Patent ID: 8388843

Claim:
A method of forming a serial filtration device having opposing open and closed ends, including two or more concentric cylindrical filter layers wherein each filter layer is capable of being independently integrity tested before being assembled into the filtration device, comprising the steps of: a. forming a first filter layer having first and second vertical edges by bonding said edges together in a liquid tight arrangement; b. bonding a first endcap, having inner and outer edges, to a first horizontal end of the first filter layer; c. bonding a second endcap, having inner and outer edges, to a second horizontal-end of the first filter layer; d. testing the integrity of the first filter layer formed in steps (a) to (c); e. forming a second filter layer having third and fourth vertical edges by bonding said edges together in a liquid tight arrangement; f. bonding a third endcap, having inner and outer edges, to a third horizontal end of the second filter layer; g. bonding a fourth endcap, having inner and outer edges, to a fourth horizontal end of the second filter layer; h. testing the integrity of the second layer formed in steps (c) to (g); i. arranging the first filter layer concentrically around a porous core; j. arranging a porous spacer layer concentrically around the first filter layer; k. arranging the second filter layer concentrically around the porous spacer layer; l. bonding the outer edges of the first endcap to the inner edges of the third endcap; m. bonding the outer edges of the second endcap to the inner edges of the fourth endcap; n. binding the porous spacer layer to the third and fourth endcaps of the second filter layer; o. arranging a cylindrical porous outermost housing arranged concentrically around the outer periphery of the second filter layer; and p. bonding the housing to the third, and fourth endcaps; wherein the core, first filter layer, porous spacer layer second filter layer and outermost housing being bonded together selected from the group consisting of solvent bonding, adhesive bonding, heat bonding and ultrasonic bonding, in a liquid tight manner such that all liquid entering the second filter layer must flow through the first filter layer before reaching the core and then the outlet.