A diffuser configured to receive water having a velocity and for introducing said water near the bottom or the top of a water tank, said diffuser comprising: a bowl with a flat center and domed around the perimeter, the bowl having a first hole in the center of the bowl ; a cylindrical deflection element having a first end and a second end, said first end being further equipped with a plurality of extending arms , and said second end being equipped with a second hole ; a circular lid to be configured to be able to close either the first hole or the second; a cylindrical pipe with a first and second end, said first end being configured to be attached to a pipe , and said second end being equipped with third hole; wherein the cylindrical deflection element is, by means of one end of its extending arms , concentrically attached to the inner surface of the bowl ; further characterized in that the cylindrical pipe is attached to the first hole of the bowl , the circular lid is attached to the second hole of the cylindrical deflection element , or, the cylindrical pipe is attached to the second hole of the cylindrical deflection element , the circular lid is attached to the first hole of the bowl , the cylindrical pipe has, furthermore, a radially extending lip at the first end, and, the radially extending lip is configured to engage with either the first hole of the bowl or the second hole of the cylindrical deflection element , characterized in that the diameter of the flat on the bowl is identical to the diameter of a virtual circle of the cylindrical deflection element , wherein the virtual circle means a circle that is drawn so that all the plurality of extending arms are inside of the circle. a bowl with a flat center and domed around the perimeter, the bowl having a first hole in the center of the bowl ; a cylindrical deflection element having a first end and a second end, said first end being further equipped with a plurality of extending arms , and said second end being equipped with a second hole ; a circular lid to be configured to be able to close either the first hole or the second; a cylindrical pipe with a first and second end, said first end being configured to be attached to a pipe , and said second end being equipped with third hole; wherein the cylindrical deflection element is, by means of one end of its extending arms , concentrically attached to the inner surface of the bowl ; further characterized in that the cylindrical pipe is attached to the first hole of the bowl , the circular lid is attached to the second hole of the cylindrical deflection element , or, the cylindrical pipe is attached to the second hole of the cylindrical deflection element , the circular lid is attached to the first hole of the bowl , the cylindrical pipe has, furthermore, a radially extending lip at the first end, and, the radially extending lip is configured to engage with either the first hole of the bowl or the second hole of the cylindrical deflection element , characterized in that the diameter of the flat on the bowl is identical to the diameter of a virtual circle of the cylindrical deflection element , wherein the virtual circle means a circle that is drawn so that all the plurality of extending arms are inside of the circle. <EOS>