I have a gutter downspout in my backyard that leads to a 4" clay drain which leads to the municipal sewer line. Currently the opening sits at ground level. I'd like to raise the ground level a few inches to provide more of a grade away from the building. How can I raise the opening such that it is a tight connection that will NOT allow earth infill to go down the drain?
In the picture, you'll note plastic adapters that connect rain gutter to drain (which would not prevent dirt/sand from going down the drain if I raised ground level).
UPDATE: Thanks for the comments. To clarify, I'm concerned that the plastic adapter (lower, yellowed plastic piece in picture) does NOT provide a tight enough connection to the drain and that it would lead to dirt/sand getting into the drain. I'm OK with the gap between the bottom of gutter downspout and the rectangular-to-round adapter (for now).
As to some comments, I'm not looking to change the grade of the pipe, but rather the grade of the soil/mulch to allow for better water runoff away from the building (water that doesn't go in the gutter/drain). Also in this neighborhood, it is a combined sewer/storm system.