+---------------------------------------------------------------------------+ | CAPACITIES, DIMENSIONS, AND CONCRETE MATERIALS | | FOR SEPTIC TANKS SERVING INDIVIDUAL DWELLINGS | +---------+--------+--------------------------------+-----------------------+ |_Maximum |_Liquid |_Recommended inside dimensions_ |_Materials for concrete| |number of|capacity+-------+--------+-------+-------+ 1:2-1/2:4 mix_ | |persons |of tank |_Width_|_Length_|_Liquid|_Total +-------+-------+-------+ |served_ | in | | | depth_| depth_|_Cement|_Sand |_Gravel| | |gallons_| | | | | sacks_| cubic | cubic | | | | | | | | | yards_| yards_| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |4 or less| 500 | 3'-0" | 6'-0" | 4'-0" | 5'-0" | 16 | 1-1/2 | 2-1/2| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |6 | 600 | 3'-0" | 7'-0" | 4'-0" | 5'-0" | 17 | 1-3/4 | 2-3/4| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |8 | 750 | 3'-6" | 7'-6" | 4'-0" | 5'-0" | 19 | 2 | 3 | +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |10 | 900 | 3'-6" | 8'-6" | 4'-0" | 5'-0" | 21 | 2-1/4 | 3-1/4| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |12 | 1100 | 4'-0" | 5'-6" | 4'-6" | 5'-6" | 24 | 2-1/4 | 3-1/2| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |14 | 1200 | 4'-0" | 5'-0" | 4'-6" | 5'-6" | 25 | 2-1/2 | 3-3/4| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ |16 | 1500 | 4'-6" | 10'-0" | 4'-6" | 5'-6" | 28 | 2-3/4 | 4-1/4| +---------+--------+-------+--------+-------+-------+-------+-------+-------+ Figure 4.--Single-chamber septic tank. Note alternate use of baffle boards where sanitary tees are omitted at inlet and outlet. The siphon provides intermittent discharge of effluent, which allows time for the disposal area to rest and aerate between discharges. This is more important where the discharge is nearly continuous than in small installations. The frequency and volume of the discharge into the tile field are controlled by the sizes of the siphon and the dosage chamber. The dealer should be informed of the size of the tank and the number of persons in the household, in order that he may furnish the proper unit. A 3- or 4-inch siphon will be adequate for almost any farmhouse installation. Construction