I hiked the south rim in 1986 with my son. At the time there were only 2 trails to the bottom. The south Kaibab Trail and the Bright Angel trail. We took the Bright Angel Trail to the bottom. This was a distance of 4.6 miles to the ranger station. It was a few miles farther to the river and Phantom Ranch where you could spend the night and have steak dinner if you made revervations. The total round trip back to the south rim was 9.2 miles. There were only 2 water stations on the way down that were spaced out every 1.5 miles. They said that the estimated time for hiking was 2 hours down and 4 hours up. We made it down in 2 hours all right. But it took me 7 hours up. I was "racked" up 3 days afterwards. My wife had to drive home. There was also a North Kaibab Trail on north rim.

Good Luck!!