Most condensate leaks are caused by clogged drain lines.  Other factors
could be improper installation of equipment or cracked or rusting drain
pans.  Cleaning the drain lines should cost no more than $40
Phone: (757) 506-6488
You should have your drain lines cleared out once
a year.  This is usually done during maintenance.  
code to put a p-trap on the drain lines and mold and
gunk get caught in the trap and water backs up into
the coil drain pan.

A secondary drain is attached to a higher point in
that will dump the water into an emergency drain
pan placed below the unit.

This will keep the water from spilling into the ceiling
as long as that pan is draining properly.

It is a good idea to have a float switch or "ceiling
protection kit" installed in the emergency drain pan
to shut down the unit if the water is not draining
properly
shut down power if there is a problem.

The pan is not expensive but getting the coil out of the unit can be difficult at times.  This repair should not cost more
than $200.

If your emergency drain pan is rusted out or not level and has to be replaced you can often times raise the unit and
slide the old one out and new one in, with help of course.  This should be no more than $180.

If the unit has to be removed and reinstalled it could be as much as $400 or more, depending on what needs to be
done.  Companies often charge over $800 which is way to much, you need to call around and explain what needs to
be done and get a better price.