This is a great trail in Shenandoah National Park, but is pretty difficult given the change in elevation. It's at least 2.8 miles out-and-back if you take the same trail. Or you can extend the hike to 3.3 miles by taking the South River Fire Rd Trail back (recommended).
The trail has a fairly steep grade downhill for the first 0.7 miles (including switchbacks). Once you get to the bottom of the switchbacks, the trail runs along the South River for about 0.7 miles until you reach the waterfall overlook.
I suggest taking the South River Fire Rd Trail back to the parking area (2 miles one-way) since it's less steep than this one on; however, it's a slightly longer journey.
Bring lots of water and plan to hike at least 2.8 miles out-and-back.