1. No, except if you can shut off the water at the shower head, that can aggravate a slow leak that pre-existed in that section of pipe. Where exactly (within three inches) did the plumber say the leak was?
2. Yes, if the material collects just after the two toilet drain pipes join, below first floor level.
2. Yes, if the material collects just after the two toilet drain pipes join, below first floor level.