John, I am going to assume that you have either a algea clogged condensation drain pipe or your primary or secondary condensation pan is clogged or rusted out.
John, do you monthly during AC months run about a cup full of bleach in your pan and into your condensation lines? I do hope so. If you do not, the lines will clogg up with yucky green algea and clog the lines and really create a night mare.
Check your condensation pans and make sure they are not rusted out and than they are not clogged up. The pans all should lean to one side and that creates a fall that drains the pans into the pipe.
Check the pipe, check the pans, check for clogs, THEN JOHN, DO THE BLEACH THING MONTHLY.