Federal regulations restrict any single showerhead to 2.5gpm (this is measured at a specific pressure). So, if you only have two possible on at one time, a 1/2" line should be okay. If you want to add stuff like body sprays, or an additional head, it would not. If your house pressure is marginal, no supply will produce your desired effects. Don't expect high pressure out of a rainhead...it isn't very forceful.