I agree with a few other posters. For one I do not believe you can actually claim a point off a foot fault in rec league tennis. One can warn but it must be blatantly obvious. (I am too lazy to look up the actual rules)
You can call it, but only after warning and making other attempts to resolve it by getting an official (which usually isn't possible). Here is the language from the code:
23. Avoid foot faults. Players should not foot fault because it violates the ITF
Rules of Tennis. It is a foot fault when a foot just touches the line, even when the
player does not follow the serve to the net.
24. Calling foot faults. The receiver or the receiver’s partner may call foot faults
only after all reasonable efforts, such as warning the server and attempting to get an
official to the court, have failed and the foot fault is so flagrant as to be clearly
perceptible from the receiver’s side.
Key words are "may call" and "so flagrant as to be clearly perceptible". An opponent is not obligated to call them, and player's thresholds for clearly perceptible will obviously vary. But they
may be called if the steps above are followed.