Underdrain filter system

Claim 1

A modular underdrain filtration system for filtering a selected liquid comprising: a container having a horizontal support base and continuous sides extending above said support base to a selected height, said container being made of a material impervious and inert with respect to the liquid being filtered, said support base including means for routing the liquid in a selected direction and said container sides defining an aperture for allowing the escape of the said filtered liquid; a multiplicity of support members rigidly attached to said horizontal support base and extending to the interior of said container, said support members being made of a material substantially inert with respect to said liquid being filtered, said support members comprising adjustable anchor bolts which include a first portion rigidly attached to said support base at one end and threaded on the other end, a second portion threaded on its first end and having a second end suitable for securing plates thereto, a sleeve having a first set of threads cut at one end for mating with said threaded end of said first portion, and a second set of threads cut at the second end of said sleeve for mating with said threads on said first end of said second portion, said threads on said sleeve and said first and second portions being arranged such that the length of said anchor bolt can be adjusted by turning said sleeve on its longitudinal axis; a plurality of non-porous plates, each of said plurality of non-porous plates defining a multiplicity of perforations and each said plate being rigidly attached to said support members at selected ones of said perforations, said non-porous perforated plates being made of material substantially inert with respect to said filtered liquid, and being oriented such that they form a continuous plane parallel to said horizontal support base and at a selected distance therefrom, and such that said continuous plane extends between said continuous sides; and a filtration medium located above and supported by said non-porous perforated plates such that the liquid to be filtered percolates down through said filtration medium to said perforated plates, said liquid then flowing through said multiplicity of perforations into the space defined by said perforated plates and said container support base and sides, said liquid then being routed by said routing means through said aperture and out of said container.

Claim 5

The system of claims 1 or 2 wherein said perforated plates are made of material selected from the group consisting of polyvinyl chloride (PVC), fiberglass, stainless steel and copper.

Claim 6

The system of claims 1 or 2 wherein said filtration medium comprises: a plurality of layers of gravel, each layer of gravel being of a selected size; a layer of sand; and a layer of anthricite coal.

Claim 7

The system of claims 1 or 2 wherein said perforated plates are made of a non-porous material selected from the group consisting of polyvinyl chloride (PVC), fiberglass, stainless steel and copper; and wherein said filtration medium comprises a plurality of layers of gravel, each layer of gravel being of a selected size; a layer of sand; and a layer of anthricite coal.