Back in the late seventies through the late nineties several septic tank manufactures were building septic tanks with a seam where the upper half and lower half of the tanks were joined. Over time the joint compound sealing the tank halves would deteriorate and leak out effluent. Several older homes are now failing the septic inspection due to this problem. Attached are some close up pictures such a failure. This problem has been corrected by the tank manufactures . They have redesigned the tanks to have the seam above the tank outlet on the top of the tank casting.