SEPTIC TANKS, CESSPOOLS, AND
Septic tanks are constructed of reinforced concrete.
The length of the tank should be not less than two
nor more than three times the width. The liquid
depth should not be less than 4 feet for the smaller
tanks and 6 feet for the larger ones. Manholes
should be provided over the inlet and outlet pipes
and over the low points in the
Septic tanks, cesspools, and leaching fields are
used for sewage treatment processes where
common sewers are not available. These facilities
are for the most part underground receptacles. If
properly designed, constructed, located, and
operated, these receptacles work without
objectionable odors over long periods of time with
a minimum amount of attention.
Septic tanks may be used to serve small or
scattered installations where the effluent can be
disposed of by dilution, leaching wells or trenches,
subsurface tile, or artificial subsurface filter systems
The septic tank capacity should equal a full days
flow plus an additional allowance of from 15 to 25
percent for sludge capacity. The minimum
acceptable size of septic tank is 1,000 gallons.
Table 10-14 outlines the minimum tank capacities
required by the National Standard Plumbing Code.
Figure 10-2.Septic tank
Table 10-14.-Capacity of Septic Tanks