The ornamental design for a water-saving valve, as shown and described.
FIG. 1 is a perspective view of a water-saving valve showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is an operational perspective view thereof showing that the water-saving valve is mounted on a faucet.
The broken lines shown are included for the purpose of illustrating environment and unclaimed portions of the article and form no part of the claimed design.