Are you sure it was a half inch of fall or was it a half a percent grade, ie a 0.5% grade  .5 is not too bad.   1/2" is the depth of your footprint in the dirt.  
(0.5)=  6 inches in 100'  that would be a huge difference.

If the main is put in deep enough to let you start out say 4 or 5 ft deep at the start and end with 2' of cover you would have some grade there also.  Hard to tell without some numbers like main depth, inches of cover at main, length of run, elevation numbers along line, etc.  Hope it works out for you.  Nothing worse than not having a good outlet.