Septic Systems
At a site I checked it was stated that a garbage disposal
in a septic system should be considered and as affecting the system as if it were an additional bedroom. Typically the requirements of a septic system are driven by the number of bedrooms (in residential use applications) as this indicates
the number of humans in the household. In the good old days,
most kitchen drains along with laundry used a gray water
system. Gray water systems typically don't include substantial solids. The bad thing about having a garbage disposal on a septic system, is that it promotes the introduction of fats/oils into the system. The bacteria that
promote the break down of the solids to sludge do not work well with fat/oil as part of the process; hence the use of a gray water system. Also of course, heavy concentrations of bleach and detergents kill the waste gobbling bacteria. So,
plumb the kitchen sink w/wo gd and the laundry to a gray water system and the septic system will last indefintiely,
with a pumping every five to ten years. While you're at it,
put a grease trap on the gray water system so butter and meat fats don't clog the small leach field that these systems require!!!