Rules & Regulations of the State of Tennessee
Title 0400 - Environment and Conservation
Subtitle 0400-48 - Water Resources (Groundwater Protection)
Chapter 0400-48-01 - Regulations To Govern Subsurface Sewage Disposal Systems (Transferred from 1200-01-06)
Section 0400-48-01-.08 - SEPTIC TANK CAPACITY

(1) For residences, the liquid capacity of the septic tank shall be based on the following:

a For each additional bedroom, add two hundred fifty (250) gallons

(2) For facilities other than residences, the net volume or effective liquid capacity below the flowline of a septic tank for flows up to five hundred (500) gallons per day shall be at least seven hundred fifty (750) gallons. For flows between five hundred (500) and fifteen hundred (1500) gallons per day, the capacity of the tank shall be equal to at least one and one-half (1 1/2) days' liquid sewage flow. With flows greater than fifteen hundred (1500) gallons per day the minimum effective tank liquid capacity shall equal one thousand one hundred twenty-five (1125) gallons plus seventy-five (75) percent of the daily sewage flow; or V=1125+0.75Q where V is the volume of the tank in gallons and Q is the daily sewage flow in gallons. Additional tank volume may be necessary where unusual waste water characteristics are expected from a facility. Expected normal sewage flows may be determined from a list as provided by the Department or actual known water usage data for any facility to be served may be used if available.