Our shower leakes through to the ceiling. Plumbers have bee here, tearing up ceilings, etc, reinstalled tile wall around tub, recaulked and sealed. The last plumber says our pipes are OK, no leaking. He thinks the leak is coming from threshold. Is is possible that water goes through tile walls under the floor? Leaking only occurs when someone actually takes a shower, not while shower is running and draining for the plumber. Thanks. Dee