500 Gallon Septic Tank / Effluent Chamber – This single compartment tank is generally used as an effluent chamber in tandem with a larger septic chamber, and can be useful when system expansion is the goal. 500 Gallon septic tanks are suitable for 1 bedroom gravity drain fields where allowed by governing permitting agency. Also this tank is used as an effluent chamber for an AdvanTex(c) sewer treatment system. Traffic rated drive-over lids and castings are available as an option along with concrete, PVC or fiberglass risers and lids.