Unitary Filter Tank And An Underdrain For Filtering A Body Of Water

Abstract

Exemplary embodiments include a unitary pool filter tank and/or an underdrain for a pool filter unit. Embodiments of the unitary pool filter tank can have an integrally formed housing and base. The filter tank can be formed using a blow molding process in which the base of the filter tank is includes a support section and a punted section that has an underdrain mounting member. Embodiments of the underdrain can be formed by interlocking top and bottom components. The top and bottom components can be interlocked by inter-component locking structures.

1 . A method of forming a unitary filter tank having an integral housing and base, the unitary filter tank being configured to filter pool water using sand, the method comprising:
 forming a molten polymer body with a mold, the mold having a housing formation area to form the housing of a unitary filter tank, a base formation area to form the base of the unitary filter tank, and transition points separating the housing formation area from the base formation area;   forcing air into the molten polymer body to urge the molten polymer body to conform to the mold; and   urging the molten polymer body inward towards an interior of the molten polymer body in the base formation area to form a punted section of the base, the punted section forming a generally convex inner wall of the unitary filter tank with a bumped out portion formed about a center axis of the filter tank.   
     
     
         2 . The method of  claim 1 , further comprising forming an inward bend in the molten polymer body about the transition points. 
     
     
         3 . The method of  claim 2 , wherein the base formation area includes base formation molders. 
     
     
         4 . The method of  claim 3 , further comprising urging the base formation molders against the molten polymer body after the mold is closed to form a first outward bend in the molten polymer body between the base formation molders and the transition points to define an outer surface of the base. 
     
     
         5 . The method of  claim 4 , further comprising further urging the base formation molders against the molten polymer body after the mold is closed to form a second outward bend in the molten polymer body to define an under surface and the punted section of the base. 
     
     
         6 . The method of  claim 3 , wherein each of the base formation molders have a contoured surface such that when the mold is closed, the base formation molders form a curved surface configured to extend into a cavity of the mold. 
     
     
         7 . The method of  claim 6 , further comprising urging the base formation molders against the molten polymer body so that the molten polymer body conforms to the contoured surface of the base formation molders to form the punted section of the base. 
     
     
         8 . The method of  claim 7 , further comprising moving the base formation molders into the cavity of the mold towards the transition points to press the punted section into a cavity of the mold so that a portion of the punted section extends into the housing formation area of the mold. 
     
     
         9 . The method of  claim 1 , wherein the molten polymer body cools and hardens to form the unitary filter tank, and the method further comprises releasing the unitary filter tank from the mold. 
     
     
         10 . The method of  claim 1 , wherein the molten polymer body is formed of a high density polyethylene. 
     
     
         11 - 19 . (canceled) 
     
     
         20 . An system for forming a pool filter tank comprising:
 a mold having an open position to receive a molten polymer parison and a closed position to form a molten polymer body from the molten polymer parison,   the mold including a housing formation area having housing formation molders, a base formation area having base formation molders, and transition points separating the housing formation area from the base formation area,   the housing formation molders being spaced away from each other in the open position and being proximate to each other in the closed position,   the base formation molders being spaced away from each other and away from the transition points in the open position, the base formation molders being proximate to each other in the closed position and being moveable towards or away from the transition points to form the base portion of the pool filter tank.   
     
     
         21 . The system of  claim 20 , wherein the transition points are configured to form an inward bend in the molten polymer body. 
     
     
         22 . The system of  claim 20 , where in the base formation molders have a contoured surface configured to form an outward bend in the polymer body. 
     
     
         23 - 29 . (canceled)