Sludge and Scum



sludge is the accumulated settled solids deposited
from sewage and containing some water to form a
semi-liquid mass. Sludge settles to the bottom of
the septic tank. The sludge layer should not be within
12 inches of the bottom of the outlet.


scum is a mass of sewage matter which
floats on the surface of sewage in the septic tank.
Scum forms from detergents, grease, or undigested
food (from a garbage disposal).

The scum layer should not be excessively thick.
It should always be less than three inches from the
bottom of the outlet baffle and should not be higher
than the outlet baffle.