An ornamentaldesign for an automatic drain valve, as shown and described.
FIG. 1 is a perspective of an automatic drain valve of the present invention;
FIG. 2 is a perspective of the automatic drain valve as viewed in a different orientation;
FIG. 3 is a front elevation of the automatic drain valve;
FIG. 4 is a right side elevation of the automatic drain valve;
FIG. 5 is a top plan of the automatic drain valve;
FIG. 6 is a left side elevation of the automatic drain valve;
FIG. 7 is a rear elevation of the automatic drain valve; and,
FIG. 8 is a bottom plan of the automatic drain valve.
The broken lines shown in the figures are for the purpose of illustrating portions of the automatic drain valve and form no part of the claimed design.