Dual filtering system for swimming pools

A dual filtering system comprising means designed for providing both sand and diatomaceous earth filtration by which dirt and any large particulates are removed from a liquid feed by passing the liquid feed through a sand filter medium and minute impurities are then removed by passing the liquid filtrate through a diatomaceous earth filter medium, including:

• a tank having a removable cover having first and second body sections which are separated by a plate therebetween, each of said body sections having an inlet opening for receiving liquid to be filtered and first and second outlet openings for discharging liquid filtrate, said plate having an opening therein;
• a check valve means interposed in the plate opening and capable of controlling flow of fluids through said plate opening from the interior of said second tank section into the interior of said first tank section when the pressure in said second tank section exceeds the pressure in said first tank section by a preselected amount, said check valve means including a seal means for separating and sealing the first tank section from said second tank section;
• a central manifold disposed in the first body section of said tank, having an outlet means in communication with said first outlet opening of said first tank section and in communication with a plurality of filter grid units, said manifold including means for supporting the filter grid units relative to one another comprising a central hub having a cylindrical side wall, a plurality of support arms which are removably connected to and extend radially from the side wall of the central hub in a plane perpendicular to the longitudinal axis of the central hub, each of the support arms having a plurality of threaded openings therein which are spaced apart from one another and adapted to receive respective threaded ends of said filter grid units in said tank and vertically align said filter grid units in a densely packed but non-touching array;
• said filter grid units disposed in said tank in the path of said liquid being rigid and stationary, each of said filter grid units comprising a perforated support frame, and a permeable filter tube, said tube being in the form of a braided, essentially non-extensible tubular member encasing and sealed to said support frame, and in registry therewith, said tubular member being closed at one end and open at its other end, said open end of said filter grid being threaded and removably connected to a threaded opening in one of said support arms;
• the interstices of said braided filter tube capable of passing liquid but not passing diatomaceous earth particles;
• said second tank section having disposed therein:
• a filter bed of sand, a diffuser element adapted for distributing fluids to be filtered into said second tank section, said diffuser element being close to the upper end of, and in communication with the inlet of, said second tank section, and an underdrain for removing fluids but not the sand bed from the second tank section, said underdrain being close to the base of, and in communication with, a first outlet of said second tank section;
• pump means in fluid communication with each of said inlet and outlet openings in said first and second tank sections for circulating liquid into and out of each of said first and second tank sections through said filter grid units and said central manifold in said first tank section and/or through a sand bed in said second tank section and also in fluid communication with outlet lines for passage externally of said system by-passing said first and/or second tank sections;
• first valve means disposed between said pump means and said first tank section for controlling flow of said liquid into and out of said first tank section and through said filter grid units and central manifold and for controlling flow of said liquid by-passing said first tank section;
• and
• second valve means disposed between said first valve means, said second tank section and said punp means for controlling flow of said liquid into and out of said second tank section and through said sand bed filtration zone and for controlling flow of said liquid by-passing said second tank section.

A dual filtration system comprising means designed for providing two separate zones of filtering a liquid containing particulate contaminants one filtering zone above the other, in which the pressure differential between the two zones is automatically regulated, including:

• a. a tank having a fixed body in two sections which are separated by a plate therebetween the sections and a removable cover for a first one of said sections, each of said sections having an inlet port in its upper end and an outlet port in its lower end;
• pressure balancing means establishing fluid communication between the first and second tank sections;
• check valve means associated with said pressure balancing means and responsive to a preselected pressure differential between said first and second tank sections for controlling flow of fluids through said pressure balancing means from said second tank section to the first tank section when said pressure differential exceeds said preselected amount, said check valve means including a sealing means for separating and sealing the first tank section from the second tank section;
• b. a rerovable filter assembly disposed within said first tank section, said filter assembly comprised of a manifold assembly and a plurality of like, vertically disposed filter grid units of cylindrical shape;
• said manifold assembly including a cylindrical hub having a plurality of detachably connected radial support arms and a conduit arm extending therefrom in a plane perpendicular to the longitudinal axis of the hub, said conduit arm being in fluid communication with said outlet port in said first tank section, said support arms having openings uniformly disposed in upper surfaces thereof adapted to be detachably connected to ends of said filter grid units;
• each of said filter grid units having a rigid, nonbendable and perforated plastic tubular inner sleeve enclosed within a fine resh plastic tubular outer sleeve capable of passing water and retaining diatomaceous earth Particles in its interstices, the perforations being uniformly spaced circumferentially and longitudinally about said inner sleeve, said inner sleeve being coaxial with said outer sleeve and fixedly disposed relative thereto and forming said unitary grid unit therewith, said filter grid units having imperforate tops and bottom connecting means which are adapted to threadably connect said units with said opening in said support arms;
• said filter unit and manifold assembly being disposed in a flow path of a liquid passing into and out of said first tank section;
• c. a pump in fluid communication with an inlet line for the liquid to be filtered, with said inlet and outlet ports in said first and second tank sections, and with associated return and waste lines for said first and second tank sections, said pump means being capable of causing said liquid to flow into and out of respective inlet and outlet ports of said first and second tank section, repectively, through said filter unit and manifold assembly and/or said sand bed and out through return or waste lines, or from said first tank section to said second tank section, and further being capable of causing said liquid to by-pass said first and/or second tank sections and flow out of said return or waste lines:
• d. a first multifunctional valve means in fluid communication with said pump means, with said ports in said first tank section and with return and waste lines associated therewith and having:
• a first control means having open and closed states and capable of controlling the flow of said liquid into the inlet port of said first tank section through said filter unit and manifold assembly and the outlet port of said first tank sections, and out through the return line of said first valve neans;
• a second control means having open and closed states and capable of controlling the flow of said liquid into the outlet port of said first tank section, through said filter unit and manifold assembly and said inlet port of said first tank section, and out through the waste line of said first valve means:
• a third control means having open and closed states and capable of controlling the flow of said liquid by-passing said first valve means;
• a fourth control means having open and closed states and capable of controlling the flow of said liquid by-passing said first tank section out of the waste line of said first valve means;
• and
• means for moving each of said first, second, third and fourth control means between their respective open and closed states.
• e. a second multifunctional valve means in fluid communication with said pump means, with said ports in said second tank section and with return and waste lines associated therewith and with first and second inlet lines for said first valve means, and having:
• a first control means having open and closed states and capable of controlling the flow of said liquid into the inlet port of said second tank section through said sand bed and the outlet port of said second tank section, and out through the return line of said valve means;
• a second control means having open and closed states and capable of controlling the flow of said liquid into the outlet port of said second tank section, through said sand bed and said inlet port of said second tank section, and out through the waste line of said second valve means;
• a third control means having open and closed states and capable of controlling the flow of said liquid into the inlet port of said second tank section through said sand bed and the outlet port of said second tank section, and out through a first inlet line of said first valve means;
• a fourth control means having open and closed states and capable of controlling the flow of said liquid by-passing said second tank section out of the return line of said second valve means;
• a fifth control means having open and closed states and capable of controlling the flow of said liquid by-passing said second tank section and out through a second inlet line of said first valve means;
• and
• a sixth control means having open and closed states and capable of controlling the flow of said liquid by-passing said second tank section and out of the waste line of said second valve means.