Question
a round patch of grass dies each year right over our septic tank (which was emptied but not chemically treated last year).  what we do, though, is flush a yeast/hot water/brown sugar mixture down the toilet every month.  is that the culprit? other grass is fine.  our soil has been tested and is ok and we fertilized in the spring. we have reseeded this patch to no avail for 2 years -- the time we've owned the house.  we're in upstate ny and would appreciate any thoughts you might have on this matter.

Answer
Hi Leslie, Two possibilities.  It may be fungal.  Go see your local nurseryman for a broad spectrum soil fungicide that is approved for your area.  You may need to be on the program for a year, especially if you water your lawn frequently.  I'd use a liquid through the growing season (maybe Bayleton if available) and then a fall and early spring granular application with a different fungicide (possibly Eagle).
The mixture you are flushing would not harm your grass.  
The other possibility is a soil problem. If, when the septic tank was installed, the soil they covered it with was a different consistency than your surrounding soil, then the patch may be staying too wet or too dry.  Check the soil 2 days after a rain.  If it appears to be very wet or very dry, then we may have found the problem.
I suspect that is fungal, especially if your seedlings come up and die quickly. You may want to consider a different type of grass.  Many fungal problems are specie specific and may not harm other types of grass. Jim