I have a buddy who needs a 20 amp GFCI about 300 feet outside from his house to power A pond waterfall and low volt lights. He needs all 20 amps. Actually only about 14 but the start up amps for the pump are like 20 amps. Anyway I heard that every 100 feet we should up the wire size, to accomodate voltage drop. I can't find it in the code book. Do I have to run #6 wire out there. Please help Thank You