these aforementioned conditions was found to occur when the spacing between upper end 30 of influent pipe 20 and inverted cone 28 was 5 inches a wide range of dome deflector and inverted cone dimensions have been shown to provide adequate mixing for a variety of sizes of ept tank and influent flows for example the width of the base 36 of inverted cone 28 preferably at least as wide as the width of the impinging flow which to a good approximation is equal to the inside diameter of upward directed influent pipe 20 inverted cone 28 preferably has an aspect ratio height width of at least 0 2 to redirect effectively the vertical flow from the influent pipe to radial flow along the underside of dome 26 a critical factor is the fluid velocity of influent liquid 24 which for good mixing should impinge on the fluid deflector assembly at a velocity between about 2 fps and about 15 fps with an optimal velocity of about 6 fps i e 2 meters second as flow varies with the square of the pipe id an increase in the influent pipe diameter from 2 inches to 4 inches would increase flow about four fold as flow velocity is held constant e g to 320 gpm to maintain a 6 fps influent velocity as flow also scales linearly with the influent velocity for a given pipe diameter reducing influent flow velocity.