag causing it to be very difficult to keep in the shower drain. The only real option I see is to cut the pvc pipe with an inside pipe cutter, add a coupling and a length of pvc pipe, and install a wingtite drain. My question is, has anyone had this happen? How did you repair it? Does the wingtite work pretty well? I really don't want to have to cut my concrete foundation as that would be a major undertaking. I look forward to your replies and thanks in advance for your help.