I had a water leak dripping under my shower onto the ceiling below. I replaced the drain (especially the rubber gasket), and now the leak seems to be much less.
It looks like the fiberglass making up the bottom of the shower pan is pourous and water is seeping into it. After shooting the water at the drain or clogging the drain and letting water build up a bit, the fiberglass around the drain appears wet from the bottom.
During my last test, no water actually leaked (dripped) at all, but the fiberglass appeared wet. Is this acceptable?
Pictures of the bottom of the shower pan: