Although you pass several old logging ponds and cross many creeks along the 4C Trail, the Forest Service states the water is not safe to drink (presumably from heavy metal contaminates). However, caching water along the trail is made easy with access to several Forest Service roads. I recommend caching water where the 4C Trail crosses FS Road 511 near mile 10.
Take FM 227 north out of Ratcliff for 3.5 miles and take a right on CR 1170 (you could also take CR 1165, but it's a rougher road), continue on CR 1170 for 3.5 miles and take a left on CR 1175 (which later becomes FS 511) for 2.8 miles to the trail crossing. There is a small parking area and sign for Walnut Creek Camp. It helps to mark your water container with the date you plan to pick it up just in case someone comes across it. I usually cache a gallon and write on it with a sharpie. I refill my Camelbak or Nalgenes and then pack the remainder of the gallon on to Walnut Creek Camp and either use it for cleaning or as backup water for another hiker. I met a backpacker on the trail that did not cache water and ran out at Walnut Creek Camp - my extra water was well received.