Self-cleaning, groutless, filter underdrain

An underdrain filtering system comprising:

• at least one underdrain lateral secured to a filter floor that is formed by one or a plurality of underdrain blocks that each independently comprise a top wall, a bottom wall, and two side walls connecting the top wall to the bottom wall to define an internal chamber,
• wherein the bottom wall, or a lower portion of at least one side wall, or both, comprises a plurality of orifices and wherein the underdrain lateral is spaced apart from the filter floor to allow liquid and/or solid materials to enter and exit the internal chamber, and
• wherein the bottom wall of the at least one underdrain block comprises internal channels formed through an inner surface of the bottom wall, and wherein the orifices are positioned within the channels.

An underdrain block comprising a top wall, a bottom wall, two side walls connecting the top wall to the bottom wall to define an internal chamber, and an internal wall that extends between the side walls to form a first zone and a second zone, wherein the first zone is formed between the top wall, the side walls, and the internal wall, and the second zone is formed between the bottom wall, the side walls, and the internal wall, and

• wherein the bottom wall comprises orifices that allow liquid and solid materials to enter and exit the internal chamber, and the side walls of the first zone comprise additional orifices, and the side walls of the second zone are free of orifices.