Fluid filtering apparatus and method of making the same

A fluid pressure vessel has a chamber with an inlet and outlet with a nested primary and secondary filter bag disposed such that the primary bag communicates exclusively with the inlet, and flow through the primary bag flows through the secondary bag before the outlet. The primary bag is disposed in a first rigid porous basket and the bag rim seals against a flange on the first basket. The secondary filter bag surrounds the first basket and the rim of the secondary bag is sealed around the flange of first basket. A second rigid porous basket surrounds the secondary filter bag and is sealed on the rim of the secondary filter bag and is sealed against the inner periphery of the pressure chamber by an O-ring.