I am trying to install a new compression shut off valve onto copper pipe coming from the floor for my toilet. I followed the directions and handtightened and then did about a 1/2 turn with the wrench. It feels nice and snug on the pipe but when I turned the water back on to test it I got water leaking out. Should I try tightening more? I know it says not to overtighten so I was worried about that. I didn't put anything on it this time, no tape or pipe compound. It's brand new copper pipe that we cut open (it had been capped) with a pipe cutter.

Thanks.