The ornamental design for a drain apparatus, as shown and described.
FIG. 1 is a top-side isometric view of a drain apparatus;
FIG. 2 is an exploded top-side isometric view thereof;
FIG. 3 is a bottom-side isometric view thereof;
FIG. 4 is a first side view thereof;
FIG. 5 is a second side view thereof;
FIG. 6 is a third side view thereof;
FIG. 7 is a fourth side view thereof;
FIG. 8 is a top view thereof; and,
FIG. 9 is a bottom view thereof.
The dashed broken lines shown in the drawings illustrate portions of the drain apparatus that form no part of the claim. The dash-dot-dash broken lines in the drawings depict boundaries of the claim and form no part of the claim.