"Jeff & Kathy Brown" wrote in message
. ..
What would cause the water in the toilet tank to drain out completely?
There isn't any outside leak. Would it be the gasket at the bottom of the
ballcock? I put in a new ballcock thinking that this was the problem but
the water is still draining out. Any suggestions would be appreciated.

Best let a plumber "pipe up" on this group, but when that happened to me, I
found that my roof vent pipe had been plugged with leaf litter, so that when
another part of the house or street sewer piping created a partial vacuum
due to normal water outflow, the bowl was sucked dry. The ballcock is not
the problem in your case, as far as I know. Check for clogs in vent pipe.