Our system is working fine. Except. It stopped a week ago when the overflow pan filled. It seemed the condensate pump (6 years old) had died. It was replaced. The new pump did not pump. Bench tests showed both pumps are fine. The line out of the condensate pump was flushed, then replaced. The pump works once or twice then "bubbles up" and doesn't work again. For the last week we've had the condensate pump routed into a bucket which we empty every few hours, depending upon the temperature. The condensate pump need only pump a foot or so vertical, the the line runs 25 feet or so across the attic to the side of the house, then out to the ground. The system works well, but hauling those buckets is a pain. What kind of physics is involved I do not know.