Question:My comments on septic tanks are as follows: In a two-compartment tank there is no way to create separate water levels unless flow between the compartments is severely restricted. No one is going to suggest this approach. Different water levels do not create attenuation (slower flow). More attenuation equals more residence time, and residence time equals water volume divided by flow rate. Septic tanks are sludge/ scum separation vessels. More residence time equals better separation. Residence time equals water volume divided by flow rate. For a water volume of 300 gallons and flow rate of 150 gpd the residence time
