Several 21 year-old double glazed windows have moisture between the glazing. I am aware of a process of drilling small holes at top and bottom of glass and applying a dime-sized micro valve to enable the water vapor to escape, however, there are no venders of this service in my area. The repair procedure seems simple enough to be done by a do-it-yourself homeowner if the micro-valves could be obtained and drilling process explained. Can anyone provide info where to obtain the valves and what type of drill and method to use?