I don't believe so. If the piezo is flowing, it is being controlled by saturated material with positive pore pressure. Capillarity will have nothing to do with it.
What are you analyzing? Off hand, the only situation I can think of where you would correct a piezometer reading for capillarity is if you are trying to identify the top of saturated material, as opposed to the elevation of zero pressure, commonly assumed to be the piezometric line for stability analysis.
